LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
subroutine  zlaqr5 (WANTT, WANTZ, KACC22, N, KTOP, KBOT, NSHFTS, S, H, LDH, ILOZ, IHIZ, Z, LDZ, V, LDV, U, LDU, NV, WV, LDWV, NH, WH, LDWH) 
ZLAQR5 performs a single smallbulge multishift QR sweep. 
subroutine zlaqr5  (  logical  WANTT, 
logical  WANTZ,  
integer  KACC22,  
integer  N,  
integer  KTOP,  
integer  KBOT,  
integer  NSHFTS,  
complex*16, dimension( * )  S,  
complex*16, dimension( ldh, * )  H,  
integer  LDH,  
integer  ILOZ,  
integer  IHIZ,  
complex*16, dimension( ldz, * )  Z,  
integer  LDZ,  
complex*16, dimension( ldv, * )  V,  
integer  LDV,  
complex*16, dimension( ldu, * )  U,  
integer  LDU,  
integer  NV,  
complex*16, dimension( ldwv, * )  WV,  
integer  LDWV,  
integer  NH,  
complex*16, dimension( ldwh, * )  WH,  
integer  LDWH  
) 
ZLAQR5 performs a single smallbulge multishift QR sweep.
Download ZLAQR5 + dependencies [TGZ] [ZIP] [TXT]ZLAQR5, called by ZLAQR0, performs a single smallbulge multishift QR sweep.
[in]  WANTT  WANTT is logical scalar WANTT = .true. if the triangular Schur factor is being computed. WANTT is set to .false. otherwise. 
[in]  WANTZ  WANTZ is logical scalar WANTZ = .true. if the unitary Schur factor is being computed. WANTZ is set to .false. otherwise. 
[in]  KACC22  KACC22 is integer with value 0, 1, or 2. Specifies the computation mode of farfromdiagonal orthogonal updates. = 0: ZLAQR5 does not accumulate reflections and does not use matrixmatrix multiply to update farfromdiagonal matrix entries. = 1: ZLAQR5 accumulates reflections and uses matrixmatrix multiply to update the farfromdiagonal matrix entries. = 2: ZLAQR5 accumulates reflections, uses matrixmatrix multiply to update the farfromdiagonal matrix entries, and takes advantage of 2by2 block structure during matrix multiplies. 
[in]  N  N is integer scalar N is the order of the Hessenberg matrix H upon which this subroutine operates. 
[in]  KTOP  KTOP is integer scalar 
[in]  KBOT  KBOT is integer scalar These are the first and last rows and columns of an isolated diagonal block upon which the QR sweep is to be applied. It is assumed without a check that either KTOP = 1 or H(KTOP,KTOP1) = 0 and either KBOT = N or H(KBOT+1,KBOT) = 0. 
[in]  NSHFTS  NSHFTS is integer scalar NSHFTS gives the number of simultaneous shifts. NSHFTS must be positive and even. 
[in,out]  S  S is COMPLEX*16 array of size (NSHFTS) S contains the shifts of origin that define the multi shift QR sweep. On output S may be reordered. 
[in,out]  H  H is COMPLEX*16 array of size (LDH,N) On input H contains a Hessenberg matrix. On output a multishift QR sweep with shifts SR(J)+i*SI(J) is applied to the isolated diagonal block in rows and columns KTOP through KBOT. 
[in]  LDH  LDH is integer scalar LDH is the leading dimension of H just as declared in the calling procedure. LDH.GE.MAX(1,N). 
[in]  ILOZ  ILOZ is INTEGER 
[in]  IHIZ  IHIZ is INTEGER Specify the rows of Z to which transformations must be applied if WANTZ is .TRUE.. 1 .LE. ILOZ .LE. IHIZ .LE. N 
[in,out]  Z  Z is COMPLEX*16 array of size (LDZ,IHI) If WANTZ = .TRUE., then the QR Sweep unitary similarity transformation is accumulated into Z(ILOZ:IHIZ,ILO:IHI) from the right. If WANTZ = .FALSE., then Z is unreferenced. 
[in]  LDZ  LDZ is integer scalar LDA is the leading dimension of Z just as declared in the calling procedure. LDZ.GE.N. 
[out]  V  V is COMPLEX*16 array of size (LDV,NSHFTS/2) 
[in]  LDV  LDV is integer scalar LDV is the leading dimension of V as declared in the calling procedure. LDV.GE.3. 
[out]  U  U is COMPLEX*16 array of size (LDU,3*NSHFTS3) 
[in]  LDU  LDU is integer scalar LDU is the leading dimension of U just as declared in the in the calling subroutine. LDU.GE.3*NSHFTS3. 
[in]  NH  NH is integer scalar NH is the number of columns in array WH available for workspace. NH.GE.1. 
[out]  WH  WH is COMPLEX*16 array of size (LDWH,NH) 
[in]  LDWH  LDWH is integer scalar Leading dimension of WH just as declared in the calling procedure. LDWH.GE.3*NSHFTS3. 
[in]  NV  NV is integer scalar NV is the number of rows in WV agailable for workspace. NV.GE.1. 
[out]  WV  WV is COMPLEX*16 array of size (LDWV,3*NSHFTS3) 
[in]  LDWV  LDWV is integer scalar LDWV is the leading dimension of WV as declared in the in the calling subroutine. LDWV.GE.NV. 
Definition at line 250 of file zlaqr5.f.