TESTING/LIN/sqrt17.f(3) | Library Functions Manual | TESTING/LIN/sqrt17.f(3) |
NAME
TESTING/LIN/sqrt17.f
SYNOPSIS
Functions/Subroutines
real function sqrt17 (trans, iresid, m, n, nrhs, a, lda, x,
ldx, b, ldb, c, work, lwork)
SQRT17
Function/Subroutine Documentation
real function sqrt17 (character trans, integer iresid, integer m, integer n, integer nrhs, real, dimension( lda, * ) a, integer lda, real, dimension( ldx, * ) x, integer ldx, real, dimension( ldb, * ) b, integer ldb, real, dimension( ldb, * ) c, real, dimension( lwork ) work, integer lwork)
SQRT17
Purpose:
SQRT17 computes the ratio norm(R**T * op(A)) / ( norm(A) * alpha * max(M,N,NRHS) * EPS ), where R = B - op(A)*X, op(A) is A or A**T, depending on TRANS, EPS is the machine epsilon, and alpha = norm(B) if IRESID = 1 (zero-residual problem) alpha = norm(R) if IRESID = 2 (otherwise). The norm used is the 1-norm.
Parameters
TRANS
TRANS is CHARACTER*1 Specifies whether or not the transpose of A is used. = 'N': No transpose, op(A) = A. = 'T': Transpose, op(A) = A**T.
IRESID
IRESID is INTEGER IRESID = 1 indicates zero-residual problem. IRESID = 2 indicates non-zero residual.
M
M is INTEGER The number of rows of the matrix A. If TRANS = 'N', the number of rows of the matrix B. If TRANS = 'T', the number of rows of the matrix X.
N
N is INTEGER The number of columns of the matrix A. If TRANS = 'N', the number of rows of the matrix X. If TRANS = 'T', the number of rows of the matrix B.
NRHS
NRHS is INTEGER The number of columns of the matrices X and B.
A
A is REAL array, dimension (LDA,N) The m-by-n matrix A.
LDA
LDA is INTEGER The leading dimension of the array A. LDA >= M.
X
X is REAL array, dimension (LDX,NRHS) If TRANS = 'N', the n-by-nrhs matrix X. If TRANS = 'T', the m-by-nrhs matrix X.
LDX
LDX is INTEGER The leading dimension of the array X. If TRANS = 'N', LDX >= N. If TRANS = 'T', LDX >= M.
B
B is REAL array, dimension (LDB,NRHS) If TRANS = 'N', the m-by-nrhs matrix B. If TRANS = 'T', the n-by-nrhs matrix B.
LDB
LDB is INTEGER The leading dimension of the array B. If TRANS = 'N', LDB >= M. If TRANS = 'T', LDB >= N.
C
C is REAL array, dimension (LDB,NRHS)
WORK
WORK is REAL array, dimension (LWORK)
LWORK
LWORK is INTEGER The length of the array WORK. LWORK >= NRHS*(M+N).
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Definition at line 151 of file sqrt17.f.
Author
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