p?lacon

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

Version

Public

p?lacon

Estimates the 1-norm of a square matrix, using the reverse communication for evaluating matrix-vector products.

Syntax

call pslacon ( n , v , iv , jv , descv , x , ix , jx , descx , isgn , est , kase )

call pdlacon ( n , v , iv , jv , descv , x , ix , jx , descx , isgn , est , kase )

call pclacon ( n , v , iv , jv , descv , x , ix , jx , descx , isgn , est , kase )

call pzlacon ( n , v , iv , jv , descv , x , ix , jx , descx , isgn , est , kase )

Include Files

mkl_scalapack.h

Description

pslacon pdlacon pclacon pzlacon The p?lacon routine function estimates the 1-norm of a square, real/unitary distributed matrix A . Reverse communication is used for evaluating matrix-vector products. x and v are aligned with the distributed matrix A , this information is implicitly contained within iv , ix , descv , and descx .

Input Parameters

n

(global) INTEGER . The length of the distributed vectors v and x. n ≥ 0.

v: (local). REAL for pslacon DOUBLE PRECISION for pdlacon COMPLEX for pclacon COMPLEX*16 for pzlacon. Pointer into the local memory to an array of size LOCr ( n +mod( iv -1, mb_v )). On the final return, v = a*w , where est = norm( v )/norm( w ) ( w is not returned).

iv , jv

(global) INTEGER . The row and column indices in the global matrix V indicating the first row and the first column of the submatrix V , respectively.

descv

(global and local) INTEGER array of size dlen_ . The array descriptor for the distributed matrix V.

x: (local). REAL for pslacon DOUBLE PRECISION for pdlacon COMPLEX for pclacon COMPLEX*16 for pzlacon. Pointer into the local memory to an array of size LOCr ( n +mod( ix -1, mb_x )).

ix , jx

(global) INTEGER . The row and column indices in the global matrix X indicating the first row and the first column of the submatrix X , respectively.

descx

(global and local) INTEGER array of size dlen_ . The array descriptor for the distributed matrix X.

isgn

(local). INTEGER .

Array of size LOCr ( n +mod( ix -1, mb_x )). isgn is aligned with x and v .

kase

(local). INTEGER .

On the initial call to p?lacon , kase should be 0.

Output Parameters

x: (local). On an intermediate return, X should be overwritten by A * X , if kase =1, A' * X , if kase =2, p?lacon must be re-called with all the other parameters unchanged.

est

(global). REAL for single precision flavors

DOUBLE PRECISION for double precision flavors

kase

(local)

INTEGER . On an intermediate return, kase is 1 or 2, indicating whether X should be overwritten by A*X, or A'*X . On the final return from p?lacon , kase is again 0.

NOTE:

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

p?lacon

Syntax

Include Files

Description

Input Parameters

Output Parameters