---
name: "clantp"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/clantp/3lapack"
---

# clantp(3lapack)

returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a triangular matrix A, supplied in packed form

## NAME

CLANTP - returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a triangular matrix A, supplied in packed form

## SYNOPSIS

- REAL FUNCTION

  CLANTP( NORM, UPLO, DIAG, N, AP, WORK )

- CHARACTER

  DIAG, NORM, UPLO

- INTEGER

  N

- REAL

  WORK( \* )

- COMPLEX

  AP( \* )

## PURPOSE

CLANTP  returns the value of the one norm,  or the Frobenius norm, or the  infinity norm,  or the  element of  largest absolute value  of a triangular matrix A, supplied in packed form.

## DESCRIPTION

CLANTP returns the value\
\
    CLANTP = ( max(abs(A(i,j))), NORM = 'M' or 'm'\
\
             (\
\
             ( norm1(A),         NORM = '1', 'O' or 'o'\
\
             (\
\
             ( normI(A),         NORM = 'I' or 'i'\
\
             (\
\
             ( normF(A),         NORM = 'F', 'f', 'E' or 'e' where  norm1  denotes the  one norm of a matrix (maximum column sum), normI  denotes the  infinity norm  of a matrix  (maximum row sum) and normF  denotes the  Frobenius norm of a matrix (square root of sum of squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.

## ARGUMENTS

- NORM (input) CHARACTER\*1

  Specifies the value to be returned in CLANTP as described above.

- UPLO (input) CHARACTER\*1

  Specifies whether the matrix A is upper or lower triangular. = 'U':  Upper triangular\
   \= 'L':  Lower triangular

- DIAG (input) CHARACTER\*1

  Specifies whether or not the matrix A is unit triangular. = 'N':  Non-unit triangular\
   \= 'U':  Unit triangular

- N (input) INTEGER

  The order of the matrix A.  N \>= 0.  When N = 0, CLANTP is set to zero.

- AP (input) COMPLEX array, dimension (N\*(N+1)/2)

  The upper or lower triangular matrix A, packed columnwise in a linear array.  The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)\*j/2) = A(i,j) for 1\<=i\<=j; if UPLO = 'L', AP(i + (j-1)\*(2n-j)/2) = A(i,j) for j\<=i\<=n. Note that when DIAG = 'U', the elements of the array AP corresponding to the diagonal elements of the matrix A are not referenced, but are assumed to be one.

- WORK (workspace) REAL array, dimension (MAX(1,LWORK)),

  where LWORK \>= N when NORM = 'I'; otherwise, WORK is not referenced.