lasq3 - lasq3: dqds step

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subroutinedlasq3(integeri0,integern0,doubleprecision,dimension(*)z,integerpp,doubleprecisiondmin,doubleprecisionsigma,doubleprecisiondesig,doubleprecisionqmax,integernfail,integeriter,integerndiv,logicalieee,integerttype,doubleprecisiondmin1,doubleprecisiondmin2,doubleprecisiondn,doubleprecisiondn1,doubleprecisiondn2,doubleprecisiong,doubleprecisiontau)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. ParametersI0 I0 is INTEGER First index. N0 N0 is INTEGER Last index. Z Z is DOUBLE PRECISION array, dimension ( 4*N0 ) 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 Increment NFAIL by 1 each time the shift was too big. ITER ITER is INTEGER Increment ITER by 1 for each iteration. NDIV NDIV is INTEGER Increment NDIV by 1 for each division. 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. subroutineslasq3(integeri0,integern0,real,dimension(*)z,integerpp,realdmin,realsigma,realdesig,realqmax,integernfail,integeriter,integerndiv,logicalieee,integerttype,realdmin1,realdmin2,realdn,realdn1,realdn2,realg,realtau)SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr. Purpose: SLASQ3 checks for deflation, computes a shift (TAU) and calls dqds. In case of failure it changes shifts, and tries again until output is positive. ParametersI0 I0 is INTEGER First index. N0 N0 is INTEGER Last index. Z Z is REAL array, dimension ( 4*N0 ) 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 REAL Minimum value of d. SIGMA SIGMA is REAL Sum of shifts used in current segment. DESIG DESIG is REAL Lower order part of SIGMA QMAX QMAX is REAL Maximum value of q. NFAIL NFAIL is INTEGER Increment NFAIL by 1 each time the shift was too big. ITER ITER is INTEGER Increment ITER by 1 for each iteration. NDIV NDIV is INTEGER Increment NDIV by 1 for each division. IEEE IEEE is LOGICAL Flag for IEEE or non IEEE arithmetic (passed to SLASQ5). TTYPE TTYPE is INTEGER Shift type. DMIN1 DMIN1 is REAL DMIN2 DMIN2 is REAL DN DN is REAL DN1 DN1 is REAL DN2 DN2 is REAL G G is REAL TAU TAU is REAL These are passed as arguments in order to save their values between calls to SLASQ3. Author Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd.

lasq3 - lasq3: dqds step

Functions 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. subroutine slasq3 (i0, n0, z, pp, dmin, sigma, desig, qmax, nfail, iter, ndiv, ieee, ttype, dmin1, dmin2, dn, dn1, dn2, g, tau) SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.