LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

Go to the source code of this file.
Functions/Subroutines  
subroutine  dlaqtr (LTRAN, LREAL, N, T, LDT, B, W, SCALE, X, WORK, INFO) 
DLAQTR solves a real quasitriangular system of equations, or a complex quasitriangular system of special form, in real arithmetic. 
subroutine dlaqtr  (  logical  LTRAN, 
logical  LREAL,  
integer  N,  
double precision, dimension( ldt, * )  T,  
integer  LDT,  
double precision, dimension( * )  B,  
double precision  W,  
double precision  SCALE,  
double precision, dimension( * )  X,  
double precision, dimension( * )  WORK,  
integer  INFO  
) 
DLAQTR solves a real quasitriangular system of equations, or a complex quasitriangular system of special form, in real arithmetic.
Download DLAQTR + dependencies [TGZ] [ZIP] [TXT]DLAQTR solves the real quasitriangular system op(T)*p = scale*c, if LREAL = .TRUE. or the complex quasitriangular systems op(T + iB)*(p+iq) = scale*(c+id), if LREAL = .FALSE. in real arithmetic, where T is upper quasitriangular. If LREAL = .FALSE., then the first diagonal block of T must be 1 by 1, B is the specially structured matrix B = [ b(1) b(2) ... b(n) ] [ w ] [ w ] [ . ] [ w ] op(A) = A or A**T, A**T denotes the transpose of matrix A. On input, X = [ c ]. On output, X = [ p ]. [ d ] [ q ] This subroutine is designed for the condition number estimation in routine DTRSNA.
[in]  LTRAN  LTRAN is LOGICAL On entry, LTRAN specifies the option of conjugate transpose: = .FALSE., op(T+i*B) = T+i*B, = .TRUE., op(T+i*B) = (T+i*B)**T. 
[in]  LREAL  LREAL is LOGICAL On entry, LREAL specifies the input matrix structure: = .FALSE., the input is complex = .TRUE., the input is real 
[in]  N  N is INTEGER On entry, N specifies the order of T+i*B. N >= 0. 
[in]  T  T is DOUBLE PRECISION array, dimension (LDT,N) On entry, T contains a matrix in Schur canonical form. If LREAL = .FALSE., then the first diagonal block of T mu be 1 by 1. 
[in]  LDT  LDT is INTEGER The leading dimension of the matrix T. LDT >= max(1,N). 
[in]  B  B is DOUBLE PRECISION array, dimension (N) On entry, B contains the elements to form the matrix B as described above. If LREAL = .TRUE., B is not referenced. 
[in]  W  W is DOUBLE PRECISION On entry, W is the diagonal element of the matrix B. If LREAL = .TRUE., W is not referenced. 
[out]  SCALE  SCALE is DOUBLE PRECISION On exit, SCALE is the scale factor. 
[in,out]  X  X is DOUBLE PRECISION array, dimension (2*N) On entry, X contains the right hand side of the system. On exit, X is overwritten by the solution. 
[out]  WORK  WORK is DOUBLE PRECISION array, dimension (N) 
[out]  INFO  INFO is INTEGER On exit, INFO is set to 0: successful exit. 1: the some diagonal 1 by 1 block has been perturbed by a small number SMIN to keep nonsingularity. 2: the some diagonal 2 by 2 block has been perturbed by a small number in DLALN2 to keep nonsingularity. NOTE: In the interests of speed, this routine does not check the inputs for errors. 
Definition at line 165 of file dlaqtr.f.