128 SUBROUTINE dgecon( NORM, N, A, LDA, ANORM, RCOND, WORK, IWORK,
138 DOUBLE PRECISION ANORM, RCOND
142 DOUBLE PRECISION A( LDA, * ), WORK( * )
148 DOUBLE PRECISION ONE, ZERO
149 parameter( one = 1.0d+0, zero = 0.0d+0 )
154 INTEGER IX, KASE, KASE1
155 DOUBLE PRECISION AINVNM, SCALE, SL, SMLNUM, SU, HUGEVAL
161 LOGICAL LSAME, DISNAN
163 DOUBLE PRECISION DLAMCH
164 EXTERNAL lsame, idamax, dlamch, disnan
174 hugeval = dlamch(
'Overflow' )
179 onenrm = norm.EQ.
'1' .OR. lsame( norm,
'O' )
180 IF( .NOT.onenrm .AND. .NOT.lsame( norm,
'I' ) )
THEN
182 ELSE IF( n.LT.0 )
THEN
184 ELSE IF( lda.LT.max( 1, n ) )
THEN
186 ELSE IF( anorm.LT.zero )
THEN
190 CALL xerbla(
'DGECON', -info )
200 ELSE IF( anorm.EQ.zero )
THEN
202 ELSE IF( disnan( anorm ) )
THEN
206 ELSE IF( anorm.GT.hugeval )
THEN
211 smlnum = dlamch(
'Safe minimum' )
224 CALL dlacn2( n, work( n+1 ), work, iwork, ainvnm, kase, isave )
226 IF( kase.EQ.kase1 )
THEN
230 CALL dlatrs(
'Lower',
'No transpose',
'Unit', normin, n,
232 $ lda, work, sl, work( 2*n+1 ), info )
236 CALL dlatrs(
'Upper',
'No transpose',
'Non-unit', normin,
238 $ a, lda, work, su, work( 3*n+1 ), info )
243 CALL dlatrs(
'Upper',
'Transpose',
'Non-unit', normin, n,
245 $ lda, work, su, work( 3*n+1 ), info )
249 CALL dlatrs(
'Lower',
'Transpose',
'Unit', normin, n, a,
250 $ lda, work, sl, work( 2*n+1 ), info )
257 IF( scale.NE.one )
THEN
258 ix = idamax( n, work, 1 )
259 IF( scale.LT.abs( work( ix ) )*smlnum .OR. scale.EQ.zero )
261 CALL drscl( n, scale, work, 1 )
268 IF( ainvnm.NE.zero )
THEN
269 rcond = ( one / ainvnm ) / anorm
277 IF( disnan( rcond ) .OR. rcond.GT.hugeval )
subroutine dgecon(norm, n, a, lda, anorm, rcond, work, iwork, info)
DGECON
subroutine dlacn2(n, v, x, isgn, est, kase, isave)
DLACN2 estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vec...
subroutine dlatrs(uplo, trans, diag, normin, n, a, lda, x, scale, cnorm, info)
DLATRS solves a triangular system of equations with the scale factor set to prevent overflow.
subroutine drscl(n, sa, sx, incx)
DRSCL multiplies a vector by the reciprocal of a real scalar.