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

 real function sla_gerpvgrw ( integer N, integer NCOLS, real, dimension( lda, * ) A, integer LDA, real, dimension( ldaf, * ) AF, integer LDAF )

SLA_GERPVGRW

Purpose:
``` SLA_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 REAL 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 REAL array, dimension (LDAF,N) The factors L and U from the factorization A = P*L*U as computed by SGETRF.``` [in] LDAF ``` LDAF is INTEGER The leading dimension of the array AF. LDAF >= max(1,N).```

Definition at line 96 of file sla_gerpvgrw.f.

97*
98* -- LAPACK computational routine --
99* -- LAPACK is a software package provided by Univ. of Tennessee, --
100* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
101*
102* .. Scalar Arguments ..
103 INTEGER N, NCOLS, LDA, LDAF
104* ..
105* .. Array Arguments ..
106 REAL A( LDA, * ), AF( LDAF, * )
107* ..
108*
109* =====================================================================
110*
111* .. Local Scalars ..
112 INTEGER I, J
113 REAL AMAX, UMAX, RPVGRW
114* ..
115* .. Intrinsic Functions ..
116 INTRINSIC abs, max, min
117* ..
118* .. Executable Statements ..
119*
120 rpvgrw = 1.0
121
122 DO j = 1, ncols
123 amax = 0.0
124 umax = 0.0
125 DO i = 1, n
126 amax = max( abs( a( i, j ) ), amax )
127 END DO
128 DO i = 1, j
129 umax = max( abs( af( i, j ) ), umax )
130 END DO
131 IF ( umax /= 0.0 ) THEN
132 rpvgrw = min( amax / umax, rpvgrw )
133 END IF
134 END DO
135 sla_gerpvgrw = rpvgrw
136*
137* End of SLA_GERPVGRW
138*
real function sla_gerpvgrw(N, NCOLS, A, LDA, AF, LDAF)
SLA_GERPVGRW
Definition: sla_gerpvgrw.f:97
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