fix assertion 'index out of bounds' in case dim_size is omitted

csrc/cuda/scatter_cuda.cu

@@ -84,10 +84,7 @@ scatter_cuda(torch::Tensor src, torch::Tensor index, int64_t dim,
     else if (index.numel() == 0)
       sizes[dim] = 0;
     else {
-      auto d_size = index.max().data_ptr<int64_t>();
-      auto h_size = (int64_t *)malloc(sizeof(int64_t));
-      cudaMemcpy(h_size, d_size, sizeof(int64_t), cudaMemcpyDeviceToHost);
-      sizes[dim] = 1 + *h_size;
+      sizes[dim] = 1 + index.max().cpu().data_ptr<int64_t>()[0];
     }
     out = torch::empty(sizes, src.options());
   }

csrc/cuda/segment_coo_cuda.cu

@@ -186,10 +186,7 @@ segment_coo_cuda(torch::Tensor src, torch::Tensor index,
     else {
       auto tmp = index.select(dim, index.size(dim) - 1);
       tmp = tmp.numel() > 1 ? tmp.max() : tmp;
-      auto d_size = tmp.data_ptr<int64_t>();
-      auto h_size = (int64_t *)malloc(sizeof(int64_t));
-      cudaMemcpy(h_size, d_size, sizeof(int64_t), cudaMemcpyDeviceToHost);
-      sizes[dim] = 1 + *h_size;
+      sizes[dim] = 1 + tmp.cpu().data_ptr<int64_t>()[0];
     }
     out = torch::zeros(sizes, src.options());
   }

csrc/cuda/segment_csr_cuda.cu

@@ -245,12 +245,10 @@ torch::Tensor gather_csr_cuda(torch::Tensor src, torch::Tensor indptr,
   } else {
     auto sizes = src.sizes().vec();
     if (src.numel() > 0) {
-      auto d_size = indptr.flatten()[-1].data_ptr<int64_t>();
-      auto h_size = (int64_t *)malloc(sizeof(int64_t));
-      cudaMemcpy(h_size, d_size, sizeof(int64_t), cudaMemcpyDeviceToHost);
-      sizes[dim] = *h_size;
-    } else
+      sizes[dim] = indptr.flatten()[-1].cpu().data_ptr<int64_t>()[0];
+    } else {
       sizes[dim] = 0;
+    }
     out = torch::empty(sizes, src.options());
   }