[gecode-users] Expr() in GECODE

[Zhu Zichen's cse]

Hi,

I have a question.
For GECODE,
When I use expressions:
     BoolVar sofar = expr( home,( !_A[i]   ||   x[index] != val ));// where
_A[i] is a BoolVar, and x is IntVarArray, index and val are integer.

If I rewrite it as:
     if(_A[i].one())
      sofar = expr( home, x[index] != val);
     else
      sofar = expr( home,( !_A[i]   ||   x[index] != val));
There will be a great improvement on runtime, say 40%.

If I rewrite it as:
   if(_A[i].one())
     x[index].nq(val);
   else
    sofar = expr( home,( !_A[i]   ||   x[index] != val));
There will be another improvement on the latest one for runtime, say 30%.


For ILOG,
 IlcConstraint sofar =   (! _A[i]) ||     x[index] != val ) ;

Rewrite as:
     if(_A[i].isTrue()==IlcTrue)
        sofar = x[index] != val;
    else
       sofar =   (! _A[i]) ||     x[index] != val ) ;
Running times of the above two methods are the same.



Is this because the "inefficient" of expr() to handle  Boolean expressions
and relations in GECODE?


Thanks!

Zichen

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