fix bug on ClipLayer test in test_LayerGrad

paddle/gserver/tests/test_LayerGrad.cpp

@@ -1907,8 +1907,10 @@ TEST(Layer, ClipLayer) {
   config.inputDefs.push_back({INPUT_DATA, "input", size, 0});
   LayerInputConfig* input = config.layerConfig.add_inputs();
   ClipConfig* layerConf = input->mutable_clip_conf();
-  layerConf->set_min(std::rand() / (double)RAND_MAX);
-  layerConf->set_max(std::rand() / (double)RAND_MAX);
+  double p1 = std::rand() / (double)RAND_MAX;
+  double p2 = std::rand() / (double)RAND_MAX;
+  layerConf->set_min(std::min(p1, p2));
+  layerConf->set_max(std::max(p1, p2));
   for (auto useGpu : {false, true}) {
     testLayerGrad(config, "clip", batchSize, false, useGpu, false);
   }