refine batch_norm

Author: chengduoZH

paddle/operators/batch_norm_op.cc

@@ -50,10 +50,6 @@ class BatchNormOp : public framework::OperatorWithKernel {
     PADDLE_ENFORCE(ctx->HasOutput("SavedMean"), "");
     PADDLE_ENFORCE(ctx->HasOutput("SavedVariance"), "");
 
-    const float epsilon = ctx->Attrs().Get<float>("epsilon");
-    PADDLE_ENFORCE_GE(epsilon, 0.0, "epsilon should be larger than 0");
-    PADDLE_ENFORCE_LE(epsilon, 0.001, "epsilon should not be too large");
-
     // make sure Mean/MeanOut and Variance/VarianceOut share memory in Python
     PADDLE_ENFORCE_EQ(ctx->Inputs("Mean")[0], ctx->Outputs("MeanOut")[0],
                       "Mean and MeanOut should share the same memory");
@@ -91,7 +87,12 @@ class BatchNormOpMaker : public framework::OpProtoAndCheckerMaker {
       : OpProtoAndCheckerMaker(proto, op_checker) {
     AddAttr<bool>("is_test", "").SetDefault(false);
     AddAttr<float>("momentum", "").SetDefault(0.9);
-    AddAttr<float>("epsilon", "").SetDefault(1e-5);
+    AddAttr<float>("epsilon", "")
+        .SetDefault(1e-5)
+        .AddCustomChecker([](const float &epsilon) {
+          PADDLE_ENFORCE(epsilon >= 0.0f && epsilon <= 0.001f,
+                         "'epsilon' should be between 0.0 and 0.001.");
+        });
     AddAttr<std::string>("data_layout", "").SetDefault("NCHW");
     AddInput("X", "The input tensor");
     AddInput("Scale",