[CP2K:3930] dbcsr matrix help

[Urban Borštnik]

Hi,

for starters I would point you to the the src/dbcsr_lib directory of the
CP2K source code (pointers on how to get it are on
http://www.cp2k.org/).  Specifically, have a look at the
dbcsr_test_multiply.F file.

I see issues you want to solve.

One is to create a distribution from scratch.  If you don't care about
specific block sizes, then the two basic routines you will need are
create_bl_distribution and dbcsr_distribution_new, both found in
dbcsr_dist_operations.F.  You have to run the first one twice, once for
rows and another time for columns.  It returns two managed arrays: block
sizes and the the block distribution.  The block sizes array is a
sequential list of block sizes; the sum of these is equal to the number
of elements in your matrix row/column.  The block distribution array is
a mapping from the blocks to processor rows/columns.

The other issue is how to fill the array.  The dbcsr_make_random_matrix
in dbcsr_test_methods.F can serve as an example, or you can look at the
copy_fm_to_dbcsr subroutine in CP2K's cp_dbcsr_operations.F file (this
latter routine is used to convert a block-cyclic--distributed
ScaLAPACK-type matrix to DBCSR).  The way to go really depends on how
big your matrices are.  If it doesn't fit in memory on one computer,
then it gets a bit trickier

Best regards,
Urban.

On Thu, 2012-07-19 at 13:56 -0700, Adam wrote:
> Hi,
> 
> I'm a sophomore student at lanl, relatively new to fortran. I'm
> supposed find a way to square large sparse matrices in parallel. I
> found a way to do this with the dbcsr part of cp2k, I was wondering
> how you would go about setting the distribution of a dbcsr_matrix
> based on a square matrix you read in from a file (for example:
> REAL(8):: DATA(10, 10) ). 
> 
> Any help is greatly appreciated,
> Adam
> 
> 
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