fix mac unittest bug

test=develop

paddle/fluid/memory/allocation/best_fit_allocator_test.cc

@@ -99,9 +99,8 @@ TEST(BestFitAllocator, test_concurrent_cpu_allocation) {
 
   LockedAllocator locked_allocator(std::move(best_fit_allocator));
 
-  auto th_main = [&] {
-    std::random_device dev;
-    std::default_random_engine engine(dev());
+  auto th_main = [&](std::random_device::result_type seed) {
+    std::default_random_engine engine(seed);
     std::uniform_int_distribution<size_t> dist(1U, 1024U);
 
     for (size_t i = 0; i < 128; ++i) {
@@ -125,7 +124,8 @@ TEST(BestFitAllocator, test_concurrent_cpu_allocation) {
   {
     std::vector<std::thread> threads;
     for (size_t i = 0; i < 1024; ++i) {
-      threads.emplace_back(th_main);
+      std::random_device dev;
+      threads.emplace_back(th_main, dev());
     }
     for (auto& th : threads) {
       th.join();

paddle/fluid/memory/allocation/best_fit_allocator_test.cu

@@ -41,9 +41,8 @@ TEST(BestFitAllocator, concurrent_cuda) {
   LockedAllocator concurrent_allocator(
       std::unique_ptr<Allocator>(new BestFitAllocator(cuda_allocation.get())));
 
-  auto th_main = [&] {
-    std::random_device dev;
-    std::default_random_engine engine(dev());
+  auto th_main = [&](std::random_device::result_type seed) {
+    std::default_random_engine engine(seed);
     std::uniform_int_distribution<size_t> dist(1U, 1024U);
     platform::CUDAPlace gpu(0);
     platform::CUDADeviceContext dev_ctx(gpu);
@@ -75,7 +74,8 @@ TEST(BestFitAllocator, concurrent_cuda) {
   {
     std::vector<std::thread> threads;
     for (size_t i = 0; i < 1024; ++i) {
-      threads.emplace_back(th_main);
+      std::random_device dev;
+      threads.emplace_back(th_main, dev());
     }
     for (auto& th : threads) {
       th.join();