server : fix logprobs, make it openai-compatible

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;
@@ -427,9 +433,13 @@ 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},
+                {"id",      p.tok},
-                {"prob",    p.prob},
+                {"token",   tok_str},
+                {"bytes",   str_to_bytes(p.tok_str)},
+                {"logprob", p.prob},
             });
         }
         return probs_for_token;
@@ -437,15 +447,27 @@ struct completion_token_output {
 
     static json probs_vector_to_json(const std::vector<completion_token_output> & probs) {
         json out = json::array();
-        for (const auto & prob : probs) {
+        for (const auto & it : probs) {
-            const std::string tok_str = prob.text_to_send;
+            std::string tok_str(it.text_to_send);
+            tok_str.resize(validate_utf8(tok_str));
             out.push_back(json {
-                {"content", tok_str},
+                {"id",           it.tok},
-                {"probs",   prob.to_json()},
+                {"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},
+        json choice = json{
-                                        {"index", 0},
+            {"finish_reason", finish_reason},
-                                        {"delta", json::object()}}});
+            {"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()) {
+        if (!prob_output.probs.empty()) {
-            res["completion_probabilities"] = completion_token_output::probs_vector_to_json(probs_output);
+            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();
@@ -1713,7 +1749,7 @@ 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
@@ -1721,26 +1757,7 @@ struct server_context {
         slot.has_next_token = true;
 
         // check if there is incomplete UTF-8 character at the end
-        bool incomplete = false;
+        bool incomplete = validate_utf8(slot.generated_text) < slot.generated_text.size();
-        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;
-        }
 
         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);
+            res->prob_output = tkn; // copy the token probs
-
-            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);
-            }
         }
 
         // 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);
+                if (slot.params.sampling.n_probs > 0) {
-
+                    populate_token_probs(slot, result);
-                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 (!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

examples/server/tests/unit/test_chat_completion.py

@@ -92,7 +92,6 @@ def test_chat_completion_with_openai_library():
         seed=42,
         temperature=0.8,
     )
-    print(res)
     assert res.choices[0].finish_reason == "length"
     assert res.choices[0].message.content is not None
     assert match_regex("(Suddenly)+", res.choices[0].message.content)
@@ -163,3 +162,64 @@ def test_chat_completion_with_timings_per_token():
         assert "predicted_per_second" in data["timings"]
         assert "predicted_n" in data["timings"]
         assert data["timings"]["predicted_n"] <= 10
+
+
+def test_logprobs():
+    global server
+    server.start()
+    client = OpenAI(api_key="dummy", base_url=f"http://{server.server_host}:{server.server_port}")
+    res = client.chat.completions.create(
+        model="gpt-3.5-turbo-instruct",
+        temperature=0.0,
+        messages=[
+            {"role": "system", "content": "Book"},
+            {"role": "user", "content": "What is the best book"},
+        ],
+        max_tokens=5,
+        logprobs=True,
+        top_logprobs=10,
+    )
+    output_text = res.choices[0].message.content
+    aggregated_text = ''
+    assert res.choices[0].logprobs is not None
+    assert res.choices[0].logprobs.content is not None
+    for token in res.choices[0].logprobs.content:
+        aggregated_text += token.token
+        assert 0.0 <= token.logprob <= 1.0
+        assert token.bytes is not None and len(token.bytes) > 0
+        assert len(token.top_logprobs) > 0
+    assert aggregated_text == output_text
+
+
+def test_logprobs_stream():
+    global server
+    server.start()
+    client = OpenAI(api_key="dummy", base_url=f"http://{server.server_host}:{server.server_port}")
+    res = client.chat.completions.create(
+        model="gpt-3.5-turbo-instruct",
+        temperature=0.0,
+        messages=[
+            {"role": "system", "content": "Book"},
+            {"role": "user", "content": "What is the best book"},
+        ],
+        max_tokens=5,
+        logprobs=True,
+        top_logprobs=10,
+        stream=True,
+    )
+    output_text = ''
+    aggregated_text = ''
+    for data in res:
+        choice = data.choices[0]
+        if choice.finish_reason is None:
+            if choice.delta.content:
+                output_text += choice.delta.content
+            assert choice.logprobs is not None
+            assert choice.logprobs.content is not None
+            for token in choice.logprobs.content:
+                aggregated_text += token.token
+                assert 0.0 <= token.logprob <= 1.0
+                assert token.bytes is not None and len(token.bytes) > 0
+                assert token.top_logprobs is not None
+                assert len(token.top_logprobs) > 0
+    assert aggregated_text == output_text

examples/server/tests/unit/test_completion.py

@@ -260,9 +260,40 @@ def test_n_probs():
     assert "completion_probabilities" in res.body
     assert len(res.body["completion_probabilities"]) == 5
     for tok in res.body["completion_probabilities"]:
-        assert "probs" in tok
+        assert "id" in tok and tok["id"] > 0
-        assert len(tok["probs"]) == 10
+        assert "token" in tok and type(tok["token"]) == str
-        for prob in tok["probs"]:
+        assert "logprob" in tok and 0.0 <= tok["logprob"] <= 1.0
-            assert "prob" in prob
+        assert "bytes" in tok and len(tok["bytes"]) > 0
-            assert "tok_str" in prob
+        assert len(tok["top_logprobs"]) == 10
-            assert 0.0 <= prob["prob"] <= 1.0
+        for prob in tok["top_logprobs"]:
+            assert "id" in prob and prob["id"] > 0
+            assert "token" in prob and type(prob["token"]) == str
+            assert "logprob" in prob and 0.0 <= prob["logprob"] <= 1.0
+            assert "bytes" in prob and len(prob["bytes"]) > 0
+
+
+def test_n_probs_stream():
+    global server
+    server.start()
+    res = server.make_stream_request("POST", "/completion", data={
+        "prompt": "I believe the meaning of life is",
+        "n_probs": 10,
+        "temperature": 0.0,
+        "n_predict": 5,
+        "stream": True,
+    })
+    for data in res:
+        if data["stop"] == False:
+            assert "completion_probabilities" in data
+            assert len(data["completion_probabilities"]) == 1
+            for tok in data["completion_probabilities"]:
+                assert "id" in tok and tok["id"] > 0
+                assert "token" in tok and type(tok["token"]) == str
+                assert "logprob" in tok and 0.0 <= tok["logprob"] <= 1.0
+                assert "bytes" in tok and len(tok["bytes"]) > 0
+                assert len(tok["top_logprobs"]) == 10
+                for prob in tok["top_logprobs"]:
+                    assert "id" in prob and prob["id"] > 0
+                    assert "token" in prob and type(prob["token"]) == str
+                    assert "logprob" in prob and 0.0 <= prob["logprob"] <= 1.0
+                    assert "bytes" in prob and len(prob["bytes"]) > 0

examples/server/utils.hpp

@@ -170,6 +170,36 @@ static std::vector<llama_tokens> tokenize_input_prompts(llama_context * ctx, con
     return result;
 }
 
+// return the last index of character that can form a valid string
+// if the last character is potentially cut in half, return the index before the cut
+// if validate_utf8(text) == text.size(), then the whole text is valid utf8
+static size_t validate_utf8(const std::string& text) {
+    size_t len = text.size();
+    if (len == 0) return 0;
+
+    // Check the last few bytes to see if a multi-byte character is cut off
+    for (size_t i = 1; i <= 4 && i <= len; ++i) {
+        unsigned char c = text[len - i];
+        // Check for start of a multi-byte sequence from the end
+        if ((c & 0xE0) == 0xC0) {
+            // 2-byte character start: 110xxxxx
+            // Needs at least 2 bytes
+            if (i < 2) return len - i;
+        } else if ((c & 0xF0) == 0xE0) {
+            // 3-byte character start: 1110xxxx
+            // Needs at least 3 bytes
+            if (i < 3) return len - i;
+        } else if ((c & 0xF8) == 0xF0) {
+            // 4-byte character start: 11110xxx
+            // Needs at least 4 bytes
+            if (i < 4) return len - i;
+        }
+    }
+
+    // If no cut-off multi-byte character is found, return full length
+    return len;
+}
+
 //
 // template utils
 //