redhat man page for dgbequ

Query: dgbequ

OS: redhat

Section: l

Format: Original Unix Latex Style Formatted with HTML and a Horizontal Scroll Bar

DGBEQU(l)								 )								 DGBEQU(l)

NAME
DGBEQU - compute row and column scalings intended to equilibrate an M-by-N band matrix A and reduce its condition number
SYNOPSIS
SUBROUTINE DGBEQU( M, N, KL, KU, AB, LDAB, R, C, ROWCND, COLCND, AMAX, INFO ) INTEGER INFO, KL, KU, LDAB, M, N DOUBLE PRECISION AMAX, COLCND, ROWCND DOUBLE PRECISION AB( LDAB, * ), C( * ), R( * )
PURPOSE
DGBEQU computes row and column scalings intended to equilibrate an M-by-N band matrix A and reduce its condition number. R returns the row scale factors and C the column scale factors, chosen to try to make the largest element in each row and column of the matrix B with ele- ments B(i,j)=R(i)*A(i,j)*C(j) have absolute value 1. R(i) and C(j) are restricted to be between SMLNUM = smallest safe number and BIGNUM = largest safe number. Use of these scaling factors is not guaranteed to reduce the condition number of A but works well in practice.
ARGUMENTS
M (input) INTEGER The number of rows of the matrix A. M >= 0. N (input) INTEGER The number of columns of the matrix A. N >= 0. KL (input) INTEGER The number of subdiagonals within the band of A. KL >= 0. KU (input) INTEGER The number of superdiagonals within the band of A. KU >= 0. AB (input) DOUBLE PRECISION array, dimension (LDAB,N) The band matrix A, stored in rows 1 to KL+KU+1. The j-th column of A is stored in the j-th column of the array AB as follows: AB(ku+1+i-j,j) = A(i,j) for max(1,j-ku)<=i<=min(m,j+kl). LDAB (input) INTEGER The leading dimension of the array AB. LDAB >= KL+KU+1. R (output) DOUBLE PRECISION array, dimension (M) If INFO = 0, or INFO > M, R contains the row scale factors for A. C (output) DOUBLE PRECISION array, dimension (N) If INFO = 0, C contains the column scale factors for A. ROWCND (output) DOUBLE PRECISION If INFO = 0 or INFO > M, ROWCND contains the ratio of the smallest R(i) to the largest R(i). If ROWCND >= 0.1 and AMAX is neither too large nor too small, it is not worth scaling by R. COLCND (output) DOUBLE PRECISION If INFO = 0, COLCND contains the ratio of the smallest C(i) to the largest C(i). If COLCND >= 0.1, it is not worth scaling by C. AMAX (output) DOUBLE PRECISION Absolute value of largest matrix element. If AMAX is very close to overflow or very close to underflow, the matrix should be scaled. INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, and i is <= M: the i-th row of A is exactly zero > M: the (i-M)-th column of A is exactly zero LAPACK version 3.0 15 June 2000 DGBEQU(l)
Related Man Pages
dgeequ(l) - redhat
sgbequ(l) - redhat
zgeequ(l) - redhat
zgbequ.f(3) - debian
dgbequ(3) - centos
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