p?lantr

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

Version

Public

p?lantr

Returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element, of a triangular matrix.

Syntax

valpslantr ( norm , uplo , diag , m , n , a , ia , ja , desca , work )

valpdlantr ( norm , uplo , diag , m , n , a , ia , ja , desca , work )

valpclantr ( norm , uplo , diag , m , n , a , ia , ja , desca , work )

valpzlantr ( norm , uplo , diag , m , n , a , ia , ja , desca , work )

Include Files

mkl_scalapack.h

Description

pslantr pdlantr pclantr pzlantr The p?lantr routine function returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a trapezoidal or triangular distributed matrix sub(A) = A(ia:ia+m-1 , ja:ja+n-1) .

Input Parameters

norm

(global) CHARACTER . Specifies what value is returned by the routine :

= ‘M’ or ‘m’: val = max(abs(A_{ij})) , largest absolute value of the matrix A , it s not a matrix norm. = ‘1’ or ‘O’ or ‘o’: val = norm1(A) , 1-norm of the matrix A (maximum column sum), = ‘I’ or ‘i’: val = normI(A) , infinity norm of the matrix A (maximum row sum), = ‘F’ , ‘f’ , ‘E’ or ‘e’: val = normF(A) , Frobenius norm of the matrix A (square root of sum of squares).

uplo

(global) CHARACTER .

Specifies whether the upper or lower triangular part of the symmetric matrix sub( A ) is to be referenced. = ‘U’ : Upper trapezoidal, = ‘L’ : Lower trapezoidal. Note that sub( A ) is triangular instead of trapezoidal if m = n .

diag

(global) CHARACTER .

Specifies whether the distributed matrix sub( A ) has unit diagonal. = ‘N’ : Non-unit diagonal. = ‘U’ : Unit diagonal.

m

(global) INTEGER .

The number of rows in the distributed matrix sub( A ). When m = 0 , p?lantr is set to zero. m ≥ 0 .

n

(global) INTEGER .

The number of columns in the distributed matrix sub( A ). When n = 0 , p?lantr is set to zero. n ≥ 0 .

a

(local). REAL for pslantr DOUBLE PRECISION for pdlantr COMPLEX for pclantr COMPLEX*16 for pzlantr .

Pointer into the local memory to an array of size (lld_a, LOCc(ja+n-1)) containing the local pieces of the distributed matrix sub( A ).

ia , ja

(global) INTEGER .

The row and column indices in the global matrix A indicating the first row and the first column of the matrix sub( A ), respectively.

desca

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

work

(local). REAL for pslantr DOUBLE PRECISION for pdlantr COMPLEX for pclantr COMPLEX*16 for pzlantr . Array size lwork . lwork ≥ 0 if norm = ‘M’ or ‘m’ (not referenced), nq 0 if norm = ‘1’, ‘O’ or ‘o’ , mp 0 if norm = ‘I’ or ‘i’ , 0 if norm = 'F' , ‘f’ , ‘E’ or ‘e’ (not referenced), iroffa = mod(ia-1, mb_a ) , icoffa = mod( ja-1, nb_a) , iarow = indxg2p(ia, mb_a, myrow, rsrc_a, nprow),iacol = indxg2p(ja, nb_a, mycol, csrc_a, npcol) , mp0 = numroc(m+iroffa, mb_a, myrow, iarow, nprow) , nq0 = numroc(n+icoffa, nb_a, mycol, iacol, npcol) ,

indxg2p and numroc are ScaLAPACK tool functions; myrow , mycol , nprow , and npcol can be determined by calling the subroutine blacs_gridinfo .

Output Parameters

val

The value returned by the routine .

NOTE:

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

p?lantr

Syntax

Include Files

Description

Input Parameters

Output Parameters