Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?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
slacon dlacon clacon zlacon
The routine estimates the 1-norm of a square, real/complex matrix A . Reverse communication is used for evaluating matrix-vector products.
warning
The ?lacon routine is not thread-safe. It is deprecated and retained for the backward compatibility only. Use the thread-safe ?lacn2 (Estimates the 1-norm of a square matrix, using reverse communication for evaluating matrix-vector products.) 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 A:code:`T` * x for real flavors and A * x or A:code:`H` * 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 , A^{T}*x , if kase = 2 (for real flavors), A^{H}*x , if kase = 2 (for complex flavors), and ?lacon must be re-called with all the other parameters unchanged.