Where is BLACS in the MKL?

[schmmd]

I am trying to use BLACS from Visual Studio to use ScaLapack functions. However, I cannot find the blacs functions anywhere in the header files. They do exist in the DLLs, however. How am I supposed to call them from C/C++?

[ArturGuzik]

Quoting - schmmd

I am trying to use BLACS from Visual Studio to use ScaLapack functions. However, I cannot find the blacs functions anywhere in the header files. They do exist in the DLLs, however. How am I supposed to call them from C/C++?

I don't entirely understand what you're trying to do but you'll get CBLAS by linking to mkl_core.lib. You will find header file(s) in include folder.

The word of warning, be aware that CBLAS is C interface to BLAS (written in FORTRAN) so you'll have some issues to resolve/address.


A.

[sathya_]

schmmd,

Assuming you are talking about CBLAS,

• the header file is mkl_cblas.h

• You can either call the FORTRAN functions directly from C/C++ (or) use the C interface functions provided in CBLAS to call the functions. I personally find the C interface functions easier to call, but the FORTRAN interfaces also work when called directly from C/C++.

What functions are you trying to call?

[Todd_R_Intel]

Quoting - schmmd

I am trying to use BLACS from Visual Studio to use ScaLapack functions.

Most people use ScaLAPACK and the use of BLACS underneath is largely invisible to them. I don't think I've heard a request for BLACS headers , but we have documented them in our reference manual now, so it would seem natural to have the headers. I'll see what I can find.

-Todd

[Customer__Intel4]

Hi Todd

After 2.5 years of your reply, I still can't find any c interface to the BLACS in the MKL refrence manual ? For some one who wants to use PBLAS, in c++ using MKL, does CBLACS exist in MKL or not?

Tarek

[Todd_R_Intel]

Hello Tarek,

After 2.5 years, we have included a C header file (mkl_blacs.h)which should make it easier to directly use the BLACS from C++. We don't have a C interface, so you'll need to make the necessary adjustments for calling functions written in Fortran. The header file might help you.

Is there a particular BLACS function that interests you? WhycallBLACS functions from your app for communication rather than using MPI?

Todd

[Customer__Intel4]

Quoting Todd Rosenquist (Intel)

WhycallBLACS functions from your app for communication rather than using MPI?

Todd

Thanks Todd for the reply,

you mean that I can use normal MPI functions with PBLAS instead of BLACS functions?

[Todd_R_Intel]

Tarek, Here's what I mean:

It sounds like you have a C++ application and you want to use PBLAS. Everything should work just fine for you to do so without even considering the question of the existence of the BLACS for the C++ user. The BLACS are there in Intel MKLand the PBLAS that are in Intel MKL should call them correctly without any direct interaction with your C++ application. In my (somewhat limited) experience I haven't seen people using the BLACS directly (from C++ or Fortran).

Now if you do need some communication in your application---outside of, or in support of your use of the PBLAS---then we'd expect you to use MPI communication functions rather than using the BLACS.

But, if I've missed something let us know a little more about your direct use of theBLACS.

Todd