Bug 22745 – std.parallelism.parallel fails to process empty range on a single CPU

On a VM where I have allocated one core, std.parallelism.parallel fails with the message: workUnitSize must be > 0 This comes from the following code: ```d int main() { import std.stdio; import std.parallelism; int[] arr; foreach(i; arr.parallel) { writeln(i); } } ``` Why does it fail? Here is the code that throws the error: https://github.com/dlang/phobos/blob/ab4008c13f593b35adc7ec2229e299e73c182930/std/parallelism.d#L1631 Note that the workUnitSize is passed in from the default work unit size. That is determined via this function: https://github.com/dlang/phobos/blob/ab4008c13f593b35adc7ec2229e299e73c182930/std/parallelism.d#L1631 The `size` value is set determined by the number of cores here: https://github.com/dlang/phobos/blob/ab4008c13f593b35adc7ec2229e299e73c182930/std/parallelism.d#L1524 Note that if "size" is zero (having 1 core), and the range is zero length, then the workUnitSize will be zero. I'd suspect a fix is to check if the range is empty and immediately return before getting this far.

@kinke created dlang/phobos pull request #8633 "[stable] Fix Issue 22745 - std.parallelism.parallel fails to process empty range on a single CPU" fixing this issue: - Fix Issue 22745 - std.parallelism.parallel fails to process empty range on a single CPU https://github.com/dlang/phobos/pull/8633

dlang/phobos pull request #8633 "[stable] Fix Issue 22745 - std.parallelism.parallel fails to process empty range on a single CPU" was merged into stable: - ded657505ceec063163790b5c925ce31baca2b6f by Martin Kinkelin: Fix Issue 22745 - std.parallelism.parallel fails to process empty range on a single CPU https://github.com/dlang/phobos/pull/8633

dlang/phobos pull request #8650 "merge stable" was merged into master: - 5645d87eb165be79d49d54cd9ccdce921c5229a9 by Martin Kinkelin: Fix Issue 22745 - std.parallelism.parallel fails to process empty range on a single CPU https://github.com/dlang/phobos/pull/8650