fix sampling id op bug (#16909)

* fix sampling id op bug, test=develop

paddle/fluid/operators/sampling_id_op.cc

@@ -28,15 +28,15 @@ class SamplingIdOp : public framework::OperatorWithKernel {
                    "Input(X) of SamplingIdOp should not be null.");
     PADDLE_ENFORCE(ctx->HasOutput("Out"),
                    "Output(Out) of SamplingIdOp should not be null.");
-    PADDLE_ENFORCE(
-        ctx->Attrs().Get<float>("min") < ctx->Attrs().Get<float>("max"),
-        "min must less then max");
+    PADDLE_ENFORCE_LT(ctx->Attrs().Get<float>("min"),
+                      ctx->Attrs().Get<float>("max"), "min must less then max");
 
     auto input_dims = ctx->GetInputDim("X");
     PADDLE_ENFORCE(input_dims.size() == 2,
                    "Input(X, Filter) should be 2-D tensor.");
 
-    framework::DDim dims = input_dims;
+    auto dim0 = input_dims[0];
+    framework::DDim dims = framework::make_ddim({dim0});
     ctx->SetOutputDim("Out", dims);
     ctx->ShareLoD("X", "Out");
   }

python/paddle/fluid/tests/unittests/test_sampling_id_op.py

@@ -17,6 +17,7 @@ import numpy as np
 from op_test import OpTest
 
 import paddle.fluid.core as core
+import paddle.fluid as fluid
 from paddle.fluid.op import Operator
 
 
@@ -57,5 +58,26 @@ class TestSamplingIdOp(OpTest):
         pass
 
 
+class TestSamplingIdShape(unittest.TestCase):
+    def test_shape(self):
+        x = fluid.layers.data(name='x', shape=[3], dtype='float32')
+        output = fluid.layers.sampling_id(x)
+
+        place = fluid.CPUPlace()
+        exe = fluid.Executor(place=place)
+        exe.run(fluid.default_startup_program())
+
+        feed = {
+            'x': np.array(
+                [[0.2, 0.3, 0.5], [0.2, 0.3, 0.4]], dtype='float32')
+        }
+        output_np = exe.run(feed=feed, fetch_list=[output])[0]
+
+        self.assertEqual(output.shape[0], -1)
+        self.assertEqual(len(output.shape), 1)
+        self.assertEqual(output_np.shape[0], 2)
+        self.assertEqual(len(output_np.shape), 1)
+
+
 if __name__ == "__main__":
     unittest.main()