MAX(1,N).

  B       (input/output) DOUBLE PRECISION array, dimension (LDB,M)
          On entry, the leading N-by-M part of this array must
          contain the system input matrix B.
          On exit, the leading N-by-M part of this array contains
          the transformed matrix P*B.

  LDB     INTEGER
          The leading dimension of the array B.
          LDB &gt;= MAX(1,N) if M &gt; 0.
          LDB &gt;= 1        if M = 0.

  C       (input/output) DOUBLE PRECISION array, dimension (LDC,N)
      