From f7a84fc77cba71fa2e93e2e3d8c1eaf8ff6fbdf8 Mon Sep 17 00:00:00 2001
From: "lperron@google.com"
 <lperron@google.com@59fed7e4-672f-1a80-1451-5ac2ff6d83f1>
Date: Sat, 9 Jun 2012 20:44:58 +0000
Subject: [PATCH] fix int modulo

---
 src/constraint_solver/constraints.cc | 34 +++++++++++++++++++---------
 1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/src/constraint_solver/constraints.cc b/src/constraint_solver/constraints.cc
index 8d41ec4532..c84894e3bb 100644
--- a/src/constraint_solver/constraints.cc
+++ b/src/constraint_solver/constraints.cc
@@ -822,19 +822,24 @@ class Modulo : public Constraint {
   }
 
   virtual void InitialPropagate() {
-    y_->SetRange(0, mod_ - 1);
-    to_remove_.clear();
-    for (x_iterator_->Init(); x_iterator_->Ok(); x_iterator_->Next()) {
-      const int64 value = x_iterator_->Value();
-      if (!y_->Contains(value % mod_)) {
-        to_remove_.push_back(value);
-      }
-    }
-    x_->RemoveValues(to_remove_);
-    to_remove_.clear();
-    if (y_->Size() == mod_) {
+    if (x_->Bound()) {
+      y_->SetValue(x_->Min() % mod_);
       return;
     }
+
+    y_->SetRange(0, mod_ - 1);
+    if (y_->Size() <= mod_) {
+      to_remove_.clear();
+      for (x_iterator_->Init(); x_iterator_->Ok(); x_iterator_->Next()) {
+        const int64 value = x_iterator_->Value();
+        if (!y_->Contains(value % mod_)) {
+          to_remove_.push_back(value);
+        }
+      }
+      x_->RemoveValues(to_remove_);
+      to_remove_.clear();
+    }
+
     for (y_iterator_->Init(); y_iterator_->Ok(); y_iterator_->Next()) {
       const int64 value = y_iterator_->Value();
       bool support = false;
@@ -851,6 +856,13 @@ class Modulo : public Constraint {
     y_->RemoveValues(to_remove_);
   }
 
+  virtual string DebugString() const {
+    return StringPrintf("(%s %% %" GG_LL_FORMAT "d == %s",
+                        x_->DebugString().c_str(),
+                        mod_,
+                        y_->DebugString().c_str());
+  }
+
  private:
   IntVar* const x_;
   IntVar* const y_;