On Wed, Aug 14, 2019 at 3:37 PM Jed Brown <j...@jedbrown.org> wrote: > Mark Adams via petsc-dev <petsc-dev@mcs.anl.gov> writes: > > > On Wed, Aug 14, 2019 at 2:35 PM Smith, Barry F. <bsm...@mcs.anl.gov> > wrote: > > > >> > >> Mark, > >> > >> Would you be able to make one run using single precision? Just single > >> everywhere since that is all we support currently? > >> > >> > > Experience in engineering at least is single does not work for FE > > elasticity. I have tried it many years ago and have heard this from > others. > > This problem is pretty simple other than using Q2. I suppose I could try > > it, but just be aware the FE people might say that single sucks. > > When they say that single sucks, is it for the definition of the > operator or the preconditioner? >
Operator. And "ve seen GMRES stagnate when using single in communication in parallel Gauss-Seidel. Roundoff is nonlinear. > > As point of reference, we can apply Q2 elasticity operators in double > precision at nearly a billion dofs/second per GPU. > I'm skeptical of big wins in preconditioning (especially setup) due to > the cost and irregularity of indexing being large compared to the > bandwidth cost of the floating point values. >
