PETSc version 3.17.4
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# PCQR

Uses a direct solver, based on QR factorization, as a preconditioner

### Notes

Usually this will compute an "exact" solution in one iteration and does not need a Krylov method (i.e. you can use -ksp_type preonly, or KSPSetType(ksp,KSPPREONLY) for the Krylov method

### See Also

PCCreate(), PCSetType(), PCType (for list of available types), PC,
PCILU, PCLU, PCCHOLESKY, PCICC, PCFactorSetReuseOrdering(), PCFactorSetReuseFill(), PCFactorGetMatrix(), PCFactorSetFill(), PCFactorSetUseInPlace(), PCFactorSetMatOrderingType(), PCFactorSetColumnPivot(), PCFactorSetPivotingInBlocks(),PCFactorSetShiftType(),PCFactorSetShiftAmount() PCFactorReorderForNonzeroDiagonal()

### Level

beginner

### Location

src/ksp/pc/impls/factor/qr/qr.c
Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages