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slacon.f(3) | LAPACK | slacon.f(3) |
NAME¶
slacon.f -SYNOPSIS¶
Functions/Subroutines¶
subroutine slacon (N, V, X, ISGN, EST, KASE)
Function/Subroutine Documentation¶
subroutine slacon (integerN, real, dimension( * )V, real, dimension( * )X, integer, dimension( * )ISGN, realEST, integerKASE)¶
SLACON Purpose:SLACON estimates the 1-norm of a square, real matrix A. Reverse communication is used for evaluating matrix-vector products.
N
V
X
ISGN
EST
KASE
Author:
N is INTEGER The order of the matrix. N >= 1.
V is REAL array, dimension (N) On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
X is REAL array, dimension (N) On an intermediate return, X should be overwritten by A * X, if KASE=1, A**T * X, if KASE=2, and SLACON must be re-called with all the other parameters unchanged.
ISGN is INTEGER array, dimension (N)
EST is REAL On entry with KASE = 1 or 2 and JUMP = 3, EST should be unchanged from the previous call to SLACON. On exit, EST is an estimate (a lower bound) for norm(A).
KASE is INTEGER On the initial call to SLACON, KASE should be 0. On an intermediate return, KASE will be 1 or 2, indicating whether X should be overwritten by A * X or A**T * X. On the final return from SLACON, KASE will again be 0.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Contributors:
Nick Higham, University of Manchester.
Originally named SONEST, dated March 16, 1988.
References:
Originally named SONEST, dated March 16, 1988.
N.J. Higham, 'FORTRAN codes for estimating the
one-norm of
a real or complex matrix, with applications to condition estimation', ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.
a real or complex matrix, with applications to condition estimation', ACM Trans. Math. Soft., vol. 14, no. 4, pp. 381-396, December 1988.
Author¶
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