[petsc-users] Question - about the 'Hint for performance tuning'

[김성익]

After reconfigure by
./arch-main-debug/lib/petsc/conf/reconfigure-arch-main-debug.py
--with-debugging=0 --PETSC_ARCH=arch-main-opt ,
I tried to build my code.

But I got an error as below
[image: image.png]
How can I fix this?




2023년 1월 3일 (화) 오전 4:05, Barry Smith <bsmith at petsc.dev>님이 작성:

>
>
> On Jan 2, 2023, at 9:27 AM, 김성익 <ksi2443 at gmail.com> wrote:
>
> There are more questions.
>
> 1. Following your comments, but there is an error as below.
> <image.png>
> How can I fix this?
>
>
>    The previous value of PETSC_ARCH was not arch-main-debug do ls
> $PETSC_DIR and locate the directory whose name begins with arch- that will
> tell you the previous value used for PETSC_ARCH.
>
>
> 2. After changing the optimized build, then how can I set the debug mode
> again?
>
>
>    export PETSC_ARCH=arch- whatever the previous value was and then
> recompile your code (note you do not need to recompile PETSc just your
> executable).
>
>
> 3.Following your comments, the new makefile is as below. Is it right?
> CFLAGS       = -O3
> FFLAGS       =
> CPPFLAGS         =
> FPPFLAGS         =
> COPTFLAGS        = -march=native
>
>
> app : a1.o a2.o a3.o a4.o
>    $(LINK.C) -o $@ $^ $(LDLIBS)
>
>
> include ${PETSC_DIR}/lib/petsc/conf/rules
> include ${PETSC_DIR}/lib/petsc/conf/test
>
>
> Best not to set these values in the makefile at all because they will
> affect all compilers. Just set them with ./configure CCOPTFLAGS="-O3
> -march=native"
>
>
>
> 4. I have no such processors. Where can I find benchmark information about
> STREAMS?
>
>
>   do make mpistreams in PETSC_DIR
>
>
>
>
> Thanks,
> Hyung Kim
>
>
>
>
>
>
>
>
> 2023년 1월 2일 (월) 오후 11:03, Matthew Knepley <knepley at gmail.com>님이 작성:
>
>> On Mon, Jan 2, 2023 at 4:16 AM 김성익 <ksi2443 at gmail.com> wrote:
>>
>>> Hello,
>>>
>>> Happy new year!!
>>>
>>>
>>> I have some questions about “Hint for performance tuning” in user guide
>>> of petsc.
>>>
>>>
>>> 1.     In the “Performance Pitfalls and Advice” section, there are 2
>>> modes “debug” and “optimized builds. My current setup is debug mode. So I
>>> want to change for test the performance the optimized build mode. However,
>>> if I configure again, does the existing debug mode disappear? Is there any
>>> way to coexist the 2 modes and use them in the run the application?
>>>
>> Suppose your current arch is named "arch-main-debug". Then you can make
>> an optimized version using
>>
>>   cd $PETSC_DIR
>>   ./arch-main-debug/lib/petsc/conf/reconfigure-arch-main-debug.py
>> --with-debugging=0 --PETSC_ARCH=arch-main-opt
>>
>>
>>> 2.     In the guide, there are some paragraphs about optimization level
>>> of compiler. To control the optimization level of compiler, I put the ‘-O3’
>>> as below. Is this right??
>>> CFLAGS       = -O3
>>> FFLAGS       =
>>> CPPFLAGS         =
>>> FPPFLAGS         =
>>>
>>>
>>> app : a1.o a2.o a3.o a4.o
>>>    $(LINK.C) -o $@ $^ $(LDLIBS)
>>>
>>>
>>> include ${PETSC_DIR}/lib/petsc/conf/rules
>>> include ${PETSC_DIR}/lib/petsc/conf/test
>>>
>>
>> You could dp this, but that only changes it for that directory. It is
>> best to do it by reconfiguring.
>>
>>
>>> 3.     In the guide, user should put ‘-march=native’ for using AVX2 or
>>> AVX-512. Where should I put the ‘-march=native’ for using AVX?
>>>
>> You can add --COPTFLAGS="<user flags>" with any flags you want to the
>> configure.
>>
>> 4.     After read the “Hint for performance tuning” I understood that
>>> for good performance and scalability user should use the multiple node and
>>> multiple socket . However, before composing cluster system, many users just
>>> can use desktop system.
>>> In that case, between intel 13th i9 and amd ryzen 7950x, can the 7950x,
>>> which has an arichitecture similar to the server processor, be more
>>> suitable for petsc? (Because the architecture of intel desktop cpu is
>>> big.little.)
>>>
>>
>> A good guide is to run the STREAMS benchmark on the processor. PETSc
>> performance closely tracks that.
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>>
>>>
>>> Thanks,
>>>
>>> Hyung Kim
>>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>> https://www.cse.buffalo.edu/~knepley/
>> <http://www.cse.buffalo.edu/~knepley/>
>>
>
>
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