97 REAL function
sqrt11( m, k, a, lda, tau, work, lwork )
104 INTEGER k, lda, lwork, m
107 REAL a( lda, * ), tau( * ), work( lwork )
114 parameter( zero = 0.0e0, one = 1.0e0 )
138 IF( lwork.LT.m*m+m )
THEN
139 CALL xerbla(
'SQRT11', 7 )
148 CALL slaset(
'Full', m, m, zero, one, work, m )
152 CALL sorm2r(
'Left',
'No transpose', m, m, k, a, lda, tau, work,
153 $ m, work( m*m+1 ), info )
157 CALL sorm2r(
'Left',
'Transpose', m, m, k, a, lda, tau, work, m,
158 $ work( m*m+1 ), info )
161 work( ( j-1 )*m+j ) = work( ( j-1 )*m+j ) - one
165 $ ( real( m )*
slamch(
'Epsilon' ) )
subroutine slaset(UPLO, M, N, ALPHA, BETA, A, LDA)
SLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values.
subroutine xerbla(SRNAME, INFO)
XERBLA
real function slange(NORM, M, N, A, LDA, WORK)
SLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
subroutine sorm2r(SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, INFO)
SORM2R multiplies a general matrix by the orthogonal matrix from a QR factorization determined by sge...
real function sqrt11(M, K, A, LDA, TAU, WORK, LWORK)
SQRT11
real function slamch(CMACH)
SLAMCH