maxima is more than 500 times slower than maple



> My guess is that you are doing a vastly different computation, perhaps 
> repeating unnecessary simplifications,
> in your Maxima specifications.  Nevertheless, the Maple computation 
> would ordinarily be somewhat faster.
>
> I'm not sure what you wish to accomplish by expand()  or ratsimp.
>
> For example, expand((a+b+c+d)^30)  takes 0.83 seconds but 
> rat((a+b+c+d)^30)  takes 0.05 seconds.
>
> I think that Valery Pipin's response excludes the (commented out) 
> long-running command at the end.
Indeed, that is right. If it is included
calculation is finished  with ldb :
                                 0
(%i21) ddelta : ratsimp(subst([SK4uu[b,a]=SK4uu[a,b], 
SK4uu[c,a]=SK4uu[a,c], SK4uu[c,b]=SK4uu[b,c]], ddelta))$
Heap exhausted during garbage collection: 0 bytes available, 16 requested.
  Gen StaPg UbSta LaSta LUbSt Boxed Unboxed LB   LUB  !move  Alloc 
Waste   Trig    WP  GCs Mem-age
    0:     0     0     0     0     0     0     0     0     0 0     0 
10737418    0   0  0.0000
   .....