Shuffle signature hashing via random seed

Author: domschrei

src/data/htn_instance.cpp

@@ -15,6 +15,9 @@ HtnInstance::HtnInstance(Parameters& params) :
              _params(params), _p(*parse(params.getDomainFilename(), params.getProblemFilename())), 
             _share_q_constants(_params.isNonzero("sqq")) {
 
+    // Transfer random seed to the hash function for any kind of signature
+    USignatureHasher::seed = _params.getIntParam("s");
+
     Log::i("Parser finished.\n");
 
     Names::init(_name_back_table);

src/data/signature.cpp

@@ -85,3 +85,5 @@ Signature& Signature::operator=(Signature&& sig) {
     _negated = sig._negated;
     return *this;
 }
+
+int USignatureHasher::seed = 1;

src/data/signature.h

@@ -97,8 +97,9 @@ struct PositionedUSig {
 };
 
 struct USignatureHasher {
+    static int seed;
     inline std::size_t operator()(const USignature& s) const {
-        size_t hash = s._args.size();
+        size_t hash = seed + s._args.size();
         for (const int& arg : s._args) {
             hash_combine(hash, arg);
         }