server : fix logprobs, make it OAI-compatible

examples/server/README.md

@@ -343,6 +343,10 @@ node index.js
 
 ### POST `/completion`: Given a `prompt`, it returns the predicted completion.
 
+> [!IMPORTANT]
+>
+> This endpoint is **not** OAI-compatible
+
 *Options:*
 
 `prompt`: Provide the prompt for this completion as a string or as an array of strings or numbers representing tokens. Internally, if `cache_prompt` is `true`, the prompt is compared to the previous completion and only the "unseen" suffix is evaluated. A `BOS` token is inserted at the start, if all of the following conditions are true:
@@ -448,27 +452,48 @@ These words will not be included in the completion, so make sure to add them to
 
 - Note: When using streaming mode (`stream`), only `content` and `stop` will be returned until end of completion.
 
-- `completion_probabilities`: An array of token probabilities for each completion. The array's length is `n_predict`. Each item in the array has the following structure:
+- `completion_probabilities`: An array of token probabilities for each completion. The array's length is `n_predict`. Each item in the array has a nested array `top_logprobs`. It contains at **maximum** `n_probs` elements:
 
 ```json
 {
-  "content": "<the token selected by the model>",
-  "probs": [
+  "content": "<the generated completion text>",
+  ...
+  "completion_probabilities": [
     {
+      "id": <token id>,
       "prob": float,
-      "tok_str": "<most likely token>"
+      "token": "<most likely token>",
+      "bytes": [int, int, ...],
+      "top_logprobs": [
+        {
+          "id": <token id>,
+          "prob": float,
+          "token": "<token text>",
+          "bytes": [int, int, ...],
+        },
+        {
+          "id": <token id>,
+          "prob": float,
+          "token": "<token text>",
+          "bytes": [int, int, ...],
+        },
+        ...
+      ]
     },
     {
+      "id": <token id>,
       "prob": float,
-      "tok_str": "<second most likely token>"
+      "token": "<most likely token>",
+      "bytes": [int, int, ...],
+      "top_logprobs": [
+        ...
+      ]
     },
     ...
   ]
 },
 ```
 
-Notice that each `probs` is an array of length `n_probs`.
-
 - `content`: Completion result as a string (excluding `stopping_word` if any). In case of streaming mode, will contain the next token as a string.
 - `stop`: Boolean for use with `stream` to check whether the generation has stopped (Note: This is not related to stopping words array `stop` from input options)
 - `generation_settings`: The provided options above excluding `prompt` but including `n_ctx`, `model`. These options may differ from the original ones in some way (e.g. bad values filtered out, strings converted to tokens, etc.).

examples/server/server.cpp

@@ -342,6 +342,11 @@ struct server_task {
             }
         }
 
+        if (params.sampling.n_probs > 0 && params.cache_prompt) {
+            SRV_WRN("cache_prompt is not compatible with n_probs > 0 (current value = %d), disabling cache_prompt.\n", params.sampling.n_probs);
+            params.cache_prompt = false;
+        }
+
         std::string model_name = params_base.model_alias.empty() ? DEFAULT_OAICOMPAT_MODEL : params_base.model_alias;
         params.oaicompat_model = json_value(data, "model", model_name);
 
@@ -416,6 +421,7 @@ inline std::string stop_type_to_str(stop_type type) {
 
 struct completion_token_output {
     llama_token tok;
+    float prob;
     std::string text_to_send;
     struct token_prob {
         llama_token tok;
@@ -427,25 +433,41 @@ struct completion_token_output {
     json to_json() const {
         json probs_for_token = json::array();
         for (const auto & p : probs) {
+            std::string tok_str(p.tok_str);
+            tok_str.resize(validate_utf8(tok_str));
             probs_for_token.push_back(json {
-                {"tok_str", p.tok_str},
-                {"prob",    p.prob},
+                {"id",      p.tok},
+                {"token",   tok_str},
+                {"bytes",   str_to_bytes(p.tok_str)},
+                {"logprob", p.prob},
             });
         }
         return probs_for_token;
     }
 
     static json probs_vector_to_json(const std::vector<completion_token_output> & probs) {
         json out = json::array();
-        for (const auto & prob : probs) {
-            const std::string tok_str = prob.text_to_send;
+        for (const auto & it : probs) {
+            std::string tok_str(it.text_to_send);
+            tok_str.resize(validate_utf8(tok_str));
             out.push_back(json {
-                {"content", tok_str},
-                {"probs",   prob.to_json()},
+                {"id",           it.tok},
+                {"token",        tok_str},
+                {"logprob",      it.prob},
+                {"bytes",        str_to_bytes(it.text_to_send)},
+                {"top_logprobs", it.to_json()},
             });
         }
         return out;
     }
+
+    static std::vector<unsigned char> str_to_bytes(const std::string & str) {
+        std::vector<unsigned char> bytes;
+        for (unsigned char c : str) {
+            bytes.push_back(c);
+        }
+        return bytes;
+    }
 };
 
 struct server_task_result_cmpl_final : server_task_result {
@@ -506,7 +528,7 @@ struct server_task_result_cmpl_final : server_task_result {
             {"tokens_cached",       n_tokens_cached},
             {"timings",             timings.to_json()},
         };
-        if (!probs_output.empty()) {
+        if (!stream && !probs_output.empty()) {
             res["completion_probabilities"] = completion_token_output::probs_vector_to_json(probs_output);
         }
         return res;
@@ -518,19 +540,25 @@ struct server_task_result_cmpl_final : server_task_result {
             finish_reason = "stop";
         }
 
-        json choices = json::array({json{
+        json choice = json{
             {"finish_reason", finish_reason},
             {"index", 0},
             {"message", json{
                 {"content", content},
                 {"role", "assistant"}
             }
-        }}});
+        }};
+
+        if (!stream && probs_output.size() > 0) {
+            choice["logprobs"] = json{
+                {"content", completion_token_output::probs_vector_to_json(probs_output)},
+            };
+        }
 
         std::time_t t = std::time(0);
 
         json res = json {
-            {"choices", choices},
+            {"choices", json::array({choice})},
             {"created", t},
             {"model", oaicompat_model},
             {"object", "chat.completion"},
@@ -560,12 +588,14 @@ struct server_task_result_cmpl_final : server_task_result {
             finish_reason = "stop";
         }
 
-        json choices = json::array({json{{"finish_reason", finish_reason},
-                                        {"index", 0},
-                                        {"delta", json::object()}}});
+        json choice = json{
+            {"finish_reason", finish_reason},
+            {"index", 0},
+            {"delta", json::object()}
+        };
 
         json ret = json {
-            {"choices", choices},
+            {"choices", json::array({choice})},
             {"created", t},
             {"id",      oaicompat_cmpl_id},
             {"model",   oaicompat_model},
@@ -592,7 +622,7 @@ struct server_task_result_cmpl_partial : server_task_result {
     int32_t n_decoded;
     int32_t n_prompt_tokens;
 
-    std::vector<completion_token_output> probs_output;
+    completion_token_output prob_output;
     result_timings timings;
 
     // OAI-compat fields
@@ -628,8 +658,8 @@ struct server_task_result_cmpl_partial : server_task_result {
         if (timings.prompt_n > 0) {
             res.push_back({"timings", timings.to_json()});
         }
-        if (!probs_output.empty()) {
-            res["completion_probabilities"] = completion_token_output::probs_vector_to_json(probs_output);
+        if (!prob_output.probs.empty()) {
+            res["completion_probabilities"] = completion_token_output::probs_vector_to_json({prob_output});
         }
         return res;
     }
@@ -681,6 +711,14 @@ struct server_task_result_cmpl_partial : server_task_result {
             }});
         }
 
+        GGML_ASSERT(choices.size() >= 1);
+
+        if (prob_output.probs.size() > 0) {
+            choices[0]["logprobs"] = json{
+                {"content", completion_token_output::probs_vector_to_json({prob_output})},
+            };
+        }
+
         json ret = json {
             {"choices", choices},
             {"created", t},
@@ -951,7 +989,6 @@ struct server_slot {
 
     // stats
     size_t n_sent_text        = 0; // number of sent text character
-    size_t n_sent_token_probs = 0;
 
     int64_t t_start_process_prompt;
     int64_t t_start_generation;
@@ -973,7 +1010,6 @@ struct server_slot {
         stopping_word      = "";
         n_past             = 0;
         n_sent_text        = 0;
-        n_sent_token_probs = 0;
         task_type          = SERVER_TASK_TYPE_COMPLETION;
 
         generated_token_probs.clear();
@@ -1713,34 +1749,15 @@ 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 = common_token_to_piece(ctx, result.tok, params_base.special);
+        const std::string token_str = result.text_to_send;
         slot.sampled = result.tok;
 
         // search stop word and delete it
         slot.generated_text += token_str;
         slot.has_next_token = true;
 
         // check if there is incomplete UTF-8 character at the end
-        bool incomplete = false;
-        for (unsigned i = 1; i < 5 && i <= slot.generated_text.size(); ++i) {
-            unsigned char c = slot.generated_text[slot.generated_text.size() - i];
-            if ((c & 0xC0) == 0x80) {
-                // continuation byte: 10xxxxxx
-                continue;
-            }
-            if ((c & 0xE0) == 0xC0) {
-                // 2-byte character: 110xxxxx ...
-                incomplete = i < 2;
-            } else if ((c & 0xF0) == 0xE0) {
-                // 3-byte character: 1110xxxx ...
-                incomplete = i < 3;
-            } else if ((c & 0xF8) == 0xF0) {
-                // 4-byte character: 11110xxx ...
-                incomplete = i < 4;
-            }
-            // else 1-byte character or invalid byte
-            break;
-        }
+        bool incomplete = validate_utf8(slot.generated_text) < slot.generated_text.size();
 
         if (!incomplete) {
             size_t pos = std::min(slot.n_sent_text, slot.generated_text.size());
@@ -1869,6 +1886,29 @@ struct server_context {
         return slot.has_next_token; // continue
     }
 
+    void populate_token_probs(const server_slot & slot, completion_token_output & result) {
+        const auto * cur_p = common_sampler_get_candidates(slot.smpl);
+        const size_t max_probs = cur_p->size;
+
+        // set prob for the sampled token
+        for (size_t i = 0; i < max_probs; ++i) {
+            if (result.tok == cur_p->data[i].id) {
+                result.prob = cur_p->data[i].p;
+                break;
+            }
+        }
+
+        // set probs for the top n tokens
+        for (size_t i = 0; i < std::min(max_probs, (size_t) slot.params.sampling.n_probs); ++i) {
+            auto tok_id = cur_p->data[i].id;
+            result.probs.push_back({
+                tok_id,
+                tokens_to_output_formatted_string(ctx, tok_id),
+                cur_p->data[i].p,
+            });
+        }
+    }
+
     void send_error(const server_task & task, const std::string & error, const enum error_type type = ERROR_TYPE_SERVER) {
         send_error(task.id, error, type);
     }
@@ -1906,17 +1946,7 @@ struct server_context {
 
         // populate res.probs_output
         if (slot.params.sampling.n_probs > 0) {
-            const llama_tokens to_send_toks = common_tokenize(ctx, tkn.text_to_send, false);
-
-            const size_t probs_pos      = std::min(slot.n_sent_token_probs,                       slot.generated_token_probs.size());
-            const size_t probs_stop_pos = std::min(slot.n_sent_token_probs + to_send_toks.size(), slot.generated_token_probs.size());
-
-            std::vector<completion_token_output> probs_output;
-            if (probs_pos < probs_stop_pos) {
-                res->probs_output = std::vector<completion_token_output>(
-                        slot.generated_token_probs.begin() + probs_pos,
-                        slot.generated_token_probs.begin() + probs_stop_pos);
-            }
+            res->prob_output = tkn; // copy the token probs
         }
 
         // populate timings if this is final response or timings_per_token is enabled
@@ -2747,17 +2777,12 @@ struct server_context {
                 slot.t_token_generation = (t_current - slot.t_start_generation) / 1e3;
 
                 completion_token_output result;
-                result.tok = id;
+                result.tok          = id;
+                result.text_to_send = common_token_to_piece(ctx, result.tok, params_base.special);
+                result.prob         = 1.0f; // set later
 
-                const auto * cur_p = common_sampler_get_candidates(slot.smpl);
-
-                for (size_t i = 0; i < (size_t) slot.params.sampling.n_probs; ++i) {
-                    auto tok_id = cur_p->data[i].id;
-                    result.probs.push_back({
-                        tok_id,
-                        tokens_to_output_formatted_string(ctx, tok_id),
-                        i >= cur_p->size ? 0.0f : cur_p->data[i].p,
-                    });
+                if (slot.params.sampling.n_probs > 0) {
+                    populate_token_probs(slot, result);
                 }
 
                 if (!process_token(result, slot)) {
@@ -2841,7 +2866,9 @@ struct server_context {
                 for (size_t i = 0; i < ids.size(); ++i) {
                     completion_token_output result;
 
-                    result.tok = ids[i];
+                    result.tok          = ids[i];
+                    result.text_to_send = common_token_to_piece(ctx, result.tok, params_base.special);
+                    result.prob         = 1.0f; // set later
 
                     if (!process_token(result, slot)) {
                         // release slot because of stop condition