## MA02BD

### Reversing the order of rows and/or columns of a matrix

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

      To reverse the order of rows and/or columns of a given matrix A
      by pre-multiplying and/or post-multiplying it, respectively, with
      a permutation matrix P, where P is a square matrix of appropriate
      order, with ones down the secondary diagonal.

Specification

          SUBROUTINE MA02BD( SIDE, M, N, A, LDA )
    C     .. Scalar Arguments ..
          CHARACTER          SIDE
          INTEGER            LDA, M, N
    C     .. Array Arguments ..
          DOUBLE PRECISION   A(LDA,*)

Arguments

Mode Parameters

      SIDE    CHARACTER*1
              Specifies the operation to be performed, as follows:
              = 'L': the order of rows of A is to be reversed by
                     pre-multiplying A with P;
              = 'R': the order of columns of A is to be reversed by
                     post-multiplying A with P;
              = 'B': both the order of rows and the order of columns
                     of A is to be reversed by pre-multiplying and
                     post-multiplying A with P.

Input/Output Parameters

      M       (input) INTEGER
              The number of rows of the matrix A.  M >= 0.

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

      A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
              On entry, the leading M-by-N part of this array must
              contain the given matrix whose rows and/or columns are to
              be permuted.
              On exit, the leading M-by-N part of this array contains
              the matrix P*A if SIDE = 'L', or A*P if SIDE = 'R', or
              P*A*P if SIDE = 'B'.

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

Further Comments

      None

Example

Program Text

      None

Program Data

      None

Program Results

      None

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