fix split infer shape; test=develop

paddle/fluid/operators/split_op.cc

@@ -39,6 +39,7 @@ class SplitOp : public framework::OperatorWithKernel {
 
     if (num > 0) {
       int64_t in_axis_dim = in_dims[axis];
+      if (ctx->IsRuntime() || in_axis_dim > 0) {
         PADDLE_ENFORCE_EQ(in_axis_dim % num, 0,
                           "tensor split does not result"
                           " in an equal division");
@@ -48,6 +49,13 @@ class SplitOp : public framework::OperatorWithKernel {
           dim[axis] = out_axis_dim;
           outs_dims.push_back(dim);
         }
+      } else {
+        for (size_t i = 0; i < outs_number; ++i) {
+          auto dim = in_dims;
+          dim[axis] = -1;
+          outs_dims.push_back(dim);
+        }
+      }
     } else if (sections.size() > 0) {
       PADDLE_ENFORCE_EQ(sections.size(), outs_number,
                         "tensor split sections size"