dlaic1(3) [centos man page]

dlaic1.f(3)							      LAPACK							       dlaic1.f(3)

NAME

       dlaic1.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dlaic1 (JOB, J, X, SEST, W, GAMMA, SESTPR, S, C)
	   DLAIC1 applies one step of incremental condition estimation.

Function/Subroutine Documentation
   subroutine dlaic1 (integerJOB, integerJ, double precision, dimension( j )X, double precisionSEST, double precision, dimension( j )W, double
       precisionGAMMA, double precisionSESTPR, double precisionS, double precisionC)
       DLAIC1 applies one step of incremental condition estimation.

       Purpose:

	    DLAIC1 applies one step of incremental condition estimation in
	    its simplest version:

	    Let x, twonorm(x) = 1, be an approximate singular vector of an j-by-j
	    lower triangular matrix L, such that
		     twonorm(L*x) = sest
	    Then DLAIC1 computes sestpr, s, c such that
	    the vector
			    [ s*x ]
		     xhat = [  c  ]
	    is an approximate singular vector of
			    [ L       0  ]
		     Lhat = [ w**T gamma ]
	    in the sense that
		     twonorm(Lhat*xhat) = sestpr.

	    Depending on JOB, an estimate for the largest or smallest singular
	    value is computed.

	    Note that [s c]**T and sestpr**2 is an eigenpair of the system

		diag(sest*sest, 0) + [alpha  gamma] * [ alpha ]
						      [ gamma ]

	    where  alpha =  x**T*w.

       Parameters:
	   JOB

		     JOB is INTEGER
		     = 1: an estimate for the largest singular value is computed.
		     = 2: an estimate for the smallest singular value is computed.

	   J

		     J is INTEGER
		     Length of X and W

	   X

		     X is DOUBLE PRECISION array, dimension (J)
		     The j-vector x.

	   SEST

		     SEST is DOUBLE PRECISION
		     Estimated singular value of j by j matrix L

	   W

		     W is DOUBLE PRECISION array, dimension (J)
		     The j-vector w.

	   GAMMA

		     GAMMA is DOUBLE PRECISION
		     The diagonal element gamma.

	   SESTPR

		     SESTPR is DOUBLE PRECISION
		     Estimated singular value of (j+1) by (j+1) matrix Lhat.

	   S

		     S is DOUBLE PRECISION
		     Sine needed in forming xhat.

	   C

		     C is DOUBLE PRECISION
		     Cosine needed in forming xhat.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Definition at line 135 of file dlaic1.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       dlaic1.f(3)