[petsc-dev] Patch to fix vector allocation in ksp-fcg

[Barry Smith]

  When I added this change src/ksp/ksp/examples/tutorials/ex60 make runex60 failed with valgrind errors.

bsmith at es:/sandbox/bsmith/petsc/src/ksp/ksp/examples/tutorials$ /sandbox/bsmith/petsc/bin/petscmpiexec -valgrind -n 1 ./ex60 -ksp_monitor_short -ksp_rtol 1e-6 -diagfunc 1 -ksp_type fcg -ksp_fcg_mmax 1 -eta 0.1 
==14854== Invalid write of size 8
==14854==    at 0x5C32987: KSPAllocateVectors_FCG (fcg.c:37)
==14854==    by 0x5C32FE2: KSPSetUp_FCG (fcg.c:77)
==14854==    by 0x5BEBD69: KSPSetUp (itfunc.c:267)
==14854==    by 0x5BED3E3: KSPSolve (itfunc.c:419)
==14854==    by 0x403599: main (ex60.c:219)
==14854==  Address 0xa49f720 is 0 bytes after a block of size 16 alloc'd
==14854==    at 0x4C29BE8: memalign (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==14854==    by 0x4F33A45: PetscMallocAlign (mal.c:27)
==14854==    by 0x5C32D96: KSPSetUp_FCG (fcg.c:63)
==14854==    by 0x5BEBD69: KSPSetUp (itfunc.c:267)
==14854==    by 0x5BED3E3: KSPSolve (itfunc.c:419)
==14854==    by 0x403599: main (ex60.c:219)
==14854== 

Thus I have removed this change.

  Barry

> On Dec 19, 2014, at 8:18 AM, Sascha Schnepp <mail at saschaschnepp.net> wrote:
> 
> Hello developers,
> 
> I prepared a patch to fix the allocation of direction vectors in
> KSPAllocateVectors_FCG within ksp-fcg.
> 
> The fix consists only of replacing a PetscMin with a PetscMax. This
> prevents vectors being allocated one-by-one instead of chunksize
> of them once the preallocated ones (nprealloc) are exhausted.
> 
> Let me know if you prefer a PR.
> 
> Best,
> Sascha
> 
> 
> 
> --------------------------------------
> ETH Zurich
> Sascha Schnepp
> Institute of Geophysics - Geophysical Fluid Dynamics
> NO H23, Sonneggstrasse 5, 8092 Zurich, Switzerland
>  
> schnepps at ethz.ch
> www.gfd.ethz.ch; www.saschaschnepp.net
> 
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> <Fix-to-KSPAllocateVectors_FCG.patch>