PETSc version 3.16.5
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# KSPCGS

This code implements the CGS (Conjugate Gradient Squared) method.

### Options Database Keys

| see KSPSolve()

### References

| 1. | - Sonneveld, 1989.

### Notes

Does not require a symmetric matrix. Does not apply transpose of the matrix. Supports left and right preconditioning, but not symmetric.

### Developer Notes

Has this weird support for doing the convergence test with the natural norm, I assume this works only with no preconditioning and symmetric positive definite operator.

### See Also

KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS, KSPSetPCSide()

### Level

beginner

### Location

src/ksp/ksp/impls/cgs/cgs.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages