add std::log

Author: ngxson

examples/server/server.cpp

@@ -342,11 +342,6 @@ 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);
 
@@ -439,7 +434,7 @@ struct completion_token_output {
                 {"id",      p.tok},
                 {"token",   tok_str},
                 {"bytes",   str_to_bytes(p.tok_str)},
-                {"logprob", p.prob},
+                {"logprob", logarithm(p.prob)},
             });
         }
         return probs_for_token;
@@ -453,14 +448,19 @@ struct completion_token_output {
             out.push_back(json {
                 {"id",           it.tok},
                 {"token",        tok_str},
-                {"logprob",      it.prob},
+                {"logprob",      logarithm(it.prob)},
                 {"bytes",        str_to_bytes(it.text_to_send)},
                 {"top_logprobs", it.to_json()},
             });
         }
         return out;
     }
 
+    static float logarithm(float x) {
+        // nlohmann::json converts -inf to null, so we need to prevent that
+        return x == 0.0f ? std::numeric_limits<float>::lowest() : std::log(x);
+    }
+
     static std::vector<unsigned char> str_to_bytes(const std::string & str) {
         std::vector<unsigned char> bytes;
         for (unsigned char c : str) {

examples/server/tests/unit/test_chat_completion.py

@@ -185,7 +185,7 @@ def test_logprobs():
     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.logprob <= 0.0
         assert token.bytes is not None and len(token.bytes) > 0
         assert len(token.top_logprobs) > 0
     assert aggregated_text == output_text
@@ -218,7 +218,7 @@ def test_logprobs_stream():
             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.logprob <= 0.0
                 assert token.bytes is not None and len(token.bytes) > 0
                 assert token.top_logprobs is not None
                 assert len(token.top_logprobs) > 0

examples/server/tests/unit/test_completion.py

@@ -262,13 +262,13 @@ def test_n_probs():
     for tok in res.body["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 "logprob" in tok and tok["logprob"] <= 0.0
         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 "logprob" in prob and prob["logprob"] <= 0.0
             assert "bytes" in prob and len(prob["bytes"]) > 0
 
 
@@ -289,11 +289,11 @@ def test_n_probs_stream():
             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 "logprob" in tok and tok["logprob"] <= 0.0
                 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 "logprob" in prob and prob["logprob"] <= 0.0
                     assert "bytes" in prob and len(prob["bytes"]) > 0