[firedrake] operations on matrices

[Lawrence Mitchell]

On 5 Jan 2015, at 09:39, David Ham <David.Ham at imperial.ac.uk> wrote:

> 
> 
> On 5 January 2015 at 09:37, Cotter, Colin J <colin.cotter at imperial.ac.uk> wrote:
> Oh yes, good isolation of the problem.
> 
> If alpha also depends on values of A, do we have a problem there too?
> 
> 
> Yes. Same problem. There is no current way for a parallel loop to read the entries of a matrix.

You could do this by creating a new output matrix, looping over the rows of the input matrix:

out = A.duplicate()

start, end = A.getOwnershipRange()

for row in range(start, end):
   acol, aval = A.getRow(row)
   alphacol, alphaval = alpha.getRow(row)
   assert all(acol == alphacol), "Column pattern must match"
   val = aval * alphaval
   out.setValues(row, acol, val, addv=PETSc.InsertMode.INSERT_VALUES)

out.assemble()

Completely untested.

Lawrence

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 455 bytes
Desc: Message signed with OpenPGP using GPGMail
URL: <http://mailman.ic.ac.uk/pipermail/firedrake/attachments/20150105/4cf6132b/attachment.sig>