[libcxx-commits] [PATCH] D155531: [libc++][PSTL] Simplify the partitioning algorithm until we have better data to know how to chunk better

[Louis Dionne via Phabricator via libcxx-commits]

ldionne accepted this revision.
ldionne added a comment.
This revision is now accepted and ready to land.

LGTM w/ test and passing CI, assuming fixing the CI is just a matter of rebasing and poking the CI.



================
Comment at: libcxx/src/pstl/libdispatch.cpp:26
   partitions.__chunk_size_       = element_count / partitions.__chunk_count_;
-  partitions.__first_chunk_size_ = partitions.__chunk_size_;
-
-  const ptrdiff_t leftover_item_count = element_count - (partitions.__chunk_count_ * partitions.__chunk_size_);
-
-  if (leftover_item_count == 0)
-    return partitions;
-
-  if (leftover_item_count == partitions.__chunk_size_) {
-    partitions.__chunk_count_ += 1;
-    return partitions;
-  }
-
-  const ptrdiff_t n_extra_items_per_chunk = leftover_item_count / partitions.__chunk_count_;
-  const ptrdiff_t n_final_leftover_items  = leftover_item_count - (n_extra_items_per_chunk * partitions.__chunk_count_);
-
-  partitions.__chunk_size_ += n_extra_items_per_chunk;
-  partitions.__first_chunk_size_ = partitions.__chunk_size_ + n_final_leftover_items;
+  partitions.__first_chunk_size_ = element_count - (partitions.__chunk_count_ - 1) * partitions.__chunk_size_;
   return partitions;
----------------
Can you add tests that check the exact values for `element_count` == 0 and 1?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D155531/new/

https://reviews.llvm.org/D155531