fix matmul shape check; test=develop

paddle/fluid/operators/matmul_op.cc

@@ -290,8 +290,10 @@ class MatMulOp : public framework::OperatorWithKernel {
                                      context->Attrs().Get<bool>("transpose_Y"));
 
     PADDLE_ENFORCE_EQ(mat_dim_x.width_, mat_dim_y.height_);
+    if (context->IsRuntime()) {
       PADDLE_ENFORCE(mat_dim_x.batch_size_ == mat_dim_y.batch_size_ ||
                      mat_dim_x.batch_size_ == 0 || mat_dim_y.batch_size_ == 0);
+    }
     std::vector<int64_t> dim_out;
     if (mat_dim_x.batch_size_ != 0) {
       dim_out = framework::vectorize(dim_x);

python/paddle/fluid/layers/nn.py

@@ -4901,6 +4901,9 @@ def matmul(x, y, transpose_x=False, transpose_y=False, alpha=1.0, name=None):
 
         if len(y_shape) > 2 and len(x_shape) > 2:
             for i, dim_x in enumerate(x_shape[:-2]):
+                # don't check neg shape
+                if dim_x < 0 or y_shape[i] < 0:
+                    continue
                 if dim_x != y_shape[i]:
                     raise ValueError("Invalid inputs for matmul. x(%s), y(%s)" %
                                      (x.shape, y.shape))