The FAQ mentions PCNN, but the advice "-pc_type nn" is completely inadequate to actually use this method, and the referenced example does not exist. I have removed it's mention from the "Domain Decomposition" answer, I think it needs a working example in order to be mentioned there. Also, ex2 -pc_type nn -mat_type fails with a seg-fault, I haven't investigated why.
Barry, PCEXOTIC does have a working example, should it be mentioned here, or do you consider it to be a toy that users needn't bother trying to use. As for future DD directions, have you thought about what is necessary to provide quasi-generic support for optimized Schwarz. I was only vaguely aware of this method until recently, but this approach seems to offer significant potential, especially for some indefinite problems. Jed
