• Per =?UTF-8?B?Tm9yZGzDtnc=?= (12/12) Jun 28 2019 According to
• kinke (2/5) Jun 28 2019 It's `-mcpu=native`.
• Per =?UTF-8?B?Tm9yZGzDtnc=?= (2/3) Jun 28 2019 Can/Could the value of this switch be detected at compile-time?
• Nicholas Wilson (8/11) Jun 28 2019 Well from the point of view of the code you usually don't really
• Johan Engelen (4/10) Jun 30 2019 Indeed:
• Per =?UTF-8?B?Tm9yZGzDtnc=?= (8/11) Jul 01 2019 Cool.
• Andrei Alexandrescu (5/23) Jul 04 2019 There are several schools of thought. A simple way to ease into it is to...
• a11e99z (3/6) Jun 30 2019 dynamic compilation may be useful too
• 9il (3/10) Jul 01 2019 Specializations are welcome for mir-algorithm.

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

According to

http://0x80.pl/notesen/2018-10-03-simd-index-of-min.html

SIMD-tuning a Phobos function, such as,

     std.algorithm.searching.minIndex

for an `int[]`-haystack on AVX512f leads to a speedup of 15x.

Should such specializations be added to Phobos or is such an 
optimization only possible for LDC or GCC but not for DMD?

Further, when will compilers, such as LDC and GDC, be able to do 
these auto-vectorizations automatically? Will the GCC and Clang 
compiler setting of `-march=native` play a role also for LDC in 
the future. Currently (in LDC 1.16.0) the setting `-march=native` 
is not allowed.

kinke <noone nowhere.com> writes:

On Friday, 28 June 2019 at 15:49:34 UTC, Per Nordlöw wrote:
 Will the GCC and Clang compiler setting of `-march=native` play 
 a role also for LDC in the future. Currently (in LDC 1.16.0) 
 the setting `-march=native` is not allowed.

It's `-mcpu=native`.

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

On Friday, 28 June 2019 at 16:30:31 UTC, kinke wrote:
 It's `-mcpu=native`.

Can/Could the value of this switch be detected at compile-time?

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Friday, 28 June 2019 at 19:53:10 UTC, Per Nordlöw wrote:
 On Friday, 28 June 2019 at 16:30:31 UTC, kinke wrote:
 It's `-mcpu=native`.

 Can/Could the value of this switch be detected at compile-time?

Well from the point of view of the code you usually don't really 
care because it's just like passing a higher value of n to `-On`.

It's probably already implemented as an LDC specific __trait, but 
if it isn't it shouldn't be too hard to add to 
__traits(getTargetInfo) (the optimiser values that -mcpu=native 
sets probably will be made available through getTargetInfo at 
some point though).

Johan Engelen <j j.nl> writes:

On Friday, 28 June 2019 at 22:53:45 UTC, Nicholas Wilson wrote:
 On Friday, 28 June 2019 at 19:53:10 UTC, Per Nordlöw wrote:
 On Friday, 28 June 2019 at 16:30:31 UTC, kinke wrote:
 It's `-mcpu=native`.

 Can/Could the value of this switch be detected at compile-time?

 It's probably already implemented as an LDC specific __trait,

Indeed:
https://wiki.dlang.org/LDC-specific_language_changes#targetCPU

-Johan

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

On Sunday, 30 June 2019 at 15:40:07 UTC, Johan Engelen wrote:
 Indeed:
 https://wiki.dlang.org/LDC-specific_language_changes#targetCPU

 -Johan

Cool.

Even better,

https://wiki.dlang.org/LDC-specific_language_changes#targetHasFeature

is _exactly_ what I want! :)

Still, the question remains to be answered:

     Where should these CPU-specialized overloads of Phobos 
algorithms be placed?

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 7/1/19 11:52 AM, Per Nordlöw wrote:
 On Sunday, 30 June 2019 at 15:40:07 UTC, Johan Engelen wrote:
 Indeed:
 https://wiki.dlang.org/LDC-specific_language_changes#targetCPU

 -Johan

 
 Cool.
 
 Even better,
 
 https://wiki.dlang.org/LDC-specific_language_changes#targetHasFeature
 
 is _exactly_ what I want! :)
 
 Still, the question remains to be answered:
 
      Where should these CPU-specialized overloads of Phobos algorithms 
 be placed?

There are several schools of thought. A simple way to ease into it is to 
place specializations with the algorithms. That's transparent to coders 
and backward compatible. The decision to create visible, user-selectable 
versions can be thus postponed.

a11e99z <black80 bk.ru> writes:

On Friday, 28 June 2019 at 19:53:10 UTC, Per Nordlöw wrote:
 On Friday, 28 June 2019 at 16:30:31 UTC, kinke wrote:
 It's `-mcpu=native`.

 Can/Could the value of this switch be detected at compile-time?

dynamic compilation may be useful too
https://forum.dlang.org/post/bskpxhrqyfkvaqzoospx forum.dlang.org

9il <ilyayaroshenko gmail.com> writes:

On Friday, 28 June 2019 at 15:49:34 UTC, Per Nordlöw wrote:
 According to

 http://0x80.pl/notesen/2018-10-03-simd-index-of-min.html

 SIMD-tuning a Phobos function, such as,

     std.algorithm.searching.minIndex

 for an `int[]`-haystack on AVX512f leads to a speedup of 15x.

 Should such specializations be added to Phobos or is such an 
 optimization only possible for LDC or GCC but not for DMD?

Specializations are welcome for mir-algorithm.

http://mir-algorithm.libmir.org/mir_algorithm_iteration.html