That should be alpha = 1/(1 + v' w) and you need only store the product alpha * w Jed -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 197 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20081014/b10b3e17/attachment.pgp>