server : add token healing support

Author: mare5x

examples/server/README.md

@@ -266,6 +266,8 @@ node index.js
 
     `json_schema`: Set a JSON schema for grammar-based sampling (e.g. `{"items": {"type": "string"}, "minItems": 10, "maxItems": 100}` of a list of strings, or `{}` for any JSON). See [tests](../../tests/test-json-schema-to-grammar.cpp) for supported features.  Default: no JSON schema.
 
+    `token_healing`: Set token healing strategy. Default: `0`, which is disabled.
+
     `seed`: Set the random number generator (RNG) seed.  Default: `-1`, which is a random seed.
 
     `ignore_eos`: Ignore end of stream token and continue generating.  Default: `false`

examples/server/server.cpp

@@ -184,6 +184,7 @@ struct server_slot {
     // stats
     size_t n_sent_text = 0; // number of sent text character
     size_t n_sent_token_probs = 0;
+    size_t n_th_prefix = 0; // size of remaining token healing prefix
 
     int64_t t_start_process_prompt;
     int64_t t_start_generation;
@@ -205,6 +206,7 @@ struct server_slot {
         infill             = false;
         ga_i               = 0;
         n_past_se          = 0;
+        n_th_prefix        = 0;
 
         generated_token_probs.clear();
     }
@@ -1083,6 +1085,36 @@ struct server_context {
             }
         }
 
+        {
+            const auto & token_healing_str = data.find("token_healing");
+            auto & th_enabled = slot.sparams.token_healing_enabled;
+            th_enabled = default_sparams.token_healing_enabled;
+            if (token_healing_str != data.end() && token_healing_str->is_string()) {
+                const auto value = token_healing_str->get<std::string>();
+                auto & th_type = slot.sparams.token_healing_type;
+                auto & th_n_rollback = slot.sparams.token_healing_n_rollback;
+                th_enabled = true;
+                /**/ if (value    == "0" ) { th_enabled = false; }
+                else if (value    == "1" ) { th_type = llama_token_healing_type::ROLLBACK_LAST; }
+                else if (value    == "d1") { th_type = llama_token_healing_type::DYNAMIC_ONCE; }
+                else if (value    == "d" ) { th_type = llama_token_healing_type::DYNAMIC_MULTI; }
+                else if (value[0] == 'r' ) {
+                    th_type = llama_token_healing_type::ROLLBACK_MULTI;
+                    th_n_rollback = std::stoi(value.substr(1));
+                    if (th_n_rollback <= 0) {
+                        th_enabled = false;
+                    }
+                } else { th_enabled = false; }
+
+                LOG_VERBOSE("token healing", {
+                    {"id_slot", slot.id},
+                    {"enabled", th_enabled},
+                    {"type", th_type},
+                    {"n_rollback", th_n_rollback}
+                });
+            }
+        }
+
         {
             if (slot.ctx_sampling != nullptr) {
                 llama_sampling_free(slot.ctx_sampling);
@@ -1178,14 +1210,26 @@ struct server_context {
     }
 
     bool process_token(completion_token_output & result, server_slot & slot) {
-        // remember which tokens were sampled - used for repetition penalties during sampling
         const std::string token_str = llama_token_to_piece(ctx, result.tok, false);
         slot.sampled = result.tok;
-
-        // search stop word and delete it
-        slot.generated_text += token_str;
         slot.has_next_token = true;
 
+        // Suppress generating the token healing prefix to not repeat the input prompt's suffix
+        bool is_token_healing = false;
+        if (slot.n_th_prefix > 0) {
+            if (slot.n_th_prefix < token_str.size()) {
+                slot.generated_text += token_str.substr(slot.n_th_prefix);
+                slot.n_th_prefix = 0;
+                is_token_healing = false;  // to send partial token text when streaming
+            } else {
+                slot.n_th_prefix -= token_str.size();
+                is_token_healing = true;
+            }
+        } else {
+            slot.generated_text += token_str;
+        }
+
+        // remember which tokens were sampled - used for repetition penalties during sampling
         if (slot.ctx_sampling->params.use_penalty_prompt_tokens && result.tok != -1) {
             // we can change penalty_prompt_tokens because it is always created from scratch each request
             slot.ctx_sampling->params.penalty_prompt_tokens.push_back(result.tok);
@@ -1213,7 +1257,7 @@ struct server_context {
             break;
         }
 
-        if (!incomplete) {
+        if (!incomplete && !is_token_healing) {
             size_t pos = std::min(slot.n_sent_text, slot.generated_text.size());
 
             const std::string str_test = slot.generated_text.substr(pos);
@@ -1245,7 +1289,7 @@ struct server_context {
             }
         }
 
-        if (incomplete) {
+        if (incomplete || is_token_healing) {
             slot.has_next_token = true;
         }
 
@@ -1350,7 +1394,8 @@ struct server_context {
             {"n_probs",                   slot.sparams.n_probs},
             {"min_keep",                  slot.sparams.min_keep},
             {"grammar",                   slot.sparams.grammar},
-            {"samplers",                  samplers_sequence}
+            {"samplers",                  samplers_sequence},
+            {"token_healing_enabled",     slot.sparams.token_healing_enabled}
         };
     }
 
@@ -2082,6 +2127,21 @@ struct server_context {
                             continue;
                         }
 
+                        // Roll back prompt tokens if token healing
+                        llama_token_healing_output token_healing_out{};
+                        if (slot.sparams.token_healing_enabled) {
+                            token_healing_out = llama_token_healing_rollback(ctx, slot.sparams.token_healing_type,
+                                prompt_tokens, slot.sparams.token_healing_n_rollback);
+                            slot.n_th_prefix = token_healing_out.prefix.size();
+                            slot.n_prompt_tokens = prompt_tokens.size();
+                            LOG_VERBOSE("token healing prompt", {
+                                {"id_slot", slot.id},
+                                {"id_task", slot.id_task},
+                                {"removed_suffix", token_healing_out.prefix},
+                                {"n_tokens_removed", token_healing_out.n_tokens_removed}
+                            });
+                        }
+
                         if (slot.embedding) {
                             // this prompt is too large to process - discard it
                             if (slot.n_prompt_tokens > n_ubatch) {
@@ -2132,6 +2192,9 @@ struct server_context {
                             }
 
                             llama_sampling_reset(slot.ctx_sampling);
+                            if (slot.sparams.token_healing_enabled) {
+                                llama_token_healing_set_prefix(slot.ctx_sampling, token_healing_out.prefix);
+                            }
 
                             if (!slot.params.cache_prompt) {
                                 slot.n_past_se = 0;