Simplify write-out kernels in topk implementation (avoid recomputing gid)

Author: oleksandr-pavlyk

dpctl/tensor/libtensor/include/kernels/sorting/topk.hpp

@@ -417,17 +417,17 @@ sycl::event topk_merge_impl(
                 topk_partial_merge_map_back_krn<argTy, IndexTy, ValueComp>;
 
             cgh.parallel_for<KernelName>(iter_nelems * k, [=](sycl::id<1> id) {
-                std::size_t gid = id[0];
+                const std::size_t gid = id[0];
 
-                std::size_t iter_gid = gid / k;
-                std::size_t axis_gid = gid - (iter_gid * k);
+                const std::size_t iter_gid = gid / k;
+                const std::size_t axis_gid = gid - (iter_gid * k);
 
-                std::size_t src_idx = iter_gid * alloc_len + axis_gid;
-                std::size_t dst_idx = iter_gid * k + axis_gid;
+                const std::size_t src_idx = iter_gid * alloc_len + axis_gid;
+                const std::size_t dst_idx = gid;
 
-                auto res_ind = index_data[src_idx];
+                const auto res_ind = index_data[src_idx];
                 vals_tp[dst_idx] = arg_tp[res_ind];
-                inds_tp[dst_idx] = res_ind % axis_nelems;
+                inds_tp[dst_idx] = (res_ind % axis_nelems);
             });
         });
 
@@ -529,17 +529,17 @@ sycl::event topk_radix_impl(sycl::queue &exec_q,
         using KernelName = topk_radix_map_back_krn<argTy, IndexTy>;
 
         cgh.parallel_for<KernelName>(iter_nelems * k, [=](sycl::id<1> id) {
-            std::size_t gid = id[0];
+            const std::size_t gid = id[0];
 
-            std::size_t iter_gid = gid / k;
-            std::size_t axis_gid = gid - (iter_gid * k);
+            const std::size_t iter_gid = gid / k;
+            const std::size_t axis_gid = gid - (iter_gid * k);
 
-            std::size_t src_idx = iter_gid * axis_nelems + axis_gid;
-            std::size_t dst_idx = iter_gid * k + axis_gid;
+            const std::size_t src_idx = iter_gid * axis_nelems + axis_gid;
+            const std::size_t dst_idx = gid;
 
-            IndexTy res_ind = tmp_tp[src_idx];
+            const IndexTy res_ind = tmp_tp[src_idx];
             vals_tp[dst_idx] = arg_tp[res_ind];
-            inds_tp[dst_idx] = res_ind % axis_nelems;
+            inds_tp[dst_idx] = (res_ind % axis_nelems);
         });
     });