fix for pytorch 1.6.0

csrc/cpu/grid_cpu.cpp

@@ -32,13 +32,13 @@ torch::Tensor grid_cpu(torch::Tensor pos, torch::Tensor size,
 
   pos = pos - start.unsqueeze(0);
 
-  auto num_voxels = ((end - start) / size).toType(torch::kLong) + 1;
+  auto num_voxels = (end - start).true_divide(size).toType(torch::kLong) + 1;
   num_voxels = num_voxels.cumprod(0);
   num_voxels =
       torch::cat({torch::ones(1, num_voxels.options()), num_voxels}, 0);
   num_voxels = num_voxels.narrow(0, 0, size.size(0));
 
-  auto out = (pos / size.view({1, -1})).toType(torch::kLong);
+  auto out = pos.true_divide(size.view({1, -1})).toType(torch::kLong);
   out *= num_voxels.view({1, -1});
   out = out.sum(1);