fix bugs when compilei

Author: YuanRisheng

paddle/pten/tests/api/test_elementwise_api.cc

@@ -120,7 +120,7 @@ TEST(API, subtract) {
  auto out = paddle::experimental::subtract(x, y);
 
  // 3. check result
- ASSERT_EQ(out.shape().size(), 2);
+ ASSERT_EQ(out.shape().size(), 2UL);
  ASSERT_EQ(out.shape()[0], 3);
  ASSERT_EQ(out.numel(), 30);
  ASSERT_EQ(out.is_cpu(), true);