Jip J. Dekker
35a3110598
git-subtree-dir: software/chuffed git-subtree-split: 2ed0c01558d2a5c49c1ce57e048d32c17adf92d3
125 lines
2.7 KiB
C++
125 lines
2.7 KiB
C++
#include <chuffed/core/propagator.h>
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// y = min(x_i)
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// Bounds propagator, not fully consistent
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template <int U>
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class Minimum : public Propagator, public Checker {
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public:
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int const sz;
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IntView<U> * const x;
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IntView<U> const y;
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// Persistent state
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Tint min_max_var;
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Tint64_t min_max;
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Tint64_t min_fixed;
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// Intermediate state
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bool lower_change;
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Minimum(vec<IntView<U> > _x, IntView<U> _y) :
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sz(_x.size()), x(_x.release()), y(_y), min_max_var(-1), min_max(INT_MAX),
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min_fixed(INT_MAX), lower_change(false) {
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priority = 1;
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for (int i = 0; i < sz; i++) x[i].attach(this, i, EVENT_LU);
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y.attach(this, sz, EVENT_L);
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}
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void wakeup(int i, int c) {
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if (i < sz) {
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if (c & EVENT_F) {
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int64_t m = x[i].getVal();
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if (m < min_fixed) min_fixed = m;
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}
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int64_t m = x[i].getMax();
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if (m < min_max) {
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min_max_var = i;
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min_max = m;
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pushInQueue();
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}
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}
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if (c & y.getEvent(EVENT_L)) {
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lower_change = true;
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pushInQueue();
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}
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}
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bool propagate() {
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// make a less than or equal to min(max(x_i))
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setDom(y, setMax, min_max, x[min_max_var].getMaxLit());
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if (lower_change) {
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// make a greater than or equal to min(min(b_i))
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int64_t m = INT64_MAX;
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for (int i = 0; i < sz; i++) {
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int64_t t = x[i].getMin();
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if (t < m) m = t;
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}
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if (y.setMinNotR(m)) {
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Clause *r = NULL;
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if (so.lazy) {
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r = Reason_new(sz+1);
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// Finesse lower bounds
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// Add reason ![y <= m-1] \/ [x_1 <= m-1] \/ ... \/ [x_n <= m-1]
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for (int i = 0; i < sz; i++) (*r)[i+1] = x[i].getFMinLit(m);
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// for (int i = 0; i < sz; i++) (*r)[i+1] = x[i].getLit(m-1, 3);
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}
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if (!y.setMin(m, r)) return false;
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}
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// make b_i greater than or equal to min(a)
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m = y.getMin();
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Clause *r = NULL;
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if (so.lazy) {
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r = Reason_new(2);
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(*r)[1] = y.getMinLit();
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}
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for (int i = 0; i < sz; i++) {
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if (x[i].setMinNotR(m)) if (!x[i].setMin(m, r)) return false;
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}
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}
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// Necessary and sufficient conditions for redundancy
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if (y.getMin() == min_max) satisfied = true;
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return true;
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}
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void clearPropState() {
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in_queue = false;
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lower_change = false;
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}
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bool check() {
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int min = INT_MAX;
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for (int i = 0; i < sz; i++) if (x[i].getShadowVal() < min) min = x[i].getShadowVal();
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return (y.getShadowVal() == min);
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}
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int checkSatisfied() {
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if (satisfied) return 1;
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if (y.getMin() == min_max) satisfied = true;
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return 2;
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}
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};
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void minimum(vec<IntVar*>& x, IntVar* y) {
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vec<IntView<> > w;
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for (int i = 0; i < x.size(); i++) w.push(IntView<>(x[i]));
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new Minimum<0>(w, IntView<>(y));
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}
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void maximum(vec<IntVar*>& x, IntVar* y) {
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vec<IntView<> > w;
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for (int i = 0; i < x.size(); i++) w.push(IntView<>(x[i]));
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new Minimum<1>(w, IntView<>(y));
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}
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