On Tue, 10 Jul 2007, Satish Balay wrote: > On Tue, 10 Jul 2007, Brian Biskeborn wrote: > > > > > Hello, > > > > Does anyone here have experience with using Petsc on a Blue Gene system? > > I'm at IBM's Almaden Research Center and am currently involved in porting > > some code that uses Petsc to Blue Gene. I've managed to compile and run > > the code, and it seems to produce the correct results, but it generates > > many floating point alignment exceptions at runtime. > > Can you send a log of these messages? Is this on BGL or BGP? Does the > program abort? [on encountering these messages] > > With the minimal runs I've done on BGL - I don't remember seing any > such messages. > > > I traced some of these warnings to a call to MatAssemblyBegin, so > > I'm thinking maybe the problem is in Petsc. The Blue Gene > > architecture requires 8- or 16-byte memory alignment for floating > > point operations, depending on whether they are issued in parallel, > > so I tried bumping up the alignment value in > > src/sys/src/memory/mal.c. This had no effect on the problem. > > [Barry can confirm this] the code in mal.c attempts to make sure the > memory allocated by PETSc is aligned properly. [8 byte boundary for > doubles] > > One possibility is that the data passed in to MatAssemblyBegin() is > not aligned?
Sorry - I meant to say MatSetValues().. Satish > > Satish > > > I didn't write any of the code I'm porting, and I'm not too familiar with > > it yet, so I suppose the problem could really be anywhere. My question > > here is simply this: has anyone seen this problem? Does it sound like an > > issue with Petsc, or is it more likely to be in the top-level code? > > > > Thanks, and best regards, > > Brian > > > > > >
