fix index

paddle/fluid/operators/roi_pool_op.cu

@@ -38,10 +38,10 @@ __global__ void GPUROIPoolForward(
   int index = blockIdx.x * blockDim.x + threadIdx.x;
   int offset = blockDim.x * gridDim.x;
   for (size_t i = index; i < nthreads; i += offset) {
-    int pw = index % pooled_width;
-    int ph = (index / pooled_width) % pooled_height;
-    int c = (index / pooled_width / pooled_height) % channels;
-    int n = index / pooled_width / pooled_height / channels;
+    int pw = i % pooled_width;
+    int ph = (i / pooled_width) % pooled_height;
+    int c = (i / pooled_width / pooled_height) % channels;
+    int n = i / pooled_width / pooled_height / channels;
 
     const int64_t* offset_input_rois = input_rois + n * kROISize;
     int roi_batch_ind = roi_batch_id_data[n];
@@ -65,7 +65,6 @@ __global__ void GPUROIPoolForward(
     int wend = static_cast<int>(ceil(static_cast<double>(pw + 1) *
                                      static_cast<double>(roi_width) /
                                      static_cast<double>(pooled_width)));
-
     hstart = min(max(hstart + roi_start_h, 0), height);
     hend = min(max(hend + roi_start_h, 0), height);
     wstart = min(max(wstart + roi_start_w, 0), width);
@@ -85,9 +84,9 @@ __global__ void GPUROIPoolForward(
         }
       }
     }
-    output_data[index] = maxval;
+    output_data[i] = maxval;
     if (argmax_data) {
-      argmax_data[index] = maxidx;
+      argmax_data[i] = maxidx;
     }
   }
 }
@@ -144,6 +143,7 @@ class GPUROIPoolOpKernel : public framework::OpKernel<T> {
     int width = in_dims[3];
 
     int rois_num = rois->dims()[0];
+
     if (rois_num == 0) return;
 
     int output_size = out->numel();