Previous: dlansb Up: ../lapack-d.html Next: dlanst

dlansp

 NAME
      DLANSP - return the value of the one norm, or the Frobenius
      norm, or the infinity norm, or the element of largest abso-
      lute value of a real symmetric matrix A, supplied in packed
      form

 SYNOPSIS
      DOUBLE PRECISION FUNCTION DLANSP( NORM, UPLO, N, AP, WORK )

          CHARACTER    NORM, UPLO

          INTEGER      N

          DOUBLE       PRECISION AP( * ), WORK( * )

 PURPOSE
      DLANSP  returns the value of the one norm,  or the Frobenius
      norm, or the  infinity norm,  or the  element of  largest
      absolute value  of a real symmetric matrix A,  supplied in
      packed form.

 DESCRIPTION
      DLANSP returns the value

         DLANSP = ( 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  matrix norm.

 ARGUMENTS
      NORM    (input) CHARACTER*1
              Specifies the value to be returned in DLANSP as
              described above.

      UPLO    (input) CHARACTER*1
              Specifies whether the upper or lower triangular part
              of the symmetric matrix A is supplied.  = 'U':
              Upper triangular part of A is supplied
              = 'L':  Lower triangular part of A is supplied

      N       (input) INTEGER

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

      AP      (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
              The upper or lower triangle of the symmetric 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.

      WORK    (workspace) DOUBLE PRECISION array, dimension (LWORK),
              where LWORK >= N when NORM = 'I' or '1' or 'O'; oth-
              erwise, WORK is not referenced.