MA02DD

Pack/unpack the upper or lower triangle of a symmetric matrix

Purpose

  To pack/unpack the upper or lower triangle of a symmetric matrix.
  The packed matrix is stored column-wise in the one-dimensional
  array AP.

      SUBROUTINE MA02DD( JOB, UPLO, N, A, LDA, AP )
C     .. Scalar Arguments ..
      CHARACTER          JOB, UPLO
      INTEGER            LDA, N
C     .. Array Arguments ..
      DOUBLE PRECISION   A(LDA,*), AP(*)

Mode Parameters

  JOB     CHARACTER*1
          Specifies whether the matrix should be packed or unpacked,
          as follows:
          = 'P':  The matrix should be packed;
          = 'U':  The matrix should be unpacked.

  UPLO    CHARACTER*1
          Specifies the part of the matrix to be packed/unpacked,
          as follows:
          = 'U':  Upper triangular part;
          = 'L':  Lower triangular part.

  N       (input) INTEGER
          The order of the matrix A.  N >= 0.

  A       (input or output) DOUBLE PRECISION array, dimension
          (LDA,N)
          This array is an input parameter if JOB = 'P', and an
          output parameter if JOB = 'U'.
          On entry, if JOB = 'P', the leading N-by-N upper
          triangular part (if UPLO = 'U'), or lower triangular part
          (if UPLO = 'L'), of this array must contain the
          corresponding upper or lower triangle of the symmetric
          matrix A, and the other strictly triangular part is not
          referenced.
          On exit, if JOB = 'U', the leading N-by-N upper triangular
          part (if UPLO = 'U'), or lower triangular part (if
          UPLO = 'L'), of this array contains the corresponding
          upper or lower triangle of the symmetric matrix A; the
          other strictly triangular part is not referenced.

  LDA     INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).

  AP      (output or input) DOUBLE PRECISION array, dimension
          (N*(N+1)/2)
          This array is an output parameter if JOB = 'P', and an
          input parameter if JOB = 'U'.
          On entry, if JOB = 'U', the leading N*(N+1)/2 elements of
          this array must contain the upper (if UPLO = 'U') or lower
          (if UPLO = 'L') triangle of the symmetric matrix A, packed
          column-wise. That is, the elements are stored in the order
          11, 12, 22, ..., 1n, 2n, 3n, ..., nn,      if UPLO = 'U';
          11, 21, 31, ..., n1, 22, 32, ..., n2, ..., if UPLO = 'L'.
          On exit, if JOB = 'P', the leading N*(N+1)/2 elements of
          this array contain the upper (if UPLO = 'U') or lower
          (if UPLO = 'L') triangle of the symmetric matrix A, packed
          column-wise, as described above.

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Program Text

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