5.2 MXMB: matrix-matrix product

      subroutine mxmb(a,mcola,mrowa,b,mcolb,mrowb,
     *r,mcolr,mrowr,ncol,nlink,nrow)
      implicit double precision (a-h,o-z)
      dimension r(1),a(1),b(1)

calculates the ${\tt ncol}\times{\tt nrow}$ matrix product $\bf R = R + A B$. Parameters are exactly as for mxma; the only difference is that r is not cleared to zero at the start, but the matrix product is added to the previous contents of r.