Fix some bug.

paddle/gserver/layers/SliceProjection.cpp

@@ -87,7 +87,7 @@ void SliceProjection::backward(const UpdateCallback& callback) {
     size_t offset = 0;
     for (auto& slice : slices_) {
       auto slice_out = in_->grad->subColMatrix(slice.first, slice.second);
-      slice_out->addAtOffset(*out_->grad, config_.offset());
+      slice_out->addAtOffset(*out_->grad, offset);
       offset += slice_out->getWidth();
     }
   }

paddle/gserver/tests/test_LayerGrad.cpp

@@ -167,7 +167,7 @@ TEST(Projection, slice) {
     testProjectionGrad(conf,
                        INPUT_DATA,
                        /* parameterSize */ 0,
-                       /* batchSize */ 100,
+                       /* batchSize */ 10,
                        useGpu);
   }
 }