So we can just take the advice out of the manual about setting this, since it's the default behavior? https://gitlab.com/petsc/petsc/-/merge_requests/3344
> Am 13.10.2020 um 16:41 schrieb Barry Smith <bsm...@petsc.dev>: > > > You only need to provide one of the options. > > The docs are slightly misleading.The flags only tells the matrix what to > do with new nonzero locations, preventing new ones. The Mat actually tracks > if new non-zeros locations are actually entered independent of the flags. So, > for example even if you did not supply any new flags AND your code did not > insert new locations then the structure would be reused. > > Barry > >> On Oct 13, 2020, at 7:47 AM, Thibaut Appel <t.appe...@imperial.ac.uk >> <mailto:t.appe...@imperial.ac.uk>> wrote: >> >> Hi there, just a quick question: >> >> It seems MAT_NEW_NONZERO_LOCATION_ERR set to PETSC_TRUE has kind of the same >> purpose as MAT_NEW_NONZERO_LOCATIONS set to PETSC_FALSE, the difference >> being if an additional entry is there, the former produces an error whereas >> in the latter it is simply ignored. >> >> However the manual states: >> >> 'If one wishes to repeatedly assemble matrices that retain the same nonzero >> pattern (such as within a nonlinear or time-dependent problem), the option >> MatSetOption(MatA,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE); should be >> specified after the first matrix has been fully assembled. This option >> ensures that certain data structures and communication information will be >> reused (instead of regenerated) during successive steps, thereby increasing >> efficiency' >> >> If I only declare: >> >> CALL MatSetOption(MatA,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE,ierr) >> >> Would the data structures still be reused in later matrix assemblies? >> >> Or does it rather make sense to use conjointly: >> >> CALL MatSetOption(MatA,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE,ierr) >> CALL MatSetOption(MatA,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE,ierr) >> >> Thank you, >> >> >> >> Thibaut >> >
