## MA02CD

### Pertransposing the central band of a square matrix

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

Purpose

      To compute the pertranspose of a central band of a square matrix.

Specification

          SUBROUTINE MA02CD( N, KL, KU, A, LDA )
    C     .. Scalar Arguments ..
          INTEGER          KL, KU, LDA, N
    C     .. Array Arguments ..
          DOUBLE PRECISION A(LDA,*)

Arguments

Input/Output Parameters

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

      KL      (input) INTEGER
              The number of subdiagonals of A to be pertransposed.
              0 <= KL <= N-1.

      KU      (input) INTEGER
              The number of superdiagonals of A to be pertransposed.
              0 <= KU <= N-1.

      A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
              On entry, the leading N-by-N part of this array must
              contain a square matrix whose central band formed from
              the KL subdiagonals, the main diagonal and the KU
              superdiagonals will be pertransposed.
              On exit, the leading N-by-N part of this array contains
              the matrix A with its central band (the KL subdiagonals,
              the main diagonal and the KU superdiagonals) pertransposed
              (that is the elements of each antidiagonal appear in
              reversed order). This is equivalent to forming P*B'*P,
              where B is the matrix formed from the central band of A
              and P is a permutation matrix with ones down the secondary
              diagonal.

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

Further Comments

      None

Example

Program Text

      None

Program Data

      None

Program Results

      None

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