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template<typename T>
void lacn2(integer *n, T *v, T *x, integer *isgn, T *est, integer *kase, integer *isave)# LACN2 estimates the 1-norm of a square matrix.
Purpose:
LACN2 estimates the 1-norm of a square, real matrix A. Reverse communication is used for evaluating matrix-vector products.
- Parameters:
N – [in]
N is INTEGER
The order of the matrix. N >= 1.
V – [out]
V is REAL array, dimension (N)
On the final return, V = A*W, where EST = norm(V)/norm(W) (W is not returned).
X – [inout]
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 SLACN2 must be re-called with all the other parameters unchanged.ISGN – [out] ISGN is INTEGER array, dimension (N)
EST – [inout]
EST is REAL
On entry with KASE = 1 or 2 and ISAVE(1) = 3, EST should be unchanged from the previous call to SLACN2.
On exit, EST is an estimate (a lower bound) for norm(A).KASE – [inout]
KASE is INTEGER
On the initial call to SLACN2, 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 SLACN2, KASE will again be 0.ISAVE – [inout]
ISAVE is INTEGER array, dimension (3)
ISAVE is used to save variables between calls to SLACN2