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SymSchurLargestEigenVal

Largest eigen value of Schur’s matrix.

Interface​

INTERFACE
  MODULE FUNCTION SymSchurLargestEigenVal(obj, B, nev, which, NCV, &
      & maxIter, tol) RESULT(ans)
    CLASS(BlockMatrixField_), INTENT(INOUT) :: obj
    !! CSRMatrix, symmetric
    CLASS(BlockMatrixField_), INTENT(INOUT) :: B
    !! B matrix, possibly rectangle
    INTEGER(I4B), INTENT(IN) :: nev
    !! number of eigenvalues requested
    CHARACTER(*), OPTIONAL, INTENT(IN) :: which
    !! `which = "LM"` ⇨ absolute largest eigenvalue
    !! `which = "LA"` ⇨ algebraic largest eigenvalue
    !! default is "LA"
    INTEGER(I4B), OPTIONAL, INTENT(IN) :: NCV
    !! Number of Lanczos vectors generated
    !! It must be greater than 1 and smaller than `size(mat,1)`
    !! Default is `NCV = MIN(n, MAX(2*nev+1, 20))`
    INTEGER(I4B), OPTIONAL, INTENT(IN) :: maxIter
    !! Maximum number of iteration default = `N*10`
    REAL(DFP), OPTIONAL, INTENT(IN) :: tol
    !! tolerance, default = 0.0
    REAL(DFP) :: ans(nev)
    !! first k, largest eigenvalue
  END FUNCTION SymSchurLargestEigenVal
END INTERFACE