[petsc-dev] Uninitialized memory used in MatLUFactorNumeric_SeqAIJ_Inode?

[Chetan Jhurani]

Hello, 

I noticed a big difference between debug and optimized versions 
of petsc3.1-p2 while using KSPSolve with PCILU and GMRES. 

This is on Windows/VS2005 if it matters. 

Well, luckily, the big difference was convergence in optimized 
version vs. no convergence in debug version for some problems 
so it could not be dismissed as just a floating point issue.

It seems the problem happens in MatLUFactorNumeric_SeqAIJ_Inode 
in src/mat/impls/aij/seq/inode.c because it reads from b->a which 
is pointing to the non-zeroed array elements of the output 
factor B.  This specific b->a points to memory allocated in 
MatILUFactorSymbolic_SeqAIJ, src/mat/impls/aij/seq/aijfact.c 
by PetscMalloc((bdiag[0]+1)*sizeof(PetscScalar),&b->a); 

Using a PetscMemzero(b->a,(bdiag[0]+1)*sizeof(PetscScalar)) 
after the allocation makes the debug vs. optimized problem 
go away completely. 

Can someone confirm this?  Is there a better fix? 

Thanks, 

Chetan