llvm dev - May 2017 - PSA: Parallel STL algorithms available in LLVM

Hi all,

This is just a PSA that as of r302752, 3 parallel algorithms (for_each,
for_each_n, and sort) are available in llvm/Support/Parallel.h.

Effort was made to match the C++ Parallelism TS N4507 [
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4507.pdf] as
closely as possible, but some aspects were intentionally omitted.

No support is added for the executor proposal N4406 [
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4406.pdf], but I
plan to try to work on this in the future, with no specified timeline.
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The spec doesn't seem to say anything about recursive calls to parallel
functions.  In my mind that means the functions must support it, since it
doesn't explicitly say it does not need to support it.  Do you think
that's
accurate?

If so, I'll rely on that behavior in LLDB, and extend the implementation in
LLVM accordingly.

On Wed, May 10, 2017 at 5:37 PM, Zachary Turner via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi all,
>
> This is just a PSA that as of r302752, 3 parallel algorithms (for_each,
> for_each_n, and sort) are available in llvm/Support/Parallel.h.
>
> Effort was made to match the C++ Parallelism TS N4507 [
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4507.pdf] as
> closely as possible, but some aspects were intentionally omitted.
>
> No support is added for the executor proposal N4406 [
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4406.pdf], but I
> plan to try to work on this in the future, with no specified timeline.
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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It's hard to say.  By definition it appears undefined (in the sense that
the TS literally does not define it), but on the other hand it is a TS and
this issue would (hopefully) come up and be specified before it made it to
standardization.

Supporting recursive parallel calls certainly seems like desirable
behavior, so from my point of view it would be nice to make sure it works.
Not sure if others feel differently.

On Wed, May 10, 2017 at 8:08 PM Scott Smith <scott.smith at
purestorage.com>
wrote:
> The spec doesn't seem to say anything about recursive calls to parallel
> functions.  In my mind that means the functions must support it, since it
> doesn't explicitly say it does not need to support it.  Do you think
that's
> accurate?
>
> If so, I'll rely on that behavior in LLDB, and extend the
implementation
> in LLVM accordingly.
>
> On Wed, May 10, 2017 at 5:37 PM, Zachary Turner via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi all,
>>
>> This is just a PSA that as of r302752, 3 parallel algorithms (for_each,
>> for_each_n, and sort) are available in llvm/Support/Parallel.h.
>>
>> Effort was made to match the C++ Parallelism TS N4507 [
>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4507.pdf] as
>> closely as possible, but some aspects were intentionally omitted.
>>
>> No support is added for the executor proposal N4406 [
>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4406.pdf], but
>> I plan to try to work on this in the future, with no specified
timeline.
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>
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