NAME

SRC/slaqz4.f

SYNOPSIS

Functions/Subroutines

subroutine slaqz4 (ilschur, ilq, ilz, n, ilo, ihi, nshifts, nblock_desired, sr, si, ss, a, lda, b, ldb, q, ldq, z, ldz, qc, ldqc, zc, ldzc, work, lwork, info)
SLAQZ4

Function/Subroutine Documentation

subroutine slaqz4 (logical, intent(in) ilschur, logical, intent(in) ilq, logical, intent(in) ilz, integer, intent(in) n, integer, intent(in) ilo, integer, intent(in) ihi, integer, intent(in) nshifts, integer, intent(in) nblock_desired, real, dimension( * ), intent(inout) sr, real, dimension( * ), intent(inout) si, real, dimension( * ), intent(inout) ss, real, dimension( lda, * ), intent(inout) a, integer, intent(in) lda, real, dimension( ldb, * ), intent(inout) b, integer, intent(in) ldb, real, dimension( ldq, * ), intent(inout) q, integer, intent(in) ldq, real, dimension( ldz, * ), intent(inout) z, integer, intent(in) ldz, real, dimension( ldqc, * ), intent(inout) qc, integer, intent(in) ldqc, real, dimension( ldzc, * ), intent(inout) zc, integer, intent(in) ldzc, real, dimension( * ), intent(inout) work, integer, intent(in) lwork, integer, intent(out) info)

SLAQZ4

Purpose:



 SLAQZ4 Executes a single multishift QZ sweep

Parameters

ILSCHUR



          ILSCHUR is LOGICAL


              Determines whether or not to update the full Schur form

ILQ



          ILQ is LOGICAL


              Determines whether or not to update the matrix Q

ILZ



          ILZ is LOGICAL


              Determines whether or not to update the matrix Z



          N is INTEGER


          The order of the matrices A, B, Q, and Z.  N >= 0.

ILO



          ILO is INTEGER

IHI



          IHI is INTEGER

NSHIFTS



          NSHIFTS is INTEGER


          The desired number of shifts to use

NBLOCK_DESIRED



          NBLOCK_DESIRED is INTEGER


          The desired size of the computational windows



          SR is REAL array. SR contains


          the real parts of the shifts to use.



          SI is REAL array. SI contains


          the imaginary parts of the shifts to use.



          SS is REAL array. SS contains


          the scale of the shifts to use.



          A is REAL array, dimension (LDA, N)

LDA



          LDA is INTEGER


          The leading dimension of the array A.  LDA >= max( 1, N ).



          B is REAL array, dimension (LDB, N)

LDB



          LDB is INTEGER


          The leading dimension of the array B.  LDB >= max( 1, N ).



          Q is REAL array, dimension (LDQ, N)

LDQ



          LDQ is INTEGER



          Z is REAL array, dimension (LDZ, N)

LDZ



          LDZ is INTEGER



          QC is REAL array, dimension (LDQC, NBLOCK_DESIRED)

LDQC



          LDQC is INTEGER



          ZC is REAL array, dimension (LDZC, NBLOCK_DESIRED)

LDZC



          LDZ is INTEGER

WORK



          WORK is REAL array, dimension (MAX(1,LWORK))


          On exit, if INFO >= 0, WORK(1) returns the optimal LWORK.

LWORK



          LWORK is INTEGER


          The dimension of the array WORK.  LWORK >= max(1,N).


          If LWORK = -1, then a workspace query is assumed; the routine


          only calculates the optimal size of the WORK array, returns


          this value as the first entry of the WORK array, and no error


          message related to LWORK is issued by XERBLA.

INFO



          INFO is INTEGER


          = 0: successful exit


          < 0: if INFO = -i, the i-th argument had an illegal value

Author

Thijs Steel, KU Leuven

Date

May 2020

Definition at line 210 of file slaqz4.f.

Author

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