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

[Sascha Schnepp]

Hello,

yes, I am sorry, there was a bug in the patch.

The problem occurred when the number of preallocated vectors was bigger than the max number of old directions to store - as in the options in runex60. It hadn’t checked this case. Again, sorry for that.

I prepared a new patch which also replaces a PetscMin for a PetscMax but also swaps argument positions. I ran ex2, ex43 and ex60 with appropriate options in valgrind and got no errors.

BTW:
valgrind is available for Mac through MacPorts again.

 Sascha


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On 20 Dec 2014, at 18:17, Barry Smith <bsmith at mcs.anl.gov> wrote:

> 
>  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
>> 
>> +41 44 632 0244 phone
>> 
>> Consider encrypting your mail
>> Public Key ID: 0x67AC24EF
>> --------------------------------------
>> 
>> <Fix-to-KSPAllocateVectors_FCG.patch>
>