Visible to Intel only — GUID: GUID-51982739-97CC-4E6C-89CD-D0C161243816
Visible to Intel only — GUID: GUID-51982739-97CC-4E6C-89CD-D0C161243816
?lacon
Estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.
Syntax
call slacon( n, v, x, isgn, est, kase )
call dlacon( n, v, x, isgn, est, kase )
call clacon( n, v, x, est, kase )
call zlacon( n, v, x, est, kase )
Include Files
- mkl.fi
Description
The routine estimates the 1-norm of a square, real/complex matrix A. Reverse communication is used for evaluating matrix-vector products.
The ?lacon routine is not thread-safe. It is deprecated and retained for the backward compatibility only. Use the thread-safe ?lacn2 routine instead.
Input Parameters
- n
-
INTEGER. The order of the matrix A (n≥ 1).
- v, x
-
REAL for slacon
DOUBLE PRECISION for dlacon
COMPLEX for clacon
DOUBLE COMPLEX for zlacon.
Arrays, DIMENSION (n) each.
v is a workspace array.
x is used as input after an intermediate return.
- isgn
-
INTEGER.
Workspace array, DIMENSION (n), used with real flavors only.
- est
-
REAL for slacon/clacon
DOUBLE PRECISION for dlacon/zlacon
An estimate that with kase=1 or 2 should be unchanged from the previous call to ?lacon.
- kase
-
INTEGER.
On the initial call to ?lacon, kase should be 0.
Output Parameters
- est
-
REAL for slacon/clacon
DOUBLE PRECISION for dlacon/zlacon
An estimate (a lower bound) for norm(A).
- kase
-
On an intermediate return, kase will be 1 or 2, indicating whether x should be overwritten by A*x or AT*x for real flavors and A*x or AH*x for complex flavors. On the final return from ?lacon, kase will again be 0.
- v
-
On the final return, v = A*w, where est = norm(v)/norm(w) (w is not returned).
- x
-
On an intermediate return, x should be overwritten by
A*x, if kase = 1,
AT*x, if kase = 2 (for real flavors),
AH*x, if kase = 2 (for complex flavors),
and ?lacon must be re-called with all the other parameters unchanged.