Class Getvec


  • public class Getvec
    extends Object
    Computes the (scaled) r-th column of the inverse of the sub-matrix block of the tridiagonal matrix T = LDLT - λ I. This is essentially Algorithm Getvec.

    This is used to compute an Fernando and Parlett (FP) vector of a singleton in MRRR.

    See Also:
    • "Dhillon, Inderjit S. and Parlett, Beresford N., "Multiple representations to compute orthogonal eigenvectors of symmetric tridiagonal matrices", Linear Algebra and its Applications, 2004, 387, pp. 1-28."
    • "Dhillon, Inderjit S. and Parlett, Beresford N., "Orthogonal eigenvectors and relative gaps", SIAM Journal on Matrix Analysis and Applications, 2004, Vol. 25, pp. 858-899."
    • Constructor Detail

      • Getvec

        public Getvec​(LDDecomposition LDLt,
                      double lambda,
                      int twistIndex,
                      double gapTolerance,
                      double minPivot)
        Computes an FP vector of a singleton.
        Parameters:
        LDLt - the robust representation LDLT
        lambda - the shift λ
        twistIndex - the twist index r
        gapTolerance - the gap tolerance
        minPivot - the minimum pivot in the Sturm sequence for T
    • Method Detail

      • getNegCount

        public int getNegCount()
      • getTwistIndex

        public int getTwistIndex()
      • getInverseNorm

        public double getInverseNorm()
      • getResidual

        public double getResidual()
      • getRQCorrection

        public double getRQCorrection()
      • getFirstNonZeroIndex

        public int getFirstNonZeroIndex()
      • getLastNonZeroIndex

        public int getLastNonZeroIndex()
      • getEigenvector

        public Vector getEigenvector()