[petsc-users] consistence of PETSC/SLEPC with MPI, BLACS, SCALAPACK calls...

[Giacomo Mulas]

On Mon, 27 Nov 2017, Jose E. Roman wrote:

> You have PetscInt, PetscBLASInt and PetscMPIInt.

I will try to work my way through it. In most cases it looks very clear.
There are some borderline cases in which things are not so clearly cut
though.
I.e. if I call Cblacs_get( -1, 0, &ictxt ) to get a context, I would guess
that the context should be PetscMPIInt even if I get it via a blacs call.
Similarly for Cblacs_gridinit() or Cblacs_gridinfo() they all deal with
strictly MPI stuff so I bet they should all get and return PetscMPIInt
variables. On the other hand, if I use 
lnr = numroc_(&n, &nbr, &myrow, &ione, &nprows);
to get the number of rows (in this case) locally allocated to a distributed
blacs array, I would bet that lnr, n, nbr, ione should be PetscBlasInt and
myrow, nprows should be PetscMPIInt. 
Would anyone proficient with both blacs/scalapack and petsc care to confirm
or correct if wrong? Possibly just pointing me to where to look to find the
answers without bothering him/her further?

Thanks
Giacomo

>
>> El 27 nov 2017, a las 10:12, Giacomo Mulas <gmulas at oa-cagliari.inaf.it> escribió:
>>
>> Hello.
>>
>> I am using, within the same C code, both SLEPC/PETSC and Scalapack/Blacs. On the big parallel machine on which I do production runs, I compiled
>> SLEPC/PETSC with the "--known-64-bit-blas-indices" and
>> "--with-64-bit-indices" options, linking them with the ilp64 version of the
>> Intel MKL libraries, while on the workstation on which I do the development
>> I use the standard libraries provided by the (debian, in my case) packaging
>> system.  For Slepc/Petsc themselves I just use the PETSC data types and this
>> automagically defines integers of the appropriate size on both machines.
>>
>> However, when using BLACS, Scalapack and MPI directly in the same code, I
>> will obviously need to use consistent function definitions for them as well. Do I need to set up some complicated independent #ifdef machinery for this
>> or are there some appropriate PETSC data types that I can use that will
>> ensure this consistency?  Of course I am including slepc/petsc include
>> files, so all PETSC data types are defined according to the local
>> PETSC/SLEPC options.  Can some PETSC developer give me some hint on how to
>> make my MPI, BLACS, SCALAPACK (and PBLAS etc.) calls clean and consistent
>> with this? Perhaps even referring to some examples in the PETSC source code
>> that I can read and take as a reference for this.
>>
>> Thanks in advance
>> Giacomo
>>
>> --
>> _________________________________________________________________
>>
>> Giacomo Mulas <gmulas at oa-cagliari.inaf.it>
>> _________________________________________________________________
>>
>> INAF - Osservatorio Astronomico di Cagliari
>> via della scienza 5 - 09047 Selargius (CA)
>>
>> tel.   +39 070 71180255
>> mob. : +39 329  6603810
>> _________________________________________________________________
>>
>> "When the storms are raging around you, stay right where you are"
>>                         (Freddy Mercury)
>> _________________________________________________________________
>
>

-- 
_________________________________________________________________

Giacomo Mulas <gmulas at oa-cagliari.inaf.it>
_________________________________________________________________

INAF - Osservatorio Astronomico di Cagliari
via della scienza 5 - 09047 Selargius (CA)

tel.   +39 070 71180255
mob. : +39 329  6603810
_________________________________________________________________

"When the storms are raging around you, stay right where you are"
                          (Freddy Mercury)
_________________________________________________________________