var-eq-times.c
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/* X = Y * Z */
// XXX: assuming non-negative values
static int fd_var_eq_times_filter(fd_constraint this)
{
fd_int x, y, z;
int min_x, max_x, min_y, max_y, min_z, max_z;
int changed_x, changed_y, changed_z;
x = VAR(this, 0);
y = VAR(this, 1);
z = VAR(this, 2);
// XXX: just do (a kind of) bounds consistency, for now
min_x = _fd_var_min(x);
max_x = _fd_var_max(x);
min_z = _fd_var_min(z);
max_z = _fd_var_max(z);
if (max_z > 0)
changed_y = _fd_var_del_lt(min_x / max_z, y);
if (min_z > 0)
changed_y |= _fd_var_del_gt(max_x / min_z, y);
if (changed_y && fd_domain_empty(y))
{
return FD_NOSOLUTION;
_fd_revise_connected(NULL, y);
}
min_y = _fd_var_min(y);
max_y = _fd_var_max(y);
if (max_y > 0)
changed_z = _fd_var_del_lt(min_x / max_y, z);
if (min_y > 0)
changed_z |= _fd_var_del_gt(max_x / min_y, z);
if (changed_z && fd_domain_empty(z))
{
return FD_NOSOLUTION;
_fd_revise_connected(NULL, z);
min_z = _fd_var_min(z);
max_z = _fd_var_max(z);
}
changed_x = _fd_var_del_lt(min_y * min_z, x);
changed_x |= _fd_var_del_gt(max_y * max_z, x);
if (changed_x && fd_domain_empty(x))
{
return FD_NOSOLUTION;
_fd_revise_connected(NULL, x);
}
#if CONSTRAINT_TEMPS > 3
if (fd_var_single(x, 0) && fd_var_single(y, 0) && fd_var_single(z, 0))
fd__constraint_set_entailed(this);
#endif
return FD_OK;
}
int fd_var_eq_times_propagate2(fd_constraint this, fd_int culprit)
{
fd_int x, y, z;
int min_x, max_x, min_y, max_y, min_z, max_z;
int changed_x = 0, changed_y = 0, changed_z = 0;
x = VAR(this, 0);
y = VAR(this, 1);
z = VAR(this, 2);
// XXX: just do bounds consistency, for now
if (culprit == x)
{
min_x = _fd_var_min(x);
max_x = _fd_var_max(x);
min_z = _fd_var_min(z);
max_z = _fd_var_max(z);
if (max_z > 0)
changed_y = _fd_var_del_lt(min_x / max_z, y);
if (min_z > 0)
changed_y |= _fd_var_del_gt(max_x / min_z, y);
if (changed_y && fd_domain_empty(y))
return FD_NOSOLUTION;
min_y = _fd_var_min(y);
max_y = _fd_var_max(y);
if (max_y > 0)
changed_z = _fd_var_del_lt(min_x / max_y, z);
if (min_y > 0)
changed_z |= _fd_var_del_gt(max_x / min_y, z);
if (changed_z && fd_domain_empty(z))
return FD_NOSOLUTION;
}
else if (culprit == y) // culprit == y || culprit == z
{
min_y = _fd_var_min(y);
max_y = _fd_var_max(y);
min_z = _fd_var_min(z);
max_z = _fd_var_max(z);
changed_x = _fd_var_del_lt(min_y * min_z, x);
changed_x |= _fd_var_del_gt(max_y * max_z, x);
if (changed_x && fd_domain_empty(x))
return FD_NOSOLUTION;
min_x = _fd_var_min(x);
max_x = _fd_var_max(x);
if (max_y > 0)
changed_z = _fd_var_del_lt(min_x / max_y, z);
if (min_y > 0)
changed_z |= _fd_var_del_gt(max_x / min_y, z);
if (changed_z && fd_domain_empty(z))
return FD_NOSOLUTION;
}
else // culprit == z
{
min_y = _fd_var_min(y);
max_y = _fd_var_max(y);
min_z = _fd_var_min(z);
max_z = _fd_var_max(z);
changed_x = _fd_var_del_lt(min_y * min_z, x);
changed_x |= _fd_var_del_gt(max_y * max_z, x);
if (changed_x && fd_domain_empty(x))
return FD_NOSOLUTION;
min_x = _fd_var_min(x);
max_x = _fd_var_max(x);
if (max_z > 0)
changed_y = _fd_var_del_lt(min_x / max_z, y);
if (min_z > 0)
changed_y |= _fd_var_del_gt(max_x / min_z, y);
if (changed_y && fd_domain_empty(y))
return FD_NOSOLUTION;
}
if (changed_x)
_fd_revise_connected(NULL, x); // XXX: NULL or this?
if (changed_y)
_fd_revise_connected(NULL, y); // XXX: NULL or this?
if (changed_z)
_fd_revise_connected(NULL, z); // XXX: NULL or this?
#if CONSTRAINT_TEMPS > 3
if (fd_var_single(x, 0) && fd_var_single(y, 0) && fd_var_single(z, 0))
fd__constraint_set_entailed(this);
#endif
return FD_OK;
}
fd_constraint fd_var_eq_times(fd_int x, fd_int y, fd_int z)
{
fd_constraint c = _fd_constraint_new(3, 0);
if (c)
{
c->variables[0] = FD_INT2C_VAR(x);
c->variables[1] = FD_INT2C_VAR(y);
c->variables[2] = FD_INT2C_VAR(z);
#ifdef CONSTRAINT_CLASS
c->kind = FD_CONSTR_VAR_EQ_TIMES;
#else /* CONSTRAINT_CLASS */
c->propagator2 = fd_var_eq_times_propagate2;
#endif /* CONSTRAINT_CLASS */
_fd_var_add_constraint(x, c);
_fd_var_add_constraint(y, c);
_fd_var_add_constraint(z, c);
_fd_add_constraint(c);
}
return c;
}