# KSPPIPECR
Pipelined conjugate residual method. [](sec_pipelineksp) 


## Notes
This method has only a single non-blocking reduction per iteration, compared to 2 blocking for standard `KSPCR`.  The
non-blocking reduction is overlapped by the matrix-vector product, but not the preconditioner application.

See also `KSPPIPECG`, where the reduction is only overlapped with the matrix-vector product.

MPI configuration may be necessary for reductions to make asynchronous progress, which is important for performance of pipelined methods.
See [](doc_faq_pipelined)


## Contributed by
Pieter Ghysels, Universiteit Antwerpen, Intel Exascience lab Flanders


## Reference
P. Ghysels and W. Vanroose, "Hiding global synchronization latency in the preconditioned Conjugate Gradient algorithm",
Submitted to Parallel Computing, 2012.


## See Also
 [](chapter_ksp), [](sec_pipelineksp), [](doc_faq_pipelined), `KSPCreate()`, `KSPSetType()`, `KSPPIPECG`, `KSPGROPPCG`, `KSPPGMRES`, `KSPCG`, `KSPCGUseSingleReduction()`

## Level
intermediate

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/impls/cr/pipecr/pipecr.c.html#KSPPIPECR">src/ksp/ksp/impls/cr/pipecr/pipecr.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/ksp/ksp/impls/cr/pipecr/pipecr.c)


[Index of all KSP routines](index.md)  
[Table of Contents for all manual pages](/docs/manualpages/index.md)  
[Index of all manual pages](/docs/manualpages/singleindex.md)  
