nogoods.c
1.35 KB
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#include <string.h>
/* binary constraint (between X and Y) defined through the disallowed pairs */
int fd_nogoods_propagate(fd_constraint this, fd_int revise)
{
fd_int other;
int rx, ox; // variables' indexes within the constraint
int value;
int changed = 0;
int i;
rx = revise == VAR(this, 0) ? 0 : 1;
ox = 1 - rx;
other = VAR(this, ox);
// only propagate if other's domain is a singleton
if (!fd_var_single(other, &value))
return FD_OK;
for (i = 0; i < this->nconstants; i += 2)
if (this->constants[i + ox] == value)
changed |= _fd_var_del_val(this->constants[i + rx], revise);
if (changed && fd_domain_empty(revise))
return FD_NOSOLUTION;
// XXX: enqueue further updates here?
if (changed)
_fd_revise_connected(this, revise);
return FD_OK;
}
fd_constraint fd_nogoods(fd_int x, fd_int y, int *nogoods, int nnogoods)
{
fd_constraint c = _fd_constraint_new(2, 2 * nnogoods);
if (c)
{
c->variables[0] = FD_INT2C_VAR(x); c->variables[1] = FD_INT2C_VAR(y);
#ifdef CONSTRAINT_CLASS
c->kind = FD_CONSTR_NOGOODS;
#else /* CONSTRAINT_CLASS */
c->propagator = fd_nogoods_propagate;
#endif /* CONSTRAINT_CLASS */
memcpy(c->constants, nogoods, 2 * nnogoods * sizeof(int));
_fd_var_add_constraint(x, c);
_fd_var_add_constraint(y, c);
_fd_add_constraint(c);
}
return c;
}