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# EPSRQCG

EPSRQCG = “rqcg” - The Rayleigh Quotient Conjugate Gradient method.

## Notes

This is a preconditioned eigensolver for computing leftmost eigenvalues, similar to `EPSLOBPCG`, but usually less competitive.

The description of the method is in [Bergamaschi et al., 2006]

The preconditioner is specified via the internal `ST` object and its associated `KSP`.

## References

[Ber06]

L. Bergamaschi, A. Martínez, and G. Pini. Parallel preconditioned conjugate gradient optimization of the Rayleigh quotient for the solution of sparse eigenproblems. Appl. Math. Comput., 175(2):1694–1715, 2006. doi:10.1016/j.amc.2005.09.015.

## See Also

EPS: Eigenvalue Problem Solver, `EPS`, `EPSType`, `EPSSetType()`, `EPSGetST()`

## Level

beginner

## Location

src/eps/impls/cg/rqcg/rqcg.c

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