for predetect download data

paddle/fluid/train/custom_trainer/feed/common/pipeline.h

@@ -116,7 +116,7 @@ private:
                 }
                 parsing_num += read_size;
                 BthreadTaskRunner::instance().add_task(
-                    [this, &parsing_num, read_size, input_data_buffer](){
+                    [this, &parsing_num, read_size, input_data_buffer]() {
                     size_t write_size = 0;
                     std::vector<TypeOut> output_data_buffer(_options.batch_size);
                     _converter(input_data_buffer->data(), read_size,

paddle/fluid/train/custom_trainer/feed/process/learner_process.cc

@@ -215,6 +215,7 @@ int LearnerProcess::run() {
         //Step1. 等待样本ready
         {
             ENVLOG_WORKER_MASTER_NOTICE("      %s, wait data ready:%s", epoch_log_title.c_str(), data_path.c_str());
+            dataset->pre_detect_data(epoch_id);
             while (dataset->epoch_data_status(epoch_id) != DatasetStatus::Ready) {
                 sleep(30);  
                 dataset->pre_detect_data(epoch_id);