improve the performance of capi in PD_PredictorRun (#20665)

paddle/fluid/inference/capi/pd_predictor.cc

@@ -29,7 +29,13 @@ bool PD_PredictorRun(const PD_AnalysisConfig* config, PD_Tensor* inputs,
                      int in_size, PD_Tensor* output_data, int** out_size,
                      int batch_size) {
   PADDLE_ENFORCE_NOT_NULL(config);
-  auto predictor = paddle::CreatePaddlePredictor(config->config);
+  static std::map<std::string, std::unique_ptr<paddle::PaddlePredictor>>
+      predictors;
+  if (!predictors.count(config->config.model_dir())) {
+    predictors[config->config.model_dir()] =
+        paddle::CreatePaddlePredictor(config->config);
+  }
+  auto& predictor = predictors[config->config.model_dir()];
   std::vector<paddle::PaddleTensor> in;
   for (int i = 0; i < in_size; ++i) {
     in.emplace_back(inputs->tensor);