clacon (3) - Linux Manuals
subroutine clacon (integerN, complex, dimension( n )V, complex, dimension( n )X, realEST, integerKASE)
CLACON estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.
CLACON estimates the 1-norm of a square, complex matrix A. Reverse communication is used for evaluating matrix-vector products.
N is INTEGER The order of the matrix. N >= 1.
V is COMPLEX array, dimension (N) On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
X is COMPLEX array, dimension (N) On an intermediate return, X should be overwritten by A * X, if KASE=1, A**H * X, if KASE=2, where A**H is the conjugate transpose of A, and CLACON must be re-called with all the other parameters unchanged.
EST is REAL On entry with KASE = 1 or 2 and JUMP = 3, EST should be unchanged from the previous call to CLACON. On exit, EST is an estimate (a lower bound) for norm(A).
KASE is INTEGER On the initial call to CLACON, 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**H * X. On the final return from CLACON, KASE will again be 0.
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- September 2012
Originally named CONEST, dated March 16, 1988.
Last modified: April, 1999
- Nick Higham, University of Manchester
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.
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