NAME

       dlasq3.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dlasq3 (I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE,
           TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU)
           DLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

Function/Subroutine Documentation

   subroutine dlasq3 (integerI0, integerN0, double precision, dimension( * )Z, integerPP, double
       precisionDMIN, double precisionSIGMA, double precisionDESIG, double precisionQMAX,
       integerNFAIL, integerITER, integerNDIV, logicalIEEE, integerTTYPE, double precisionDMIN1,
       double precisionDMIN2, double precisionDN, double precisionDN1, double precisionDN2,
       double precisionG, double precisionTAU)
       DLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

       Purpose:

            DLASQ3 checks for deflation, computes a shift (TAU) and calls dqds.
            In case of failure it changes shifts, and tries again until output
            is positive.

       Parameters:
           I0

                     I0 is INTEGER
                    First index.

           N0

                     N0 is INTEGER
                    Last index.

           Z

                     Z is DOUBLE PRECISION array, dimension ( 4*N )
                    Z holds the qd array.

           PP

                     PP is INTEGER
                    PP=0 for ping, PP=1 for pong.
                    PP=2 indicates that flipping was applied to the Z array
                    and that the initial tests for deflation should not be
                    performed.

           DMIN

                     DMIN is DOUBLE PRECISION
                    Minimum value of d.

           SIGMA

                     SIGMA is DOUBLE PRECISION
                    Sum of shifts used in current segment.

           DESIG

                     DESIG is DOUBLE PRECISION
                    Lower order part of SIGMA

           QMAX

                     QMAX is DOUBLE PRECISION
                    Maximum value of q.

           NFAIL

                     NFAIL is INTEGER
                    Number of times shift was too big.

           ITER

                     ITER is INTEGER
                    Number of iterations.

           NDIV

                     NDIV is INTEGER
                    Number of divisions.

           IEEE

                     IEEE is LOGICAL
                    Flag for IEEE or non IEEE arithmetic (passed to DLASQ5).

           TTYPE

                     TTYPE is INTEGER
                    Shift type.

           DMIN1

                     DMIN1 is DOUBLE PRECISION

           DMIN2

                     DMIN2 is DOUBLE PRECISION

           DN

                     DN is DOUBLE PRECISION

           DN1

                     DN1 is DOUBLE PRECISION

           DN2

                     DN2 is DOUBLE PRECISION

           G

                     G is DOUBLE PRECISION

           TAU

                     TAU is DOUBLE PRECISION

                    These are passed as arguments in order to save their values
                    between calls to DLASQ3.

       Author:
           Univ. of Tennessee

           Univ. of California Berkeley

           Univ. of Colorado Denver

           NAG Ltd.

       Date:
           September 2012

       Definition at line 181 of file dlasq3.f.

Author

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