Re: Is this code correct in the GMPL implementation ?

[Domingo Alvarez Duarte]

Hello !

This is my fourth time trying to replace the actual TUPLE struct 
representation https://github.com/mingodad/GLPK/tree/new-tuple and I'm 
struggling again in understand/rewrite some parts of the code, mainly 
src/mpl/mpl3.c::saturate_set and other places.

I'm asking for help to try to fix/rewrite the missing pieces on it, I 
hope that this changes once corrected would give a reduction in memory 
usage and probably execution time for GMPL.

Thank you in advance for any help you can give !

Cheers !

On 25/7/20 14:51, Andrew Makhorin wrote:
> On Sat, 2020-07-25 at 13:35 +0200, Domingo Alvarez Duarte wrote:
> > Hello !
> >
> > Trying to change the actual TUPLE structure by:
> >
> > ====
> >
> > #ifndef TUPLE_SIZE_T
> > #define TUPLE_SIZE_T int
> > #endif
> > struct TUPLE
> > {
> >         TUPLE_SIZE_T size;
> >         TUPLE_SIZE_T refcount;
> >         SYMBOL sym[1];
> >         /* symbol, which the component refers to; cannot be NULL */
> > };
> >
> > ====
> >
> > I found the code bellow (in src/mpl/mpl3.c) that I'm not sure I
> > understand it,
> >
> > it seems that it's only testing the last tuple against
> > "code->arg.arg.y", shouldn't it be testing inside the loop for every
> > tuple ?
> >
> > I would appreciate someone could help understand this code !
> >
> > ====
> >
> > int is_member(MPL *mpl, CODE *code, const TUPLE *tuple)
> > {     int value;
> > ...
> >
> >            case O_CROSS:
> >               {  int j;
> >                  value = is_member(mpl, code->arg.arg.x, tuple);
> >                  if (value)
> >                  {  for (j = 1; j <= code->arg.arg.x->dim; j++)
> >                     {  xassert(tuple != NULL);
> >                        tuple = tuple->next;
> >                     }
> >                     value = is_member(mpl, code->arg.arg.y, tuple);
> >                  }
> >               }
> >               break;
> >
> > ====
> >
> > Cheers !
> The routine is_member checks if the given n-tuple (specified by
> 'tuple') is a member of the given set (specified by 'code'). The check
> is performed recursively by traversing the set expression tree. For
> example, on evaluating the condition "... (x,y) in X cross Y ..." the
> routine will check that x is in X and y is in Y.