anchor.diff:           p(i2) = v(i2) + sum
     20  continue  
   c     Solve the triangular system
  -c      call dtrsl(wt,m,col,p(col+1),11,info)
  -      call dpotrs('L',col,1,wt,m,p(col+1),col,info)
  +      call dtrsl(wt,m,col,p(col+1),11,info)
         if (info .ne. 0) return
    
   c     	solve D^(1/2)p1=v1.
  
positive.code: c        then form L^-1(-L_a'+R_z') in the (1,2) block.
        col2 = 2*col
        do 71 js = col+1 ,col2
  c         call dtrsl(wn,m2,col,wn(1,js),11,info)
           call dpotrs('L',col,1,wn,m2,wn(1,js),col,info)
    71  continue
  
  c     Form S'AA'S*theta + (L^-1(-L_a'+R_z'))'L^-1(-L_a'+R_z') in the
  
negative.code: c
  c     Subprograms called:
  c
  c       Linpack ... dpofa.
  c
  c
  