[petsc-users] SVD residual estimates with SLEPc

[Jose E. Roman]

El 05/07/2012, a las 11:29, Miguel Fosas escribió:

> Hi everyone,
> 
> I am using SLEPc to compute singular values from a shell matrix A (whose matrix-vector product is very costly to evaluate). After the singular value's are computed, I would like to obtain the error. For this purpose, SLEPc provides the function SVDComputeResidualNorms. However, this function needs to apply twice the operator A, which makes the calculation almost as twice as long (for my case).
> 
> I know that the estimates that are printed by the monitors (-svd_monitor_all) are pretty good. Is there a way to retrieve the value of such estimates from the internal structures of SLEPc?
> 
> Thanks,
> 
> Miguel

This is available for EPS, with EPSGetErrorEstimate(), but not for SVD. If you use an EPS for the SVD solver (that is, SVDCROSS or SVDCYCLIC) then you should be able to extract the EPS object with SVDGetEPS() and use the above function.

Jose