[Trilinos-Users] VbrMatrix RAM usage

[Andrea Zonca]

Thanks David,

On Tue, Mar 1, 2011 at 11:23, David Cole <david.cole at kitware.com> wrote:
> Which OS and compiler are you using? Are you building a Debug or Release build?

I am now debugging locally with Ubuntu 10.04, gcc 4.4.5, building just with:

g++ testVBR.cpp -ltrilinos_epetra -ltrilinos_aztecoo
-ltrilinos_teuchos -I/usr/include/trilinos/ -I/usr/include/openmpi -o
testVBR && mpirun -n 2 ./testVBR

but I found initially anomalous ram usage on Hopper with PGI compiler.

> The per-allocation overhead of a Debug build with Microsoft Visual
> Studio is near 40 bytes per allocation because of memory tracking
> debug allocator data structures.
>
> Is each row a separate allocation, or is there a contiguous block of
> doubles in the internals of this code?

each row is separate, see:
https://gist.github.com/848310
P is a block matrix, each blockrow of the matrix has a (1x3) block matrix.
for testing I am just inserting everything in the first blockcolumn.
After building the matrix, I fillcomplete against PixMax which is a
linear blockmap of 3 elements.
So at the end I have a matrix of 1e6x1e7 where only 1e6 block elements
(so 3e6 doubles) are nonzero.

thanks,
andrea zonca