add init_gflags interface (#5193)

* add init_gflags interface

* refine code

* follow comments

paddle/pybind/pybind.cc

@@ -14,6 +14,8 @@ limitations under the License. */
 
 #include "paddle/pybind/protobuf.h"
 
+#include <mutex>  // for call_once
+#include "gflags/gflags.h"
 #include "paddle/framework/backward.h"
 #include "paddle/framework/executor.h"
 #include "paddle/framework/feed_fetch_method.h"
@@ -45,6 +47,24 @@ static size_t UniqueIntegerGenerator() {
   return generator.fetch_add(1);
 }
 
+std::once_flag gflags_init_flag;
+
+// TODO(qijun) move init gflags to init.cc
+void InitGflags(std::vector<std::string> &argv) {
+  std::call_once(gflags_init_flag, [&]() {
+    int argc = argv.size();
+    char **arr = new char *[argv.size()];
+    std::string line;
+    for (size_t i = 0; i < argv.size(); i++) {
+      arr[i] = &argv[i][0];
+      line += argv[i];
+      line += ' ';
+    }
+    google::ParseCommandLineFlags(&argc, &arr, true);
+    VLOG(1) << "Init commandline: " << line;
+  });
+}
+
 bool IsCompileGPU() {
 #ifndef PADDLE_WITH_CUDA
   return false;
@@ -483,6 +503,7 @@ All parameter, weight, gradient are variables in Paddle.
       });
 
   m.def("unique_integer", UniqueIntegerGenerator);
+  m.def("init_gflags", InitGflags);
 
   m.def("is_compile_gpu", IsCompileGPU);
   m.def("set_feed_variable", framework::SetFeedVariable);

python/paddle/v2/framework/__init__.py

+import sys
+import core
 __all__ = ['proto']
+argv = []
+if core.is_compile_gpu():
+    argv = list(sys.argv) + [
+        "--tryfromenv=fraction_of_gpu_memory_to_use,use_pinned_memory"
+    ]
+else:
+    argv = list(sys.argv) + ["--tryfromenv=use_pinned_memory"]
+core.init_gflags(argv)