Building an optimized OpenBLAS packages

[Yuan Xu]

Hi all,

I am new to OpenBLAS, thanks for the wonderful package.

I have a ubuntu system (Intel Core i7), and tried openblas from debian package, it is really fast.

Then I download the source code from git, and build the library with 'make', the resulted library is libopenblas_sandybridgep-r0.2.8.so

it detects my CPU correctly, but according to my test, it is slower than the one from debian package.

Did I miss some option for building optimized OpenBLAS?

Thanks!

PS:

* the openblas from debian package is version 0.2.6 (it claimed to switch kernels according to running architecture)

* my test is here: https://github.com/xuyuan/blas_call_benchmark

[Zhang Xianyi]

Thank you for using OpenBLAS

Did you just test dot?

Xianyi

2013/12/12 Yuan Xu <xuyu...@gmail.com>

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[Yuan Xu]

Yes, only dot

[Yuan Xu]

Hi Xianyi,

Thanks for your reply.

After limiting the number of threads to 1, both versions perform the same.

When setting the number of threads to 4, the debian packaged version gets improved, however the locally compiled version performs the same as before.

the output of 'make' is:

 OpenBLAS build complete.

  OS               ... Linux             

  Architecture     ... x86_64               

  BINARY           ... 64bit                 

  C compiler       ... GCC  (command line : gcc)

  Fortran compiler ... GFORTRAN  (command line : gfortran)

  Library Name     ... libopenblas_sandybridgep-r0.2.8.a (Multi threaded; Max num-threads is 4)

so, what do I miss?

Best Regards,

Xu, Yuan

On Thu, Dec 12, 2013 at 1:53 PM, Zhang Xianyi <traits...@gmail.com> wrote:

please set the environment before your test.

export OPENBLAS_NUM_THREADS=1

2013/12/12 Yuan Xu <xuyu...@gmail.com>

[Carter Schonwald]

Could it be something like having MPI enabled or not?

[Yuan Xu]

How do I enable/disable MPI? thanks!

Best Regards,

Xu, Yuan

[Zhang Xianyi]

2013/12/13 Yuan Xu <xuyu...@gmail.com>

Hi Xianyi,

Thanks for your reply.

After limiting the number of threads to 1, both versions perform the same.

When setting the number of threads to 4, the debian packaged version gets improved, however the locally compiled version performs the same as before.

Sorry, I have no idea about debian packaged version.

 

the output of 'make' is:

 OpenBLAS build complete.

  OS               ... Linux             

  Architecture     ... x86_64               

  BINARY           ... 64bit                 

  C compiler       ... GCC  (command line : gcc)

  Fortran compiler ... GFORTRAN  (command line : gfortran)

  Library Name     ... libopenblas_sandybridgep-r0.2.8.a (Multi threaded; Max num-threads is 4)

It looks fine.

[Zhang Xianyi]

What do you mean enable/disable MPI?

You can `make USE_THREAD=0` to build single thread library.

On runtime, you can call `void openblas_set_num_threads(int num_threads);`.

2013/12/15 Yuan Xu <xuyu...@gmail.com>

[Yuan Xu]

When the number of threads is changed from 1 to 4, the performance should be better in a i7 CPU, right?

It wasn't in my test, but the precompiled debian version gets better as expected.

Now my question is, does building with just 'make' command (without any optional flag) result optimized binary?

Thanks!

Best Regards,

Xu, Yuan

[Zhang Xianyi]

2013/12/16 Yuan Xu <xuyu...@gmail.com>

When the number of threads is changed from 1 to 4, the performance should be better in a i7 CPU, right?

It wasn't in my test, but the precompiled debian version gets better as expected.

Now my question is, does building with just 'make' command (without any optional flag) result optimized binary?

Yes, by default 'make ' is optimized.