minus-eq.c
2.65 KB
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/* X - Y = k */
static int fd_minus_eq_filter(fd_constraint this)
{
fd_int x, y;
int k;
x = VAR(this, 0);
y = VAR(this, 1);
k = this->constants[0];
// XXX: just do bounds consistency, for now
if (_fd_var_del_lt(_fd_var_min(x) - k, y) |
_fd_var_del_gt(_fd_var_max(x) - k, y))
{
if (fd_domain_empty(y))
return FD_NOSOLUTION;
_fd_revise_connected(NULL, y);
}
if (_fd_var_del_lt(_fd_var_min(y) + k, x) |
_fd_var_del_gt(_fd_var_max(y) + k, x))
{
if (fd_domain_empty(x))
return FD_NOSOLUTION;
_fd_revise_connected(NULL, x);
}
return FD_OK;
}
int fd_minus_eq_propagate2(fd_constraint this, fd_int culprit)
{
fd_int revise;
int changed;
// XXX: just do bounds consistency, for now
if (culprit == VAR(this, 0))
{
revise = VAR(this, 1);
changed =
_fd_var_del_lt(_fd_var_min(culprit) - this->constants[0], revise);
changed |=
_fd_var_del_gt(_fd_var_max(culprit) - this->constants[0], revise);
}
else
{
revise = VAR(this, 0);
changed =
_fd_var_del_lt(_fd_var_min(culprit) + this->constants[0], revise);
changed |=
_fd_var_del_gt(_fd_var_max(culprit) + this->constants[0], revise);
}
if (changed && fd_domain_empty(revise))
return FD_NOSOLUTION;
if (changed)
_fd_revise_connected(NULL, revise);
return FD_OK;
}
int fd_minus_eq_propagate(fd_constraint this, fd_int revise)
{
fd_int other;
int idx;
int changed;
idx = revise == VAR(this, 0) ? 0 : 1;
other = VAR(this, 1 - idx);
// XXX: just do bounds consistency, for now
if (idx == 0)
{
changed =
_fd_var_del_lt(_fd_var_min(other) + this->constants[0], revise);
changed |=
_fd_var_del_gt(_fd_var_max(other) + this->constants[0], revise);
}
else
{
changed =
_fd_var_del_lt(_fd_var_min(other) - this->constants[0], revise);
changed |=
_fd_var_del_gt(_fd_var_max(other) - this->constants[0], 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_minus_eq(fd_int x, fd_int y, int k)
{
fd_constraint c = _fd_constraint_new(2, 1);
if (c)
{
c->variables[0] = FD_INT2C_VAR(x); c->variables[1] = FD_INT2C_VAR(y);
c->constants[0] = k;
#ifdef CONSTRAINT_CLASS
c->kind = FD_CONSTR_MINUS_EQ;
#else /* CONSTRAINT_CLASS */
c->propagator2 = fd_minus_eq_propagate2;
c->propagator = fd_minus_eq_propagate;
#endif /* CONSTRAINT_CLASS */
_fd_var_add_constraint(x, c);
_fd_var_add_constraint(y, c);
_fd_add_constraint(c);
}
return c;
}