GNU/Linux man pages
Livre :
Expressions régulières,
Syntaxe et mise en oeuvre :
GNU/Linux |
CentOS 4.8 |
i386 |
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dtrcon(l) |
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DTRCON - estimate the reciprocal of the condition number of a triangular matrix A, in either the 1-norm or the infinity-norm
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SUBROUTINE DTRCON( |
NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK, IWORK, INFO ) | ||
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CHARACTER |
DIAG, NORM, UPLO | ||
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INTEGER |
INFO, LDA, N | ||
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DOUBLE |
PRECISION RCOND | ||
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INTEGER |
IWORK( * ) | ||
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DOUBLE |
PRECISION A( LDA, * ), WORK( * ) |
DTRCON
estimates the reciprocal of the condition number of a
triangular matrix A, in either the 1-norm or the
infinity-norm. The norm of A is computed and an estimate is
obtained for norm(inv(A)), then the reciprocal of the
condition number is computed as
RCOND = 1 / ( norm(A) * norm(inv(A)) ).
NORM (input) CHARACTER*1
Specifies whether the 1-norm
condition number or the infinity-norm condition number is
required:
= ’1’ or ’O’: 1-norm;
= ’I’: Infinity-norm.
UPLO (input) CHARACTER*1
= ’U’: A is upper
triangular;
= ’L’: A is lower triangular.
DIAG (input) CHARACTER*1
= ’N’: A is
non-unit triangular;
= ’U’: A is unit triangular.
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input) DOUBLE PRECISION array, dimension (LDA,N)
The triangular matrix A. If UPLO = ’U’, the leading N-by-N upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = ’L’, the leading N-by-N lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = ’U’, the diagonal elements of A are also not referenced and are assumed to be 1.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
RCOND (output) DOUBLE PRECISION
The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
WORK (workspace) DOUBLE
PRECISION array, dimension (3*N)
IWORK (workspace) INTEGER array, dimension (N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal
value
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dtrcon(l) | |