Adding top-n-sigma sampler (#489)

* Adding top-n-sigma sampler

* Fix typos in XTC PR

* Update README.md for main and server

* More README

* More README

---------

Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>

3 files changed, 25 insertions, 10 deletions

diff --git a/common/common.cpp b/common/common.cpp
index cefbf63f..232101e4 100644
--- a/common/common.cpp
+++ b/common/common.cpp
@@ -659,6 +659,11 @@ bool gpt_params_find_arg(int argc, char ** argv, const std::string & arg, gpt_pa
         sparams.xtc_threshold = std::stof(argv[i]);
         return true;
     }
+    if (arg == "--top-n-sigma") {
+        CHECK_ARG
+        sparams.top_n_sigma = std::stof(argv[i]);
+        return true;
+    }
     if (arg == "--cfg-negative-prompt") {
         CHECK_ARG
         sparams.cfg_negative_prompt = argv[i];
@@ -1646,7 +1651,8 @@ void gpt_params_print_usage(int /*argc*/, char ** argv, const gpt_params & param
     options.push_back({ "*",           "       --mirostat-lr N",        "Mirostat learning rate, parameter eta (default: %.1f)", (double)sparams.mirostat_eta });
     options.push_back({ "*",           "       --mirostat-ent N",       "Mirostat target entropy, parameter tau (default: %.1f)", (double)sparams.mirostat_tau });
     options.push_back({ "*",           "       --xtc-probability p",    "xtc probability (default: %.1f, 0.0 = disabled)", (double)sparams.xtc_probability });
-    options.push_back({ "*",           "       --xtc-threshold t",      "xtc threshold (default: %.1f, 0.0 = disabled)", (double)sparams.xtc_threshold});
+    options.push_back({ "*",           "       --xtc-threshold t",      "xtc threshold (default: %.1f, >0.5 = disabled)", (double)sparams.xtc_threshold});
+    options.push_back({ "*",           "       --top-n-sigma t",        "top-n-sigma parmeter (default: %.1f, 0.0 = disabled)", (double)sparams.top_n_sigma});
     options.push_back({ "*",           "       -l TOKEN_ID(+/-)BIAS",   "modifies the likelihood of token appearing in the completion,\n"
                                                                         "i.e. `--logit-bias 15043+1` to increase likelihood of token ' Hello',\n"
                                                                         "or `--logit-bias 15043-1` to decrease likelihood of token ' Hello'" });
@@ -3410,6 +3416,7 @@ void yaml_dump_non_result_info(FILE * stream, const gpt_params & params, const l
     fprintf(stream, "mirostat_lr: %f # default: 0.1\n", sparams.mirostat_eta);
     fprintf(stream, "xtc_probability: %f # default: 0.0\n", sparams.xtc_probability);
     fprintf(stream, "xtc_threshold: %f # default: 0.0\n", sparams.xtc_threshold);
+    fprintf(stream, "top_n_sigma: %f # default: 0.0\n", sparams.top_n_sigma);
     fprintf(stream, "mlock: %s # default: false\n", params.use_mlock ? "true" : "false");
     fprintf(stream, "model: %s # default: %s\n", params.model.c_str(), DEFAULT_MODEL_PATH);
     fprintf(stream, "model_draft: %s # default:\n", params.model_draft.c_str());
diff --git a/common/sampling.cpp b/common/sampling.cpp
index 84691d93..4db12ee1 100644
--- a/common/sampling.cpp
+++ b/common/sampling.cpp
@@ -122,11 +122,11 @@ std::string llama_sampling_print(const llama_sampling_params & params) {
             "\trepeat_last_n = %d, repeat_penalty = %.3f, frequency_penalty = %.3f, presence_penalty = %.3f\n"
             "\ttop_k = %d, tfs_z = %.3f, top_p = %.3f, min_p = %.3f, typical_p = %.3f, temp = %.3f\n"
             "\tmirostat = %d, mirostat_lr = %.3f, mirostat_ent = %.3f\n"
-            "\txtc_probability = %.3f, xtc_threshold = %.3f",
+            "\txtc_probability = %.3f, xtc_threshold = %.3f, top_n_sigma = %.3f",
             params.penalty_last_n, params.penalty_repeat, params.penalty_freq, params.penalty_present,
             params.top_k, params.tfs_z, params.top_p, params.min_p, params.typical_p, params.temp,
             params.mirostat, params.mirostat_eta, params.mirostat_tau,
-            params.xtc_probability, params.xtc_threshold);
+            params.xtc_probability, params.xtc_threshold, params.top_n_sigma);
 
     return std::string(result);
 }
@@ -156,6 +156,7 @@ std::string llama_sampling_type_to_str(llama_sampler_type sampler_type) {
         case llama_sampler_type::MIN_P:       return "min_p";
         case llama_sampler_type::TEMPERATURE: return "temperature";
         case llama_sampler_type::XTC        : return "xtc";
+        case llama_sampler_type::TOP_N_SIGMA: return "top_n_sigma";
         default : return "";
     }
 }
@@ -168,6 +169,7 @@ std::vector<llama_sampler_type> llama_sampling_types_from_names(const std::vecto
         {"min_p",       llama_sampler_type::MIN_P},
         {"tfs_z",       llama_sampler_type::TFS_Z},
         {"xtc",         llama_sampler_type::XTC},
+        {"top_n_sigma", llama_sampler_type::TOP_N_SIGMA},
         {"temperature", llama_sampler_type::TEMPERATURE}
     };
 
@@ -183,6 +185,7 @@ std::vector<llama_sampler_type> llama_sampling_types_from_names(const std::vecto
         {"tfs-z",       llama_sampler_type::TFS_Z},
         {"tfs",         llama_sampler_type::TFS_Z},
         {"xtc",         llama_sampler_type::XTC},
+        {"top-n-sigma", llama_sampler_type::TOP_N_SIGMA},
         {"temp",        llama_sampler_type::TEMPERATURE}
     };
 
@@ -218,6 +221,7 @@ std::vector<llama_sampler_type> llama_sampling_types_from_chars(const std::strin
         {'m', llama_sampler_type::MIN_P},
         {'f', llama_sampler_type::TFS_Z},
         {'x', llama_sampler_type::XTC},
+        {'n', llama_sampler_type::TOP_N_SIGMA},
         {'t', llama_sampler_type::TEMPERATURE}
     };
 
@@ -248,16 +252,18 @@ static void sampler_queue(
     const float         typical_p         = params.typical_p;
     const float         xtc_probability   = params.xtc_probability;
     const float         xtc_threshold     = params.xtc_threshold;
+    const float         top_n_sigma       = params.top_n_sigma;
     const std::vector<llama_sampler_type> & samplers_sequence = params.samplers_sequence;
 
     for (auto sampler_type : samplers_sequence) {
         switch (sampler_type) {
-            case llama_sampler_type::TOP_K    : llama_sample_top_k    (ctx_main, &cur_p, top_k,     min_keep); break;
-            case llama_sampler_type::TFS_Z    : llama_sample_tail_free(ctx_main, &cur_p, tfs_z,     min_keep); break;
-            case llama_sampler_type::TYPICAL_P: llama_sample_typical  (ctx_main, &cur_p, typical_p, min_keep); break;
-            case llama_sampler_type::TOP_P    : llama_sample_top_p    (ctx_main, &cur_p, top_p,     min_keep); break;
-            case llama_sampler_type::MIN_P    : llama_sample_min_p    (ctx_main, &cur_p, min_p,     min_keep); break;
-            case llama_sampler_type::XTC      : llama_sample_xtc      (ctx_main, &cur_p, xtc_probability, xtc_threshold, min_keep); break;
+            case llama_sampler_type::TOP_K      : llama_sample_top_k    (ctx_main, &cur_p, top_k,     min_keep); break;
+            case llama_sampler_type::TFS_Z      : llama_sample_tail_free(ctx_main, &cur_p, tfs_z,     min_keep); break;
+            case llama_sampler_type::TYPICAL_P  : llama_sample_typical  (ctx_main, &cur_p, typical_p, min_keep); break;
+            case llama_sampler_type::TOP_P      : llama_sample_top_p    (ctx_main, &cur_p, top_p,     min_keep); break;
+            case llama_sampler_type::MIN_P      : llama_sample_min_p    (ctx_main, &cur_p, min_p,     min_keep); break;
+            case llama_sampler_type::XTC        : llama_sample_xtc      (ctx_main, &cur_p, xtc_probability, xtc_threshold, min_keep); break;
+            case llama_sampler_type::TOP_N_SIGMA: llama_sample_top_n_sigma(ctx_main, &cur_p, top_n_sigma); break;
             case llama_sampler_type::TEMPERATURE:
                 if (dynatemp_range > 0) {
                     float dynatemp_min = std::max(0.0f, temp - dynatemp_range);
diff --git a/common/sampling.h b/common/sampling.h
index 163cdfca..99fb07ac 100644
--- a/common/sampling.h
+++ b/common/sampling.h
@@ -16,6 +16,7 @@ enum class llama_sampler_type : char {
     MIN_P       = 'm',
     TFS_Z       = 'f',
     XTC         = 'x',
+    TOP_N_SIGMA = 'n',
     TYPICAL_P   = 'y',
     TEMPERATURE = 't'
 };
@@ -41,7 +42,8 @@ typedef struct llama_sampling_params {
     float       mirostat_tau          = 5.00f;              // target entropy
     float       mirostat_eta          = 0.10f;              // learning rate
     float       xtc_probability       = 0.0f;               // xtc probability
-    float       xtc_threshold         = 1.0f;               // xtc threashold, disabled if > 0.5
+    float       xtc_threshold         = 1.0f;               // xtc threshold, disabled if > 0.5
+    float       top_n_sigma           = 0.0f;               // top-n-sigma
     bool        penalize_nl           = false;              // consider newlines as a repeatable token
     uint32_t    seed                  = LLAMA_DEFAULT_SEED; // the seed used to initialize llama_sampling_context