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Hot fix for equal algo
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Authored by MikeDvorskiy on Mar 22 2019, 10:09 AM.

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rL LLVM

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MikeDvorskiy created this revision.Mar 22 2019, 10:09 AM
ldionne requested changes to this revision.Mar 22 2019, 10:44 AM
ldionne added inline comments.
include/pstl/internal/glue_algorithm_impl.h
739 ↗(On Diff #191905)

Please restore the space here.

739 ↗(On Diff #191905)

Why are you removing the TODO?

750 ↗(On Diff #191905)

What problem is this fixing? IIUC, before this patch, we would end up calling equal(_ExecutionPolicy&&, _ForwardIterator1, _ForwardIterator1, _ForwardIterator2) here and that would be a compiler error because __pstl::internal::pstl_equal() is not an iterator. Is that correct?

If so, this change should be accompanied by a test that goes through this code path.

This revision now requires changes to proceed.Mar 22 2019, 10:44 AM
MikeDvorskiy marked an inline comment as done.Mar 25 2019, 2:06 AM
MikeDvorskiy added inline comments.
include/pstl/internal/glue_algorithm_impl.h
750 ↗(On Diff #191905)

No...
The fact is there is several version of std::equal..
In particular,
equal(_ExecutionPolicy&&, _ForwardIterator1, _ForwardIterator1, _ForwardIterator2...
and
equal(_ExecutionPolicy&&, _ForwardIterator1, _ForwardIterator1, _ForwardIterator2, _ForwardIterator2...
where each sequence has its own length.
So, the error was the code calls the first version with "first1, last1, __first2"

MikeDvorskiy marked an inline comment as done.Mar 25 2019, 3:27 AM
MikeDvorskiy added inline comments.
include/pstl/internal/glue_algorithm_impl.h
739 ↗(On Diff #191905)

"Distance check" is a kind of optimization for random access iterators..
But for forward iterators it is a kind of overhead.. and we should keep TODO complete the fixing.

Furthermore, I've just noticed, in case of size equal, we call a serial version std::equal(first1, last1, first2, p);

Ok, I'll complete the fixing and update the patch.
(and extend the test coverage as well)

ldionne accepted this revision.Mar 25 2019, 5:31 AM
This revision is now accepted and ready to land.Mar 25 2019, 5:31 AM
ldionne added inline comments.Mar 25 2019, 5:37 AM
include/pstl/internal/glue_algorithm_impl.h
739 ↗(On Diff #191905)

Please fix this in a separate patch (I've already applied this one).

This revision was automatically updated to reflect the committed changes.
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