[petsc-users] PETSc with modern C++

[Jed Brown]

Matthew Knepley <knepley at gmail.com> writes:

> On Tue, Apr 4, 2017 at 10:02 PM, Jed Brown <jed at jedbrown.org> wrote:
>
>> Matthew Knepley <knepley at gmail.com> writes:
>>
>> > On Tue, Apr 4, 2017 at 3:40 PM, Filippo Leonardi <filippo.leon at gmail.com
>> >
>> > wrote:
>> >
>> >> I had weird issues where gcc (that I am using for my tests right now)
>> >> wasn't vectorising properly (even enabling all flags, from
>> tree-vectorize,
>> >> to mavx). According to my tests, I know the Intel compiler was a bit
>> better
>> >> at that.
>> >>
>> >
>> > We are definitely at the mercy of the compiler for this. Maybe Jed has an
>> > idea why its not vectorizing.
>>
>> Is this so bad?
>>
>> 000000000024080e <VecMAXPY_Seq+0x2fe> mov    rax,QWORD PTR [rbp-0xb0]
>> 0000000000240815 <VecMAXPY_Seq+0x305> add    ebx,0x1
>> 0000000000240818 <VecMAXPY_Seq+0x308> vmulpd ymm0,ymm7,YMMWORD PTR
>> [rax+r9*1]
>> 000000000024081e <VecMAXPY_Seq+0x30e> mov    rax,QWORD PTR [rbp-0xa8]
>> 0000000000240825 <VecMAXPY_Seq+0x315> vfmadd231pd ymm0,ymm8,YMMWORD PTR
>> [rax+r9*1]
>> 000000000024082b <VecMAXPY_Seq+0x31b> mov    rax,QWORD PTR [rbp-0xb8]
>> 0000000000240832 <VecMAXPY_Seq+0x322> vfmadd231pd ymm0,ymm6,YMMWORD PTR
>> [rax+r9*1]
>> 0000000000240838 <VecMAXPY_Seq+0x328> vfmadd231pd ymm0,ymm5,YMMWORD PTR
>> [r10+r9*1]
>> 000000000024083e <VecMAXPY_Seq+0x32e> vaddpd ymm0,ymm0,YMMWORD PTR
>> [r11+r9*1]
>> 0000000000240844 <VecMAXPY_Seq+0x334> vmovapd YMMWORD PTR [r11+r9*1],ymm0
>> 000000000024084a <VecMAXPY_Seq+0x33a> add    r9,0x20
>> 000000000024084e <VecMAXPY_Seq+0x33e> cmp    DWORD PTR [rbp-0xa0],ebx
>> 0000000000240854 <VecMAXPY_Seq+0x344> ja     000000000024080e
>> <VecMAXPY_Seq+0x2fe>
>>
>
> I agree that is what we should see. It cannot be what Fillippo has if he is
> getting ~4x with the template stuff.

I'm using gcc.  Fillippo, can you make an easy to run test that we can
evaluate on Xeon and KNL?
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