 LAPACK 3.11.0 LAPACK: Linear Algebra PACKage
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## ◆ dla_gerpvgrw()

 double precision function dla_gerpvgrw ( integer N, integer NCOLS, double precision, dimension( lda, * ) A, integer LDA, double precision, dimension( ldaf, * ) AF, integer LDAF )

DLA_GERPVGRW

Purpose:
``` DLA_GERPVGRW computes the reciprocal pivot growth factor
norm(A)/norm(U). The "max absolute element" norm is used. If this is
much less than 1, the stability of the LU factorization of the
(equilibrated) matrix A could be poor. This also means that the
solution X, estimated condition numbers, and error bounds could be
unreliable.```
Parameters
 [in] N ``` N is INTEGER The number of linear equations, i.e., the order of the matrix A. N >= 0.``` [in] NCOLS ``` NCOLS is INTEGER The number of columns of the matrix A. NCOLS >= 0.``` [in] A ``` A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the N-by-N matrix A.``` [in] LDA ``` LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).``` [in] AF ``` AF is DOUBLE PRECISION array, dimension (LDAF,N) The factors L and U from the factorization A = P*L*U as computed by DGETRF.``` [in] LDAF ``` LDAF is INTEGER The leading dimension of the array AF. LDAF >= max(1,N).```

Definition at line 98 of file dla_gerpvgrw.f.

100*
101* -- LAPACK computational routine --
102* -- LAPACK is a software package provided by Univ. of Tennessee, --
103* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
104*
105* .. Scalar Arguments ..
106 INTEGER N, NCOLS, LDA, LDAF
107* ..
108* .. Array Arguments ..
109 DOUBLE PRECISION A( LDA, * ), AF( LDAF, * )
110* ..
111*
112* =====================================================================
113*
114* .. Local Scalars ..
115 INTEGER I, J
116 DOUBLE PRECISION AMAX, UMAX, RPVGRW
117* ..
118* .. Intrinsic Functions ..
119 INTRINSIC abs, max, min
120* ..
121* .. Executable Statements ..
122*
123 rpvgrw = 1.0d+0
124
125 DO j = 1, ncols
126 amax = 0.0d+0
127 umax = 0.0d+0
128 DO i = 1, n
129 amax = max( abs( a( i, j ) ), amax )
130 END DO
131 DO i = 1, j
132 umax = max( abs( af( i, j ) ), umax )
133 END DO
134 IF ( umax /= 0.0d+0 ) THEN
135 rpvgrw = min( amax / umax, rpvgrw )
136 END IF
137 END DO
138 dla_gerpvgrw = rpvgrw
139*
140* End of DLA_GERPVGRW
141*
double precision function dla_gerpvgrw(N, NCOLS, A, LDA, AF, LDAF)
DLA_GERPVGRW
Definition: dla_gerpvgrw.f:100
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