speculative : add tree-based sampling example (#3624)

* sampling : one sequence per sampling context

ggml-ci

* speculative : add tree-based sampling support

ggml-ci

* speculative : reuse the n_parallel CLI param

* speculative : refactor sampling

* examples : fix build after sampling refactoring

ggml-ci

* batched : fix n_seq_id

* sampling : fix malloc

ggml-ci

* swift : fix build

ggml-ci

* swift : try to fix build

ggml-ci

* prompts : add assistant.txt

* common : add llama_batch_add() and llama_batch_clear() helpers

* speculative : minor refactor

ggml-ci

* minor : comments + rename

ggml-ci

* speculative : fix off-by-one for n_drafted

* speculative : fix the n_drafted fix + p constants

12 files changed, 369 insertions, 363 deletions

diff --git a/examples/batched-bench/batched-bench.cpp b/examples/batched-bench/batched-bench.cpp
index 3e1e0716..c552eaa7 100644
--- a/examples/batched-bench/batched-bench.cpp
+++ b/examples/batched-bench/batched-bench.cpp
@@ -114,7 +114,7 @@ int main(int argc, char ** argv) {
         return 1;
     }
 
-    llama_batch batch = llama_batch_init(n_kv_max, 0);
+    llama_batch batch = llama_batch_init(n_kv_max, 0, 1);
 
     // decode in batches of ctx_params.n_batch tokens
     auto decode_helper = [](llama_context * ctx, llama_batch & batch, int32_t n_batch) {
@@ -123,11 +123,12 @@ int main(int argc, char ** argv) {
 
             llama_batch batch_view = {
                 n_tokens,
-                batch.token  + i,
+                batch.token    + i,
                 nullptr,
-                batch.pos    + i,
-                batch.seq_id + i,
-                batch.logits + i,
+                batch.pos      + i,
+                batch.n_seq_id + i,
+                batch.seq_id   + i,
+                batch.logits   + i,
                 0, 0, 0, // unused
             };
 
@@ -143,13 +144,8 @@ int main(int argc, char ** argv) {
 
     // warm up
     {
-        batch.n_tokens = 16;
-
-        for (int i = 0; i < batch.n_tokens; ++i) {
-            batch.token[i]  = 0;
-            batch.pos[i]    = i;
-            batch.seq_id[i] = 0;
-            batch.logits[i] = false;
+        for (int i = 0; i < 16; ++i) {
+            llama_batch_add(batch, 0, i, { 0 }, false);
         }
 
         if (!decode_helper(ctx, batch, ctx_params.n_batch)) {
@@ -174,13 +170,12 @@ int main(int argc, char ** argv) {
                     continue;
                 }
 
-                batch.n_tokens = is_pp_shared ? pp : pl*pp;
+                llama_batch_clear(batch);
+
+                const int n_tokens = is_pp_shared ? pp : pl*pp;
 
-                for (int i = 0; i < batch.n_tokens; ++i) {
-                    batch.token[i]  = 0;
-                    batch.pos[i]    = i;
-                    batch.seq_id[i] = 0;
-                    batch.logits[i] = false;
+                for (int i = 0; i < n_tokens; ++i) {
+                    llama_batch_add(batch, 0, i, { 0 }, false);
                 }
                 batch.logits[batch.n_tokens - 1] = true;
 
@@ -204,13 +199,10 @@ int main(int argc, char ** argv) {
                 const auto t_tg_start = ggml_time_us();
 
                 for (int i = 0; i < tg; ++i) {
-                    batch.n_tokens = pl;
+                    llama_batch_clear(batch);
 
                     for (int j = 0; j < pl; ++j) {
-                        batch.token[j]  = 0;
-                        batch.pos[j]    = pp + i;
-                        batch.seq_id[j] = j;
-                        batch.logits[j] = true;
+                        llama_batch_add(batch, 0, pp + i, { j }, true);
                     }
 
                     if (!decode_helper(ctx, batch, ctx_params.n_batch)) {
diff --git a/examples/batched.swift/Sources/main.swift b/examples/batched.swift/Sources/main.swift
index 05d1bb9d..77273038 100644
--- a/examples/batched.swift/Sources/main.swift
+++ b/examples/batched.swift/Sources/main.swift
@@ -69,7 +69,7 @@ for id: llama_token in tokens {
 
 print("\n")
 
-var batch = llama_batch_init(max(Int32(tokens.count), Int32(n_parallel)), 0)
+var batch = llama_batch_init(max(Int32(tokens.count), Int32(n_parallel)), 0, 1)
 defer {
     llama_batch_free(batch)
 }
@@ -80,7 +80,12 @@ batch.n_tokens = Int32(tokens.count)
 for (i, token) in tokens.enumerated() {
     batch.token[i] = token
     batch.pos[i] = Int32(i)
-    batch.seq_id[i] = 0
+    batch.n_seq_id[i] = 1
+    // batch.seq_id[i][0] = 0
+    // TODO: is this the proper way to do this?
+    if let seq_id = batch.seq_id[i] {
+        seq_id[0] = 0
+    }
     batch.logits[i] = 0
 }
 
@@ -169,7 +174,10 @@ while n_cur <= n_len {
         // push this new token for next evaluation
         batch.token[Int(batch.n_tokens)] = new_token_id
         batch.pos[Int(batch.n_tokens)] = n_cur
-        batch.seq_id[Int(batch.n_tokens)] = Int32(i)
+        batch.n_seq_id[Int(batch.n_tokens)] = 1
+        if let seq_id = batch.seq_id[Int(batch.n_tokens)] {
+            seq_id[0] = Int32(i)
+        }
         batch.logits[Int(batch.n_tokens)] = 1
 
         i_batch[i] = batch.n_tokens
diff --git a/examples/batched/batched.cpp b/examples/batched/batched.cpp
index a88e022d..15521216 100644
--- a/examples/batched/batched.cpp
+++ b/examples/batched/batched.cpp
@@ -97,20 +97,15 @@ int main(int argc, char ** argv) {
 
     fflush(stderr);
 
-    // create a llama_batch with size 512
+    // create a llama_batch
     // we use this object to submit token data for decoding
-
-    llama_batch batch = llama_batch_init(std::max(tokens_list.size(), (size_t)n_parallel), 0);
+    llama_batch batch = llama_batch_init(std::max(tokens_list.size(), (size_t)n_parallel), 0, 1);
 
     // evaluate the initial prompt
-    batch.n_tokens = tokens_list.size();
-
-    for (int32_t i = 0; i < batch.n_tokens; i++) {
-        batch.token[i]  = tokens_list[i];
-        batch.pos[i]    = i;
-        batch.seq_id[i] = 0;
-        batch.logits[i] = false;
+    for (size_t i = 0; i < tokens_list.size(); ++i) {
+        llama_batch_add(batch, tokens_list[i], i, { 0 }, false);
     }
+    GGML_ASSERT(batch.n_tokens == (int) tokens_list.size());
 
     // llama_decode will output logits only for the last token of the prompt
     batch.logits[batch.n_tokens - 1] = true;
@@ -146,7 +141,7 @@ int main(int argc, char ** argv) {
 
     while (n_cur <= n_len) {
         // prepare the next batch
-        batch.n_tokens = 0;
+        llama_batch_clear(batch);
 
         // sample the next token for each parallel sequence / stream
         for (int32_t i = 0; i < n_parallel; ++i) {
@@ -198,15 +193,10 @@ int main(int argc, char ** argv) {
 
             streams[i] += llama_token_to_piece(ctx, new_token_id);
 
-            // push this new token for next evaluation
-            batch.token [batch.n_tokens] = new_token_id;
-            batch.pos   [batch.n_tokens] = n_cur;
-            batch.seq_id[batch.n_tokens] = i;
-            batch.logits[batch.n_tokens] = true;
-
             i_batch[i] = batch.n_tokens;
 
-            batch.n_tokens += 1;
+            // push this new token for next evaluation
+            llama_batch_add(batch, new_token_id, n_cur, { i }, true);
 
             n_decode += 1;
         }
diff --git a/examples/embd-input/embd-input-lib.cpp b/examples/embd-input/embd-input-lib.cpp
index 87a5a1c2..3ce33842 100644
--- a/examples/embd-input/embd-input-lib.cpp
+++ b/examples/embd-input/embd-input-lib.cpp
@@ -79,7 +79,7 @@ bool eval_float(void * model, float * input, int N){
         if (n_eval > n_batch) {
             n_eval = n_batch;
         }
-        llama_batch batch = {  int32_t(n_eval), nullptr, (input+i*n_emb), nullptr, nullptr, nullptr, n_past, 1, 0, };
+        llama_batch batch = {  int32_t(n_eval), nullptr, (input+i*n_emb), nullptr, nullptr, nullptr, nullptr, n_past, 1, 0, };
         if (llama_decode(ctx, batch)) {
             fprintf(stderr, "%s : failed to eval\n", __func__);
             return false;
diff --git a/examples/infill/infill.cpp b/examples/infill/infill.cpp
index 187623f5..128d6708 100644
--- a/examples/infill/infill.cpp
+++ b/examples/infill/infill.cpp
@@ -257,12 +257,12 @@ int main(int argc, char ** argv) {
 
     LOG("prefix: \"%s\"\n", log_tostr(params.input_prefix));
     LOG("suffix: \"%s\"\n", log_tostr(params.input_suffix));
-    LOG("tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp));
+    LOG("tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp).c_str());
 
     // Should not run without any tokens
     if (embd_inp.empty()) {
         embd_inp.push_back(llama_token_bos(ctx));
-        LOG("embd_inp was considered empty and bos was added: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp));
+        LOG("embd_inp was considered empty and bos was added: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp).c_str());
     }
 
     // Tokenize negative prompt
@@ -273,10 +273,10 @@ int main(int argc, char ** argv) {
         LOG("cfg_negative_prompt: \"%s\"\n", log_tostr(sparams.cfg_negative_prompt));
 
         guidance_inp = ::llama_tokenize(ctx_guidance, sparams.cfg_negative_prompt, add_bos);
-        LOG("guidance_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_guidance, guidance_inp));
+        LOG("guidance_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_guidance, guidance_inp).c_str());
 
         std::vector<llama_token> original_inp = ::llama_tokenize(ctx, params.prompt, add_bos);
-        LOG("original_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, original_inp));
+        LOG("original_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, original_inp).c_str());
 
         original_prompt_len = original_inp.size();
         guidance_offset = (int)guidance_inp.size() - original_prompt_len;
@@ -294,8 +294,8 @@ int main(int argc, char ** argv) {
         params.n_keep = (int)embd_inp.size();
     }
 
-    LOG("inp_pfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_pfx));
-    LOG("inp_sfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_sfx));
+    LOG("inp_pfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_pfx).c_str());
+    LOG("inp_sfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_sfx).c_str());
 
 
     // enable interactive mode if interactive start is specified
@@ -388,9 +388,6 @@ int main(int argc, char ** argv) {
             grammar_rules.data(), grammar_rules.size(), parsed_grammar.symbol_ids.at("root"));
     }
 
-    // TODO: replace with ring-buffer
-    std::vector<llama_token> last_tokens(n_ctx);
-    std::fill(last_tokens.begin(), last_tokens.end(), 0);
     LOG_TEE("\n#####  Infill mode  #####\n\n");
     if (params.infill) {
         printf("\n************\n");
@@ -433,11 +430,7 @@ int main(int argc, char ** argv) {
     std::vector<llama_token> embd;
     std::vector<llama_token> embd_guidance;
 
-    const int n_vocab = llama_n_vocab(model);
-
-    llama_sampling_context ctx_sampling = llama_sampling_context_init(params, grammar);
-    std::vector<llama_token_data> candidates;
-    candidates.reserve(n_vocab);
+    struct llama_sampling_context * ctx_sampling = llama_sampling_init(params);
 
     while (n_remain != 0 || params.interactive) {
         // predict
@@ -484,7 +477,7 @@ int main(int argc, char ** argv) {
 
                 LOG("after swap: n_past = %d, n_past_guidance = %d\n", n_past, n_past_guidance);
 
-                LOG("embd: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd));
+                LOG("embd: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd).c_str());
 
             }
 
@@ -512,7 +505,7 @@ int main(int argc, char ** argv) {
                     input_buf  = embd_guidance.data();
                     input_size = embd_guidance.size();
 
-                    LOG("guidance context: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_guidance));
+                    LOG("guidance context: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_guidance).c_str());
                 } else {
                     input_buf  = embd.data();
                     input_size = embd.size();
@@ -535,7 +528,7 @@ int main(int argc, char ** argv) {
                     n_eval = params.n_batch;
                 }
 
-                LOG("eval: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd));
+                LOG("eval: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd).c_str());
 
                 if (llama_decode(ctx, llama_batch_get_one(&embd[i], n_eval, n_past, 0))) {
                     LOG_TEE("%s : failed to eval\n", __func__);
@@ -554,12 +547,11 @@ int main(int argc, char ** argv) {
 
         if ((int) embd_inp.size() <= n_consumed && !is_interacting) {
 
-            const llama_token id = llama_sampling_sample(ctx, ctx_guidance, ctx_sampling, last_tokens, candidates);
+            const llama_token id = llama_sampling_sample(ctx_sampling, ctx, ctx_guidance);
 
-            last_tokens.erase(last_tokens.begin());
-            last_tokens.push_back(id);
+            llama_sampling_accept(ctx_sampling, ctx, id);
 
-            LOG("last: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, last_tokens));
+            LOG("last: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, ctx_sampling->prev).c_str());
 
             embd.push_back(id);
 
@@ -575,8 +567,8 @@ int main(int argc, char ** argv) {
             LOG("embd_inp.size(): %d, n_consumed: %d\n", (int) embd_inp.size(), n_consumed);
             while ((int) embd_inp.size() > n_consumed) {
                 embd.push_back(embd_inp[n_consumed]);
-                last_tokens.erase(last_tokens.begin());
-                last_tokens.push_back(embd_inp[n_consumed]);
+                ctx_sampling->prev.erase(ctx_sampling->prev.begin());
+                ctx_sampling->prev.push_back(embd_inp[n_consumed]);
                 ++n_consumed;
                 if ((int) embd.size() >= params.n_batch) {
                     break;
@@ -608,7 +600,7 @@ int main(int argc, char ** argv) {
         if ((int) embd_inp.size() <= n_consumed) {
 
             // deal with eot token in infill mode
-            if ((last_tokens.back() == llama_token_eot(ctx) || is_interacting) && params.interactive){
+            if ((ctx_sampling->prev.back() == llama_token_eot(ctx) || is_interacting) && params.interactive){
                 if(is_interacting && !params.interactive_first) {
                     // print an eot token
                     printf("%s", llama_token_to_piece(ctx, llama_token_eot(ctx)).c_str());
@@ -675,7 +667,7 @@ int main(int argc, char ** argv) {
                 is_interacting = false;
             }
             // deal with end of text token in interactive mode
-            else if (last_tokens.back() == llama_token_eos(ctx)) {
+            else if (ctx_sampling->prev.back() == llama_token_eos(ctx)) {
                 LOG("found EOS token\n");
 
                 if (params.interactive) {
@@ -727,7 +719,7 @@ int main(int argc, char ** argv) {
                     const size_t original_size = embd_inp.size();
 
                     const auto line_inp = ::llama_tokenize(ctx, buffer, false);
-                    LOG("input tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, line_inp));
+                    LOG("input tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, line_inp).c_str());
 
                     embd_inp.insert(embd_inp.end(), line_inp.begin(), line_inp.end());
 
diff --git a/examples/llava/llava-utils.h b/examples/llava/llava-utils.h
index 4e71351d..e050b59b 100644
--- a/examples/llava/llava-utils.h
+++ b/examples/llava/llava-utils.h
@@ -17,7 +17,7 @@ inline bool eval_image_embd(llama_context * ctx_llama, float * embd, int N, int
         if (n_eval > n_batch) {
             n_eval = n_batch;
         }
-        llama_batch batch = {int32_t(n_eval), nullptr, (embd+i*n_embd), nullptr, nullptr, nullptr, *n_past, 1, 0, };
+        llama_batch batch = {int32_t(n_eval), nullptr, (embd+i*n_embd), nullptr, nullptr, nullptr, nullptr, *n_past, 1, 0, };
         if (llama_decode(ctx_llama, batch)) {
             fprintf(stderr, "%s : failed to eval\n", __func__);
             return false;
diff --git a/examples/llava/llava.cpp b/examples/llava/llava.cpp
index b24cb2e6..f0974d5b 100644
--- a/examples/llava/llava.cpp
+++ b/examples/llava/llava.cpp
@@ -127,7 +127,7 @@ int main(int argc, char ** argv) {
 
     const int max_tgt_len = params.n_predict < 0 ? 256 : params.n_predict;
 
-    eval_string(ctx_llama, "A chat between a curious human and an artificial intelligence assistant.  The assistant gives helpful, detailed, and polite answers to the human's questions.\nUSER:", params.n_batch, &n_past, true);
+    eval_string(ctx_llama, "A chat between a curious human and an artificial intelligence assistant. The assistant gives helpful, detailed, and polite answers to the human's questions.\nUSER:", params.n_batch, &n_past, true);
     eval_image_embd(ctx_llama, image_embd, n_img_pos, params.n_batch, &n_past);
     eval_string(ctx_llama, (params.prompt + "\nASSISTANT:").c_str(), params.n_batch, &n_past, false);
 
diff --git a/examples/main/main.cpp b/examples/main/main.cpp
index 7313d06a..1a5911c5 100644
--- a/examples/main/main.cpp
+++ b/examples/main/main.cpp
@@ -3,7 +3,6 @@
 #include "console.h"
 #include "llama.h"
 #include "build-info.h"
-#include "grammar-parser.h"
 
 #include <cassert>
 #include <cinttypes>
@@ -245,12 +244,12 @@ int main(int argc, char ** argv) {
     }
 
     LOG("prompt: \"%s\"\n", log_tostr(params.prompt));
-    LOG("tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp));
+    LOG("tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp).c_str());
 
     // Should not run without any tokens
     if (embd_inp.empty()) {
         embd_inp.push_back(llama_token_bos(ctx));
-        LOG("embd_inp was considered empty and bos was added: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp));
+        LOG("embd_inp was considered empty and bos was added: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_inp).c_str());
     }
 
     // Tokenize negative prompt
@@ -261,10 +260,10 @@ int main(int argc, char ** argv) {
         LOG("cfg_negative_prompt: \"%s\"\n", log_tostr(sparams.cfg_negative_prompt));
 
         guidance_inp = ::llama_tokenize(ctx_guidance, sparams.cfg_negative_prompt, add_bos, true);
-        LOG("guidance_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_guidance, guidance_inp));
+        LOG("guidance_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_guidance, guidance_inp).c_str());
 
         std::vector<llama_token> original_inp = ::llama_tokenize(ctx, params.prompt, add_bos, true);
-        LOG("original_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, original_inp));
+        LOG("original_inp tokenized: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, original_inp).c_str());
 
         original_prompt_len = original_inp.size();
         guidance_offset = (int)guidance_inp.size() - original_prompt_len;
@@ -323,8 +322,8 @@ int main(int argc, char ** argv) {
     const auto inp_pfx = ::llama_tokenize(ctx, "\n\n### Instruction:\n\n", add_bos, true);
     const auto inp_sfx = ::llama_tokenize(ctx, "\n\n### Response:\n\n",    false,   true);
 
-    LOG("inp_pfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_pfx));
-    LOG("inp_sfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_sfx));
+    LOG("inp_pfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_pfx).c_str());
+    LOG("inp_sfx: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, inp_sfx).c_str());
 
     // in instruct mode, we inject a prefix and a suffix to each input by the user
     if (params.instruct) {
@@ -421,35 +420,6 @@ int main(int argc, char ** argv) {
     LOG_TEE("generate: n_ctx = %d, n_batch = %d, n_predict = %d, n_keep = %d\n", n_ctx, params.n_batch, params.n_predict, params.n_keep);
     LOG_TEE("\n\n");
 
-    struct llama_grammar * grammar = NULL;
-    grammar_parser::parse_state parsed_grammar;
-
-    if (!params.grammar.empty()) {
-        parsed_grammar = grammar_parser::parse(params.grammar.c_str());
-        // will be empty (default) if there are parse errors
-        if (parsed_grammar.rules.empty()) {
-            return 1;
-        }
-        LOG_TEE("%s: grammar:\n", __func__);
-        grammar_parser::print_grammar(stderr, parsed_grammar);
-        LOG_TEE("\n");
-
-        {
-            auto it = sparams.logit_bias.find(llama_token_eos(ctx));
-            if (it != sparams.logit_bias.end() && it->second == -INFINITY) {
-                LOG_TEE("%s: warning: EOS token is disabled, which will cause most grammars to fail\n", __func__);
-            }
-        }
-
-        std::vector<const llama_grammar_element *> grammar_rules(parsed_grammar.c_rules());
-        grammar = llama_grammar_init(
-            grammar_rules.data(), grammar_rules.size(), parsed_grammar.symbol_ids.at("root"));
-    }
-
-    // TODO: replace with ring-buffer
-    std::vector<llama_token> last_tokens(n_ctx);
-    std::fill(last_tokens.begin(), last_tokens.end(), 0);
-
     if (params.interactive) {
         const char *control_message;
         if (params.multiline_input) {
@@ -489,11 +459,7 @@ int main(int argc, char ** argv) {
     std::vector<llama_token> embd;
     std::vector<llama_token> embd_guidance;
 
-    const int n_vocab = llama_n_vocab(model);
-
-    llama_sampling_context ctx_sampling = llama_sampling_context_init(params, grammar);
-    std::vector<llama_token_data> candidates;
-    candidates.reserve(n_vocab);
+    struct llama_sampling_context * ctx_sampling = llama_sampling_init(params);
 
     while ((n_remain != 0 && !is_antiprompt) || params.interactive) {
         // predict
@@ -540,7 +506,7 @@ int main(int argc, char ** argv) {
 
                 LOG("after swap: n_past = %d, n_past_guidance = %d\n", n_past, n_past_guidance);
 
-                LOG("embd: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd));
+                LOG("embd: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd).c_str());
 
                 LOG("clear session path\n");
                 path_session.clear();
@@ -570,7 +536,6 @@ int main(int argc, char ** argv) {
 
             // evaluate tokens in batches
             // embd is typically prepared beforehand to fit within a batch, but not always
-
             if (ctx_guidance) {
                 int input_size = 0;
                 llama_token * input_buf = NULL;
@@ -592,7 +557,7 @@ int main(int argc, char ** argv) {
                     input_buf  = embd_guidance.data();
                     input_size = embd_guidance.size();
 
-                    LOG("guidance context: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_guidance));
+                    LOG("guidance context: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd_guidance).c_str());
                 } else {
                     input_buf  = embd.data();
                     input_size = embd.size();
@@ -615,7 +580,7 @@ int main(int argc, char ** argv) {
                     n_eval = params.n_batch;
                 }
 
-                LOG("eval: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd));
+                LOG("eval: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, embd).c_str());
 
                 if (llama_decode(ctx, llama_batch_get_one(&embd[i], n_eval, n_past, 0))) {
                     LOG_TEE("%s : failed to eval\n", __func__);
@@ -645,12 +610,11 @@ int main(int argc, char ** argv) {
                 LOG("saved session to %s\n", path_session.c_str());
             }
 
-            const llama_token id = llama_sampling_sample(ctx, ctx_guidance, ctx_sampling, last_tokens, candidates);
+            const llama_token id = llama_sampling_sample(ctx_sampling, ctx, ctx_guidance);
 
-            last_tokens.erase(last_tokens.begin());
-            last_tokens.push_back(id);
+            llama_sampling_accept(ctx_sampling, ctx, id);
 
-            LOG("last: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, last_tokens));
+            LOG("last: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, ctx_sampling->prev).c_str());
 
             embd.push_back(id);
 
@@ -666,8 +630,14 @@ int main(int argc, char ** argv) {
             LOG("embd_inp.size(): %d, n_consumed: %d\n", (int) embd_inp.size(), n_consumed);
             while ((int) embd_inp.size() > n_consumed) {
                 embd.push_back(embd_inp[n_consumed]);
-                last_tokens.erase(last_tokens.begin());
-                last_tokens.push_back(embd_inp[n_consumed]);
+
+                // GG: I'm not sure it's a good idea to push the prompt tokens into the sampling context
+                //     Most likely will remove this in the future to avoid exposing "prev"
+                //     Same thing is done in "server". If we stop pushing the prompt tokens, then the repetition
+                //     penalty will be applied only based on the tokens generated by the model.
+                ctx_sampling->prev.erase(ctx_sampling->prev.begin());
+                ctx_sampling->prev.push_back(embd_inp[n_consumed]);
+
                 ++n_consumed;
                 if ((int) embd.size() >= params.n_batch) {
                     break;
@@ -700,7 +670,7 @@ int main(int argc, char ** argv) {
             // check for reverse prompt
             if (!params.antiprompt.empty()) {
                 std::string last_output;
-                for (auto id : last_tokens) {
+                for (auto id : ctx_sampling->prev) {
                     last_output += llama_token_to_piece(ctx, id);
                 }
 
@@ -729,7 +699,7 @@ int main(int argc, char ** argv) {
             }
 
             // deal with end of text token in interactive mode
-            if (last_tokens.back() == llama_token_eos(ctx)) {
+            if (ctx_sampling->prev.back() == llama_token_eos(ctx)) {
                 LOG("found EOS token\n");
 
                 if (params.interactive) {
@@ -801,7 +771,7 @@ int main(int argc, char ** argv) {
                     const auto line_pfx = ::llama_tokenize(ctx, params.input_prefix, false, true);
                     const auto line_inp = ::llama_tokenize(ctx, buffer,              false, false);
                     const auto line_sfx = ::llama_tokenize(ctx, params.input_suffix, false, true);
-                    LOG("input tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, line_inp));
+                    LOG("input tokens: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx, line_inp).c_str());
 
                     embd_inp.insert(embd_inp.end(), line_pfx.begin(), line_pfx.end());
                     embd_inp.insert(embd_inp.end(), line_inp.begin(), line_inp.end());
@@ -830,15 +800,7 @@ int main(int argc, char ** argv) {
 
             if (n_past > 0) {
                 if (is_interacting) {
-                    // reset grammar state if we're restarting generation
-                    if (grammar != NULL) {
-                        llama_grammar_free(grammar);
-
-                        std::vector<const llama_grammar_element *> grammar_rules(parsed_grammar.c_rules());
-                        grammar = llama_grammar_init(
-                            grammar_rules.data(), grammar_rules.size(),
-                            parsed_grammar.symbol_ids.at("root"));
-                    }
+                    llama_sampling_reset(ctx_sampling);
                 }
                 is_interacting = false;
             }
@@ -870,9 +832,7 @@ int main(int argc, char ** argv) {
     llama_free(ctx);
     llama_free_model(model);
 
-    if (grammar != NULL) {
-        llama_grammar_free(grammar);
-    }
+    llama_sampling_free(ctx_sampling);
     llama_backend_free();
 
 #ifndef LOG_DISABLE_LOGS
diff --git a/examples/parallel/parallel.cpp b/examples/parallel/parallel.cpp
index 63ddcd8e..69f9526a 100644
--- a/examples/parallel/parallel.cpp
+++ b/examples/parallel/parallel.cpp
@@ -51,6 +51,12 @@ static std::vector<std::string> k_prompts = {
 };
 
 struct client {
+    ~client() {
+        if (ctx_sampling) {
+            llama_sampling_free(ctx_sampling);
+        }
+    }
+
     int32_t id = 0;
 
     llama_seq_id seq_id = -1;
@@ -68,7 +74,7 @@ struct client {
     std::string prompt;
     std::string response;
 
-    std::vector<llama_token> tokens_prev;
+    struct llama_sampling_context * ctx_sampling = nullptr;
 };
 
 static void print_date_time() {
@@ -125,8 +131,6 @@ int main(int argc, char ** argv) {
     params.logits_all = true;
     std::tie(model, ctx) = llama_init_from_gpt_params(params);
 
-    llama_sampling_context ctx_sampling = llama_sampling_context_init(params, NULL);
-
     // load the prompts from an external file if there are any
     if (params.prompt.empty()) {
         printf("\n\033[32mNo new questions so proceed with build-in defaults.\033[0m\n");
@@ -147,20 +151,15 @@ int main(int argc, char ** argv) {
     fprintf(stderr, "\n\n");
     fflush(stderr);
 
-    const int n_ctx   = llama_n_ctx(ctx);
-    const int n_vocab = llama_n_vocab(model);
+    const int n_ctx = llama_n_ctx(ctx);
 
     std::vector<client> clients(n_clients);
     for (size_t i = 0; i < clients.size(); ++i) {
         auto & client = clients[i];
         client.id = i;
-        client.tokens_prev.resize(std::max(256, params.n_predict));
-        std::fill(client.tokens_prev.begin(), client.tokens_prev.end(), 0);
+        client.ctx_sampling = llama_sampling_init(params);
     }
 
-    std::vector<llama_token_data> candidates;
-    candidates.reserve(n_vocab);
-
     std::vector<llama_token> tokens_system;
     tokens_system = ::llama_tokenize(ctx, k_system, true);
     const int32_t n_tokens_system = tokens_system.size();
@@ -169,7 +168,7 @@ int main(int argc, char ** argv) {
 
     // the max batch size is as large as the context to handle cases where we get very long input prompt from multiple
     // users. regardless of the size, the main loop will chunk the batch into a maximum of params.n_batch tokens at a time
-    llama_batch batch = llama_batch_init(n_ctx, 0);
+    llama_batch batch = llama_batch_init(n_ctx, 0, 1);
 
     int32_t n_total_prompt = 0;
     int32_t n_total_gen    = 0;
@@ -184,13 +183,8 @@ int main(int argc, char ** argv) {
     {
         LOG_TEE("%s: Evaluating the system prompt ...\n", __func__);
 
-        batch.n_tokens = n_tokens_system;
-
-        for (int32_t i = 0; i < batch.n_tokens; ++i) {
-            batch.token[i]  = tokens_system[i];
-            batch.pos[i]    = i;
-            batch.seq_id[i] = 0;
-            batch.logits[i] = false;
+        for (int32_t i = 0; i < n_tokens_system; ++i) {
+            llama_batch_add(batch, tokens_system[i], i, { 0 }, false);
         }
 
         if (llama_decode(ctx, batch) != 0) {
@@ -209,7 +203,7 @@ int main(int argc, char ** argv) {
     LOG_TEE("Processing requests ...\n\n");
 
     while (true) {
-        batch.n_tokens = 0;
+        llama_batch_clear(batch);
 
         // decode any currently ongoing sequences
         for (auto & client : clients) {
@@ -217,15 +211,11 @@ int main(int argc, char ** argv) {
                 continue;
             }
 
-            batch.token [batch.n_tokens] = client.sampled;
-            batch.pos   [batch.n_tokens] = n_tokens_system + client.n_prompt + client.n_decoded;
-            batch.seq_id[batch.n_tokens] = client.id;
-            batch.logits[batch.n_tokens] = true;
-
-            client.n_decoded += 1;
             client.i_batch = batch.n_tokens;
 
-            batch.n_tokens += 1;
+            llama_batch_add(batch, client.sampled, n_tokens_system + client.n_prompt + client.n_decoded, { client.id }, true);
+
+            client.n_decoded += 1;
         }
 
         if (batch.n_tokens == 0) {
@@ -250,18 +240,14 @@ int main(int argc, char ** argv) {
                     client.prompt   = client.input + "\nAssistant:";
                     client.response = "";
 
-                    std::fill(client.tokens_prev.begin(), client.tokens_prev.end(), 0);
+                    llama_sampling_reset(client.ctx_sampling);
 
                     // do not prepend BOS because we have a system prompt!
                     std::vector<llama_token> tokens_prompt;
                     tokens_prompt = ::llama_tokenize(ctx, client.prompt, false);
 
                     for (size_t i = 0; i < tokens_prompt.size(); ++i) {
-                        batch.token [batch.n_tokens] = tokens_prompt[i];
-                        batch.pos   [batch.n_tokens] = i + n_tokens_system;
-                        batch.seq_id[batch.n_tokens] = client.id;
-                        batch.logits[batch.n_tokens] = false;
-                        batch.n_tokens += 1;
+                        llama_batch_add(batch, tokens_prompt[i], i + n_tokens_system, { client.id }, false);
                     }
 
                     // extract the logits only for the last token
@@ -304,11 +290,12 @@ int main(int argc, char ** argv) {
 
             llama_batch batch_view = {
                 n_tokens,
-                batch.token  + i,
+                batch.token    + i,
                 nullptr,
-                batch.pos    + i,
-                batch.seq_id + i,
-                batch.logits + i,
+                batch.pos      + i,
+                batch.n_seq_id + i,
+                batch.seq_id   + i,
+                batch.logits   + i,
                 0, 0, 0, // unused
             };
 
@@ -341,7 +328,9 @@ int main(int argc, char ** argv) {
                 //printf("client %d, seq %d, token %d, pos %d, batch %d\n",
                 //        client.id, client.seq_id, client.sampled, client.n_decoded, client.i_batch);
 
-                const llama_token id = llama_sampling_sample(ctx, NULL, ctx_sampling, client.tokens_prev, candidates, client.i_batch - i, client.seq_id);
+                const llama_token id = llama_sampling_sample(client.ctx_sampling, ctx, NULL, client.i_batch - i);
+
+                llama_sampling_accept(client.ctx_sampling, ctx, id);
 
                 if (client.n_decoded == 1) {
                     // start measuring generation time after the first token to make sure all concurrent clients
@@ -349,11 +338,8 @@ int main(int argc, char ** argv) {
                     client.t_start_gen = ggml_time_us();
                 }
 
-                // remember which tokens were sampled - used for repetition penalties during sampling
-                client.tokens_prev.erase(client.tokens_prev.begin());
-                client.tokens_prev.push_back(id);
-
                 const std::string token_str = llama_token_to_piece(ctx, id);
+
                 client.response += token_str;
                 client.sampled = id;
 
@@ -386,7 +372,7 @@ int main(int argc, char ** argv) {
 
                     n_total_prompt += client.n_prompt;
                     n_total_gen    += client.n_decoded;
-                    llama_sampling_context_reset(ctx_sampling, client.seq_id);
+
                     client.seq_id = -1;
                 }
 
diff --git a/examples/server/server.cpp b/examples/server/server.cpp
index ee0ababb..28b3f3f5 100644
--- a/examples/server/server.cpp
+++ b/examples/server/server.cpp
@@ -1,7 +1,6 @@
 #include "common.h"
 #include "llama.h"
 #include "build-info.h"
-#include "grammar-parser.h"
 
 #ifndef NDEBUG
 // crash the server in debug mode, otherwise send an http 500 error
@@ -195,17 +194,13 @@ struct llama_server_context
 
     json prompt;
     std::vector<llama_token> embd;
-    std::vector<llama_token> last_n_tokens;
 
     llama_model *model = nullptr;
     llama_context *ctx = nullptr;
     gpt_params params;
-    llama_sampling_context ctx_sampling;
+    llama_sampling_context *ctx_sampling;
     int n_ctx;
 
-    grammar_parser::parse_state parsed_grammar;
-    llama_grammar *grammar = nullptr;
-
     bool truncated = false;
     bool stopped_eos = false;
     bool stopped_word = false;
@@ -252,11 +247,10 @@ struct llama_server_context
         n_remain = 0;
         n_past = 0;
 
-        if (grammar != nullptr) {
-            llama_grammar_free(grammar);
-            grammar = nullptr;
-            ctx_sampling = llama_sampling_context_init(params, NULL);
+        if (ctx_sampling != nullptr) {
+            llama_sampling_free(ctx_sampling);
         }
+        ctx_sampling = llama_sampling_init(params);
     }
 
     bool loadModel(const gpt_params &params_)
@@ -269,8 +263,6 @@ struct llama_server_context
             return false;
         }
         n_ctx = llama_n_ctx(ctx);
-        last_n_tokens.resize(n_ctx);
-        std::fill(last_n_tokens.begin(), last_n_tokens.end(), 0);
         return true;
     }
 
@@ -321,27 +313,7 @@ struct llama_server_context
 
     bool loadGrammar()
     {
-        if (!params.grammar.empty()) {
-            parsed_grammar = grammar_parser::parse(params.grammar.c_str());
-            // will be empty (default) if there are parse errors
-            if (parsed_grammar.rules.empty()) {
-                LOG_ERROR("grammar parse error", {{"grammar", params.grammar}});
-                return false;
-            }
-            grammar_parser::print_grammar(stderr, parsed_grammar);
-
-            {
-                auto it = params.sampling_params.logit_bias.find(llama_token_eos(ctx));
-                if (it != params.sampling_params.logit_bias.end() && it->second == -INFINITY) {
-                    LOG_WARNING("EOS token is disabled, which will cause most grammars to fail", {});
-                }
-            }
-
-            std::vector<const llama_grammar_element *> grammar_rules(parsed_grammar.c_rules());
-            grammar = llama_grammar_init(
-                grammar_rules.data(), grammar_rules.size(), parsed_grammar.symbol_ids.at("root"));
-        }
-        ctx_sampling = llama_sampling_context_init(params, grammar);
+        ctx_sampling = llama_sampling_init(params);
         return true;
     }
 
@@ -383,7 +355,7 @@ struct llama_server_context
             std::vector<llama_token> new_tokens(prompt_tokens.begin(), prompt_tokens.begin() + params.n_keep);
             const int erased_blocks = (num_prompt_tokens - params.n_keep - n_left - 1) / n_left;
             new_tokens.insert(new_tokens.end(), prompt_tokens.begin() + params.n_keep + erased_blocks * n_left, prompt_tokens.end());
-            std::copy(prompt_tokens.end() - params.n_ctx, prompt_tokens.end(), last_n_tokens.begin());
+            std::copy(prompt_tokens.end() - params.n_ctx, prompt_tokens.end(), ctx_sampling->prev.begin());
 
             LOG_VERBOSE("input truncated", {
                                                {"n_ctx", params.n_ctx},
@@ -398,8 +370,8 @@ struct llama_server_context
         else
         {
             const size_t ps = num_prompt_tokens;
-            std::fill(last_n_tokens.begin(), last_n_tokens.end() - ps, 0);
-            std::copy(prompt_tokens.begin(), prompt_tokens.end(), last_n_tokens.end() - ps);
+            std::fill(ctx_sampling->prev.begin(), ctx_sampling->prev.end() - ps, 0);
+            std::copy(prompt_tokens.begin(), prompt_tokens.end(), ctx_sampling->prev.end() - ps);
         }
 
         // compare the evaluated prompt with the new prompt
@@ -443,7 +415,7 @@ struct llama_server_context
             std::vector<llama_token> new_tokens(prompt_tokens.begin(), prompt_tokens.begin() + params.n_keep);
             const int erased_blocks = (num_prompt_tokens - params.n_keep - n_left - 1) / n_left;
             new_tokens.insert(new_tokens.end(), prompt_tokens.begin() + params.n_keep + erased_blocks * n_left, prompt_tokens.end());
-            std::copy(prompt_tokens.end() - n_ctx, prompt_tokens.end(), last_n_tokens.begin());
+            std::copy(prompt_tokens.end() - n_ctx, prompt_tokens.end(), ctx_sampling->prev.begin());
 
             LOG_VERBOSE("input truncated", {
                                                {"n_ctx", n_ctx},
@@ -458,8 +430,8 @@ struct llama_server_context
         else
         {
             const size_t ps = num_prompt_tokens;
-            std::fill(last_n_tokens.begin(), last_n_tokens.end() - ps, 0);
-            std::copy(prompt_tokens.begin(), prompt_tokens.end(), last_n_tokens.end() - ps);
+            std::fill(ctx_sampling->prev.begin(), ctx_sampling->prev.end() - ps, 0);
+            std::copy(prompt_tokens.begin(), prompt_tokens.end(), ctx_sampling->prev.end() - ps);
         }
 
         // compare the evaluated prompt with the new prompt
@@ -554,27 +526,24 @@ struct llama_server_context
 
         {
             // out of user input, sample next token
-            std::vector<llama_token_data> candidates;
-            candidates.reserve(llama_n_vocab(model));
-
-            result.tok = llama_sampling_sample(ctx, NULL, ctx_sampling, last_n_tokens, candidates);
+            result.tok = llama_sampling_sample(ctx_sampling, ctx, NULL);
 
-            llama_token_data_array candidates_p = { candidates.data(), candidates.size(), false };
+            llama_token_data_array cur_p = { ctx_sampling->cur.data(), ctx_sampling->cur.size(), false };
 
             const int32_t n_probs = params.sampling_params.n_probs;
             if (params.sampling_params.temp <= 0 && n_probs > 0)
             {
                 // For llama_sample_token_greedy we need to sort candidates
-                llama_sample_softmax(ctx, &candidates_p);
+                llama_sample_softmax(ctx, &cur_p);
             }
 
-            for (size_t i = 0; i < std::min(candidates_p.size, (size_t)n_probs); ++i)
+            for (size_t i = 0; i < std::min(cur_p.size, (size_t)n_probs); ++i)
             {
-                result.probs.push_back({candidates_p.data[i].id, candidates_p.data[i].p});
+                result.probs.push_back({cur_p.data[i].id, cur_p.data[i].p});
             }
 
-            last_n_tokens.erase(last_n_tokens.begin());
-            last_n_tokens.push_back(result.tok);
+            llama_sampling_accept(ctx_sampling, ctx, result.tok);
+
             if (tg) {
                 num_tokens_predicted++;
             }
@@ -1235,7 +1204,7 @@ static void parse_options_completion(const json &body, llama_server_context &lla
         }
     }
 
-    llama.ctx_sampling = llama_sampling_context_init(llama.params, llama.grammar);
+    llama.ctx_sampling = llama_sampling_init(llama.params);
 
     LOG_VERBOSE("completion parameters parsed", format_generation_settings(llama));
 }
@@ -1793,9 +1762,7 @@ int main(int argc, char **argv)
         return 1;
     }
 
-    if (llama.grammar != nullptr) {
-        llama_grammar_free(llama.grammar);
-    }
+    llama_sampling_free(llama.ctx_sampling);
     llama_backend_free();
 
     return 0;
diff --git a/examples/simple/simple.cpp b/examples/simple/simple.cpp
index 24fb16b7..55385f56 100644
--- a/examples/simple/simple.cpp
+++ b/examples/simple/simple.cpp
@@ -92,7 +92,7 @@ int main(int argc, char ** argv) {
     // create a llama_batch with size 512
     // we use this object to submit token data for decoding
 
-    llama_batch batch = llama_batch_init(512, 0);
+    llama_batch batch = llama_batch_init(512, 0, 1);
 
     // evaluate the initial prompt
     batch.n_tokens = tokens_list.size();
diff --git a/examples/speculative/speculative.cpp b/examples/speculative/speculative.cpp
index 018dbf9a..53f42fad 100644
--- a/examples/speculative/speculative.cpp
+++ b/examples/speculative/speculative.cpp
@@ -2,13 +2,25 @@
 
 #include "common.h"
 #include "llama.h"
-#include "grammar-parser.h"
 
 #include <cmath>
 #include <cstdio>
 #include <string>
 #include <vector>
 
+struct seq_draft {
+    bool active   = false;
+    bool drafting = false;
+    bool skip     = false;
+
+    int i_batch_dft = 0;
+    std::vector<int> i_batch_tgt;
+
+    std::vector<llama_token> tokens;
+
+    struct llama_sampling_context * ctx_sampling;
+};
+
 int main(int argc, char ** argv) {
     gpt_params params;
 
@@ -21,6 +33,13 @@ int main(int argc, char ** argv) {
         return 1;
     }
 
+    // max number of parallel drafting sequences (i.e. tree branches)
+    const int n_seq_dft = params.n_parallel;
+
+    // TODO: make this configurable
+    const float p_accept = 0.4f;
+    const float p_split  = 0.3f;
+
 #ifndef LOG_DISABLE_LOGS
     log_set_target(log_filename_generator("speculative", "log"));
     LOG_TEE("Log start\n");
@@ -77,8 +96,6 @@ int main(int argc, char ** argv) {
     const auto t_enc_end = ggml_time_us();
 
     // the 2 models should have the same vocab
-    const int n_ctx   = llama_n_ctx(ctx_tgt);
-    const int n_vocab = llama_n_vocab(model_tgt);
     //GGML_ASSERT(n_vocab == llama_n_vocab(model_dft));
 
     // how many tokens to draft each time
@@ -91,60 +108,58 @@ int main(int argc, char ** argv) {
     int n_past_tgt = inp.size();
     int n_past_dft = inp.size();
 
-    std::vector<llama_token> drafted;
-
-    std::vector<llama_token> last_tokens(n_ctx);
-    std::fill(last_tokens.begin(), last_tokens.end(), 0);
-
-    for (auto & id : inp) {
-        last_tokens.erase(last_tokens.begin());
-        last_tokens.push_back(id);
-    }
-
-    std::vector<llama_token_data> candidates;
-    candidates.reserve(n_vocab);
-
     // used to determine end of generation
     bool has_eos = false;
 
-    // grammar stuff
-    struct llama_grammar * grammar_dft = NULL;
-    struct llama_grammar * grammar_tgt = NULL;
+    // target model sampling context
+    struct llama_sampling_context * ctx_sampling = llama_sampling_init(params);
 
-    grammar_parser::parse_state parsed_grammar;
+    // draft sequence data
+    std::vector<seq_draft> drafts(n_seq_dft);
 
-    // if requested - load the grammar, error checking is omitted for brevity
-    if (!params.grammar.empty()) {
-        parsed_grammar = grammar_parser::parse(params.grammar.c_str());
-        // will be empty (default) if there are parse errors
-        if (parsed_grammar.rules.empty()) {
-            return 1;
-        }
+    params.grammar.clear();             // the draft samplers will copy the target sampler's grammar
+    params.sampling_params.temp = 1.0f; // the draft samplers use default temperature
 
-        std::vector<const llama_grammar_element *> grammar_rules(parsed_grammar.c_rules());
-        grammar_tgt = llama_grammar_init(grammar_rules.data(), grammar_rules.size(), parsed_grammar.symbol_ids.at("root"));
+    for (int s = 0; s < n_seq_dft; ++s) {
+        drafts[s].ctx_sampling = llama_sampling_init(params);
     }
 
-    llama_sampling_context ctx_sampling = llama_sampling_context_init(params, grammar_tgt);
+    llama_batch batch_dft = llama_batch_init(params.n_ctx, 0, 1);
+    llama_batch batch_tgt = llama_batch_init(params.n_ctx, 0, n_seq_dft);
 
     const auto t_dec_start = ggml_time_us();
 
+    // sample from the last token of the prompt
+    drafts[0].i_batch_tgt.resize(1);
+    drafts[0].i_batch_tgt[0] = 0;
+
     while (true) {
-        LOG("drafted: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_dft, drafted));
+        // print current draft sequences
+        for (int s = 0; s < n_seq_dft; ++s) {
+            if (!drafts[s].active) {
+                continue;
+            }
+
+            const auto & tokens = drafts[s].tokens;
 
-        int i_dft = 0;
+            LOG("draft %d: %s\n", s, LOG_TOKENS_TOSTR_PRETTY(ctx_dft, tokens).c_str());
+        }
+
+        int i_dft  = 0;
+        int s_keep = 0;
 
         while (true) {
+            LOG("sampling target: s_keep = %3d, i_dft = %3d, i_batch_tgt = %3d\n", s_keep, i_dft, drafts[s_keep].i_batch_tgt[i_dft]);
+
             // sample from the target model
-            llama_token id = llama_sampling_sample(ctx_tgt, NULL, ctx_sampling, last_tokens, candidates, i_dft);
+            llama_token id = llama_sampling_sample(ctx_sampling, ctx_tgt, NULL, drafts[s_keep].i_batch_tgt[i_dft]);
 
-            // remember which tokens were sampled - used for repetition penalties during sampling
-            last_tokens.erase(last_tokens.begin());
-            last_tokens.push_back(id);
+            llama_sampling_accept(ctx_sampling, ctx_tgt, id);
 
             //LOG("last: %s\n", LOG_TOKENS_TOSTR_PRETTY(ctx_tgt, last_tokens));
 
             const std::string token_str = llama_token_to_piece(ctx_tgt, id);
+
             printf("%s", token_str.c_str());
             fflush(stdout);
 
@@ -154,53 +169,67 @@ int main(int argc, char ** argv) {
 
             ++n_predict;
 
-            // check if the draft matches the target
-            if (i_dft < (int) drafted.size() && id == drafted[i_dft]) {
-                LOG("the sampled target token matches the %dth drafted token (%d, '%s') - accepted\n", i_dft, id, token_str.c_str());
-                ++n_accept;
-                ++n_past_tgt;
-                ++n_past_dft;
-                ++i_dft;
+            // check if the target token matches any of the drafts
+            {
+                bool matches = false;
 
-                continue;
-            }
+                for (int s = 0; s < n_seq_dft; ++s) {
+                    if (!drafts[s].active) {
+                        continue;
+                    }
+
+                    if (i_dft < (int) drafts[s].tokens.size() && id == drafts[s].tokens[i_dft]) {
+                        LOG("the sampled target token matches the %dth drafted token of sequence %d (%d, '%s') - accepted\n", i_dft, s, id, token_str.c_str());
+
+                        s_keep = s;
+                        matches = true;
+                    } else {
+                        drafts[s].active = false;
+                    }
+                }
 
-            // the drafted token was rejected or we are out of drafted tokens
+                if (matches) {
+                    ++n_accept;
+                    ++n_past_tgt;
+                    ++n_past_dft;
+                    ++i_dft;
 
-            if (i_dft < (int) drafted.size()) {
-                LOG("the %dth drafted token (%d, '%s') does not match the sampled target token (%d, '%s') - rejected\n",
-                        i_dft, drafted[i_dft], llama_token_to_piece(ctx_dft, drafted[i_dft]).c_str(), id, token_str.c_str());
-            } else {
-                LOG("out of drafted tokens\n");
+                    continue;
+                }
             }
 
-            llama_kv_cache_seq_rm(ctx_dft, 0, n_past_dft, -1);
-            llama_decode(ctx_dft, llama_batch_get_one(&id, 1, n_past_dft, 0));
-            ++n_past_dft;
+            LOG("the sampled target token (%d, '%s') did not match, or we ran out of drafted tokens\n", id, token_str.c_str());
 
-            // heuristic for n_draft
+            // TODO: simplify
             {
-                const int  n_draft_cur  = (int) drafted.size();
-                const bool all_accepted = i_dft == n_draft_cur;
-
-                LOG("n_draft      = %d\n", n_draft);
-                LOG("n_draft_cur  = %d\n", n_draft_cur);
-                LOG("i_dft        = %d\n", i_dft);
-                LOG("all_accepted = %d\n", all_accepted);
-
-                if (all_accepted && n_draft == n_draft_cur) {
-                    LOG(" - max drafted tokens accepted - n_draft += 8\n");
-                    n_draft = std::min(30, n_draft + 8);
-                } else if (all_accepted) {
-                    LOG(" - partially drafted tokens accepted - no change\n");
-                } else {
-                    LOG(" - drafted token rejected - n_draft -= 1\n");
-                    n_draft = std::max(2, n_draft - 1);
-                }
+                LOG("keeping sequence %d\n", s_keep);
+
+                llama_kv_cache_seq_keep(ctx_dft, s_keep);
+                llama_kv_cache_seq_cp  (ctx_dft, s_keep, 0, -1, -1);
+                llama_kv_cache_seq_keep(ctx_dft, 0);
+
+                llama_kv_cache_seq_rm  (ctx_tgt, s_keep, n_past_tgt, -1);
+                llama_kv_cache_seq_keep(ctx_tgt, s_keep);
+                llama_kv_cache_seq_cp  (ctx_tgt, s_keep, 0, -1, -1);
+                llama_kv_cache_seq_keep(ctx_tgt, 0);
             }
 
-            drafted.clear();
-            drafted.push_back(id);
+            for (int s = 0; s < n_seq_dft; ++s) {
+                drafts[s].active = false;
+                drafts[s].tokens.clear();
+                drafts[s].i_batch_tgt.clear();
+            }
+            // note: will be erased after the speculation phase
+            drafts[0].tokens.push_back(id);
+            drafts[0].i_batch_tgt.push_back(0);
+
+            llama_batch_clear(batch_dft);
+            llama_batch_add  (batch_dft, id, n_past_dft, { 0 }, true);
+
+            llama_kv_cache_seq_rm(ctx_dft, 0, n_past_dft, -1);
+            llama_decode         (ctx_dft, batch_dft);
+
+            ++n_past_dft;
 
             break;
         }
@@ -209,78 +238,158 @@ int main(int argc, char ** argv) {
             break;
         }
 
-        if (grammar_tgt) {
-            if (grammar_dft) {
-                llama_grammar_free(grammar_dft);
-            }
-            // Note: Hardcoded to sequence id 0, if this ever supports parallel generation
-            //       that will need to change.
-            auto it = ctx_sampling.sequence_contexts.find(0);
-            GGML_ASSERT(it != ctx_sampling.sequence_contexts.end());
-            // This is necessary because each sequence id in sequence_contexts
-            // uses a copy of the original grammar.
-            grammar_dft = llama_grammar_copy(it->second.grammar);
-
-            LOG("copied target grammar to draft grammar\n");
-        }
+        llama_sampling_cp(ctx_sampling, drafts[0].ctx_sampling);
 
-        // sample n_draft tokens from the draft model using greedy decoding
+        int n_seq_cur  = 1;
         int n_past_cur = n_past_dft;
+
+        for (int s = 0; s < n_seq_dft; ++s) {
+            drafts[s].active   = false;
+            drafts[s].drafting = false;
+        }
+        drafts[0].active      = true;
+        drafts[0].drafting    = true;
+        drafts[0].i_batch_dft = 0;
+
+        llama_batch_clear(batch_tgt);
+        llama_batch_add  (batch_tgt, drafts[0].tokens[0], n_past_tgt, { 0 }, true);
+
+        // sample n_draft tokens from the draft model using tree-based sampling
         for (int i = 0; i < n_draft; ++i) {
-            float * logits = llama_get_logits(ctx_dft);
+            batch_dft.n_tokens = 0;
 
-            candidates.clear();
-            for (llama_token token_id = 0; token_id < n_vocab; token_id++) {
-                candidates.emplace_back(llama_token_data{token_id, logits[token_id], 0.0f});
+            for (int s = 0; s < n_seq_dft; ++s) {
+                drafts[s].skip = false;
             }
 
-            llama_token_data_array cur_p = { candidates.data(), candidates.size(), false };
+            for (int s = 0; s < n_seq_dft; ++s) {
+                if (!drafts[s].drafting || drafts[s].skip) {
+                    continue;
+                }
 
-            if (grammar_dft != NULL) {
-                llama_sample_grammar(ctx_dft, &cur_p, grammar_dft);
-            }
+                llama_sampling_sample(drafts[s].ctx_sampling, ctx_dft, NULL, drafts[s].i_batch_dft);
+
+                const auto & cur_p = drafts[s].ctx_sampling->cur;
+
+                for (int k = 0; k < std::min(n_seq_dft + 3, (int) cur_p.size()); ++k) {
+                    LOG(" - draft candidate %3d for seq %3d, pos %3d: %6d (%8.3f) '%s'\n",
+                            k, s, i, cur_p[k].id, cur_p[k].p, llama_token_to_piece(ctx_dft, cur_p[k].id).c_str());
+                }
+
+                if (cur_p[0].p < p_accept) {
+                    LOG("stopping drafting for seq %3d, probability too low: %.3f < 2*%.3f\n", s, cur_p[0].p, cur_p[1].p);
+                    drafts[s].drafting = false;
+                    continue;
+                }
+
+                std::vector<int> sa(1, s);
+
+                // attempt to split the branch if the probability is high enough
+                for (int f = 1; f < 8; ++f) {
+                    if (n_seq_cur < n_seq_dft && cur_p[f].p > p_split) {
+                        LOG("splitting seq %3d into %3d\n", s, n_seq_cur);
+
+                        llama_kv_cache_seq_rm(ctx_dft,    n_seq_cur, -1, -1);
+                        llama_kv_cache_seq_cp(ctx_dft, s, n_seq_cur, -1, -1);
+
+                        // all previous tokens from this branch are now also part of the new branch
+                        for (int t = 0; t < batch_tgt.n_tokens; ++t) {
+                            for (int p = 0; p < batch_tgt.n_seq_id[t]; ++p) {
+                                if (batch_tgt.seq_id[t][p] == s) {
+                                    batch_tgt.seq_id[t][batch_tgt.n_seq_id[t]] = n_seq_cur;
+                                    batch_tgt.n_seq_id[t]++;
+                                    break;
+                                }
+                            }
+                        }
+
+                        // copy the draft state
+                        drafts[n_seq_cur].active   = true;
+                        drafts[n_seq_cur].drafting = true;
+                        drafts[n_seq_cur].skip     = true;
+
+                        drafts[n_seq_cur].tokens      = drafts[s].tokens;
+                        drafts[n_seq_cur].i_batch_dft = drafts[s].i_batch_dft;
+                        drafts[n_seq_cur].i_batch_tgt = drafts[s].i_batch_tgt;
+
+                        llama_sampling_cp(drafts[s].ctx_sampling, drafts[n_seq_cur].ctx_sampling);
+
+                        sa.push_back(n_seq_cur);
+
+                        n_seq_cur++;
+                    } else {
+                        break;
+                    }
+                }
+
+                // add drafted token for each sequence
+                for (int is = 0; is < (int) sa.size(); ++is) {
+                    const llama_token id = cur_p[is].id;
+
+                    const int s = sa[is];
+
+                    llama_sampling_accept(drafts[s].ctx_sampling, ctx_dft, id);
 
-            // computes softmax and sorts the candidates
-            llama_sample_softmax(ctx_dft, &cur_p);
+                    drafts[s].tokens.push_back(id);
 
-            for (int i = 0; i < 3; ++i) {
-                LOG(" - draft candidate %3d: %6d (%8.3f) '%s'\n", i, cur_p.data[i].id, cur_p.data[i].p, llama_token_to_piece(ctx_dft, cur_p.data[i].id).c_str());
+                    // add unique drafted tokens to the target batch
+                    drafts[s].i_batch_tgt.push_back(batch_tgt.n_tokens);
+
+                    llama_batch_add(batch_tgt, id, n_past_tgt + i + 1, { s }, true);
+
+                    // no need to evaluate the last drafted token, since we won't use the result
+                    if (batch_tgt.n_tokens > n_draft) {
+                        drafts[s].drafting = false;
+                        continue;
+                    }
+
+                    // add the token to the batch for batched decoding with the draft model
+                    drafts[s].i_batch_dft = batch_dft.n_tokens;
+
+                    llama_batch_add(batch_dft, id, n_past_cur, { s }, true);
+                }
             }
 
-            // TODO: better logic?
-            if (cur_p.data[0].p < 2*cur_p.data[1].p) {
-                LOG("stopping drafting, probability too low: %.3f < 2*%.3f\n", cur_p.data[0].p, cur_p.data[1].p);
+            // no sequence is drafting anymore
+            if (batch_dft.n_tokens == 0) {
                 break;
             }
 
-            // drafted token
-            const llama_token id = cur_p.data[0].id;
-
-            drafted.push_back(id);
+            // evaluate the drafted tokens on the draft model
+            llama_decode(ctx_dft, batch_dft);
+            ++n_past_cur;
             ++n_drafted;
 
-            // no need to evaluate the last drafted token, since we won't use the result
-            if (i == n_draft - 1) {
+            if (batch_tgt.n_tokens > n_draft) {
                 break;
             }
+        }
 
-            // evaluate the drafted token on the draft model
-            llama_kv_cache_seq_rm(ctx_dft, 0, n_past_cur, -1);
-            llama_decode(ctx_dft, llama_batch_get_one(&drafted.back(), 1, n_past_cur, 0));
-            ++n_past_cur;
+        // account for the last drafted token that we didn't evaluate
+        if (batch_tgt.n_tokens > n_draft) {
+            ++n_drafted;
+        }
 
-            if (grammar_dft != NULL) {
-                llama_grammar_accept_token(ctx_dft, grammar_dft, id);
+        // evaluate the target model on the drafted tokens
+        {
+            llama_kv_cache_seq_keep(ctx_tgt, 0);
+            for (int s = 1; s < n_seq_dft; ++s) {
+                llama_kv_cache_seq_cp(ctx_tgt, 0, s, -1, -1);
             }
+
+            //LOG("target batch: %s\n", LOG_BATCH_TOSTR_PRETTY(ctx_tgt, batch_tgt));
+            llama_decode(ctx_tgt, batch_tgt);
+            ++n_past_tgt;
         }
 
-        // evaluate the target model on the drafted tokens
-        llama_kv_cache_seq_rm(ctx_tgt, 0, n_past_tgt, -1);
-        llama_decode(ctx_tgt, llama_batch_get_one(drafted.data(), drafted.size(), n_past_tgt, 0));
-        ++n_past_tgt;
+        // the first token is always proposed by the traget model before the speculation loop so we erase it here
+        for (int s = 0; s < n_seq_dft; ++s) {
+            if (!drafts[s].active) {
+                continue;
+            }
 
-        // the first token is always proposed by the traget model before the speculation loop
-        drafted.erase(drafted.begin());
+            drafts[s].tokens.erase(drafts[s].tokens.begin());
+        }
     }
 
     auto t_dec_end = ggml_time_us();
@@ -288,9 +397,8 @@ int main(int argc, char ** argv) {
     LOG_TEE("\n\n");
 
     LOG_TEE("encoded %4d tokens in %8.3f seconds, speed: %8.3f t/s\n", n_input,   (t_enc_end - t_enc_start) / 1e6f, inp.size() / ((t_enc_end - t_enc_start) / 1e6f));
-    LOG_TEE("decoded %4d tokens in %8.3f seconds, speed: %8.3f t/s\n", n_predict, (t_dec_end - t_dec_start) / 1e6f, n_predict / ((t_dec_end - t_dec_start) / 1e6f));
+    LOG_TEE("decoded %4d tokens in %8.3f seconds, speed: %8.3f t/s\n", n_predict, (t_dec_end - t_dec_start) / 1e6f, n_predict  / ((t_dec_end - t_dec_start) / 1e6f));
 
-    // TODO: make sure these numbers are computed correctly
     LOG_TEE("\n");
     LOG_TEE("n_draft   = %d\n", n_draft);
     LOG_TEE("n_predict = %d\n", n_predict);
@@ -304,16 +412,19 @@ int main(int argc, char ** argv) {
     LOG_TEE("\ntarget:\n");
     llama_print_timings(ctx_tgt);
 
+    llama_sampling_free(ctx_sampling);
+    for (int s = 0; s < n_seq_dft; ++s) {
+        llama_sampling_free(drafts[s].ctx_sampling);
+    }
+
+    llama_batch_free(batch_dft);
+
     llama_free(ctx_tgt);
     llama_free_model(model_tgt);
 
     llama_free(ctx_dft);
     llama_free_model(model_dft);
 
-    if (grammar_dft != NULL) {
-        llama_grammar_free(grammar_dft);
-        llama_grammar_free(grammar_tgt);
-    }
     llama_backend_free();
 
     fprintf(stderr, "\n\n");