server / ranking : add sorting and management of top_n

Author: YannFollet

tools/server/server.cpp

@@ -5061,13 +5061,13 @@ int main(int argc, char ** argv) {
         const json body = json::parse(req.body);
 
         // TODO: implement
-        //int top_n = 1;
-        //if (body.count("top_n") != 1) {
-        //    top_n = body.at("top_n");
-        //} else {
-        //    res_error(res, format_error_response("\"top_n\" must be provided", ERROR_TYPE_INVALID_REQUEST));
-        //    return;
-        //}
+        int top_n = 1;
+        if (body.count("top_n") == 1) {
+            top_n = body.at("top_n");
+        } else {
+            res_error(res, format_error_response("\"top_n\" must be provided", ERROR_TYPE_INVALID_REQUEST));
+            return;
+        }
 
         // if true, use TEI API format, otherwise use Jina API format
         // Jina: https://jina.ai/reranker/
@@ -5133,7 +5133,8 @@ int main(int argc, char ** argv) {
             body,
             responses,
             is_tei_format,
-            documents);
+            documents,
+            top_n);
 
         res_ok(res, root);
     };

tools/server/utils.hpp

@@ -849,46 +849,47 @@ static json format_response_rerank(
         const json & request,
         const json & ranks,
         bool is_tei_format,
-        std::vector<std::string> & texts) {
-    json res;
-    if (is_tei_format) {
-        // TEI response format
-        res = json::array();
-        bool return_text = json_value(request, "return_text", false);
-        for (const auto & rank : ranks) {
-            int index = json_value(rank, "index", 0);
-            json elem = json{
-                {"index", index},
-                {"score", json_value(rank, "score", 0.0)},
-            };
-            if (return_text) {
-                elem["text"] = std::move(texts[index]);
-            }
-            res.push_back(elem);
-        }
-    } else {
-        // Jina response format
-        json results = json::array();
-        int32_t n_tokens = 0;
-        for (const auto & rank : ranks) {
-            results.push_back(json{
-                {"index",           json_value(rank, "index", 0)},
-                {"relevance_score", json_value(rank, "score", 0.0)},
-            });
-
-            n_tokens += json_value(rank, "tokens_evaluated", 0);
+        std::vector<std::string> & texts,
+        int top_n) {
+    json results;
+    int32_t n_tokens = 0;
+    bool return_text = is_tei_format && json_value(request, "return_text", false);
+    std::vector<json> elements; // Temporary vector to hold unsorted elements
+    std::string score_label = is_tei_format ? "score" : "relevance_score";
+    for (const auto & rank : ranks) {
+        int index = json_value(rank, "index", 0);
+        json elem = json{
+            {"index", index},
+            {score_label, json_value(rank, "score", 0.0)},
+        };
+        n_tokens += json_value(rank, "tokens_evaluated", 0);
+        if (return_text) {
+            elem["text"] = std::move(texts[index]);
         }
+        elements.push_back(elem);
+    }
+    
+    std::sort(elements.begin(), elements.end(), [score_label](const json& a, const json& b) {
+        return json_value(a, score_label, 0.0) > json_value(b, score_label, 0.0);
+    });
 
-        res = json{
-            {"model", json_value(request, "model", std::string(DEFAULT_OAICOMPAT_MODEL))},
-            {"object", "list"},
-            {"usage", json{
-                {"prompt_tokens", n_tokens},
-                {"total_tokens", n_tokens}
-            }},
-            {"results", results}
-        };
+    results = json::array();
+    int count = 0;
+    for (const auto & elem : elements) {
+        if (++count > top_n) break;
+        results.push_back(elem);
     }
+    if (is_tei_format) return results;
+
+    json res = json{
+        {"model", json_value(request, "model", std::string(DEFAULT_OAICOMPAT_MODEL))},
+        {"object", "list"},
+        {"usage", json{
+            {"prompt_tokens", n_tokens},
+            {"total_tokens", n_tokens}
+        }},
+        {"results", results}
+    };
 
     return res;
 }