c     transpose a general double precision matrix.
      subroutine dgmtra (a,r,n,m)
      double precision a(1), r(1)
      ir=0
      do 10 i=1,n
      ij=i-n
      do 10 j=1,m
      ij=ij+n
      ir=ir+1
   10 r(ir)=a(ij)
      return
      end