Re: [Patch, fortran] PR37336 finalization

[Paul Richard Thomas <paul.richard.thomas@gmail.com>]

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Hi All,

I am awaiting a green light to commit this patch.... or not.

Cheers

Paul


On Fri, 10 Mar 2023 at 16:49, Paul Richard Thomas <
paul.richard.thomas@gmail.com> wrote:

> Hi Thomas,
>
> Before answering that, I thought that I had better try the polyhedron
> suite with -fwrapv and -std=legacy together. As far as I can see, all is
> well and so, yes, I think that is a good idea.
>
> Cheers
>
> Paul
>
>
> ================================================================================
> Date & Time     :  9 Mar 2023 18:13:04
> Test Name       : gfor_13
> Compile Command : gfc13 -ffast-math -funroll-loops -O3 -fwrapv -std=legacy
> %n.f90 -o %n
> Benchmarks      : ac aermod air capacita channel2 doduc gas_dyn2 fatigue2
> induct2 linpk mp_prop_design nf protein rnflow test_fpu2 tfft2
> Maximum Times   :    10000.0
> Target Error %  :      0.100
> Minimum Repeats :     1
> Maximum Repeats :     2
>
>    Benchmark   Compile  Executable   Ave Run  Number   Estim
>         Name    (secs)     (bytes)    (secs) Repeats   Err %
>    ---------   -------  ----------   ------- -------  ------
>           ac      0.00       55904      7.17       2  0.0628
>       aermod      0.00     1280104     10.77       2  1.2769
>          air      0.00      136392      4.09       2  0.4276
>     capacita      0.00      102680     23.79       2  0.7587
>     channel2      0.00       43928    108.59       2  0.5834
>        doduc      0.00      194224     13.98       2  0.2468
>     gas_dyn2      0.00      104080    105.46       2  0.1659
>     fatigue2      0.00       90752     62.86       2  1.3092
>      induct2      0.00      224920     58.08       2  0.6594
>        linpk      0.00       51768      7.15       2  0.4892
> mp_prop_desi      0.00       48432     94.28       2  0.0164
>           nf      0.00       64480     11.16       2  0.0134
>      protein      0.00      140592     24.22       2 10.0347
>       rnflow      0.00      197704     20.74       2  0.1904
>    test_fpu2      0.00      147232     53.54       2  0.1093
>        tfft2      0.00       43896     55.09       2  3.8688
>
> Geometric Mean Execution Time =      26.19 seconds
>
>
> ================================================================================
>
> On Thu, 9 Mar 2023 at 17:30, Thomas Koenig <tkoenig@netcologne.de> wrote:
>
>> Hi Paul,
>>
>>
>> > -fdefault-integer-8 does indeed fix the problem with
>> > rnflow.f90 but breaks tfft2.f90, with a type mismatch at lines 36 and
>> 44.
>> >
>> >        integer(8), parameter   :: jmul =  843314861  ! multiplicateur
>> >        integer(8), parameter   :: jadd =  453816693  ! constante
>> additive
>> > Does the job and is portable.
>> >
>>
>> I think -frwapv (as suggested by Jakub) would be the better choice.
>> The problem is the linear congruential pseudo-random number generators
>> which were much used in earlier times (and are still present in
>> legacy code), which violate the Fortran standards by assuming silent
>> truncation.
>>
>> If a new optimization breaks this (widespread, but illegal) idiom,
>> maybe the best way to deal with it is to add -frwapv to -std=legacy.
>>
>> What do you think?
>>
>> Best regards
>>
>>         Thomas
>>
>
>
> --
> "If you can't explain it simply, you don't understand it well enough" -
> Albert Einstein
>


-- 
"If you can't explain it simply, you don't understand it well enough" -
Albert Einstein