Add test showing bug in IsProbablyDuplicate()

src/crypto/equihash.cpp

@@ -317,28 +317,6 @@ bool Equihash<N,K>::BasicSolve(const eh_HashState& base_state,
     return false;
 }
 
-template<size_t MAX_INDICES>
-bool IsProbablyDuplicate(std::shared_ptr<eh_trunc> indices, size_t lenIndices)
-{
-    assert(lenIndices <= MAX_INDICES);
-    bool checked_index[MAX_INDICES] = {false};
-    bool count_checked = 0;
-    for (int z = 0; z < lenIndices; z++) {
-        // Skip over indices we have already paired
-        if (!checked_index[z]) {
-            for (int y = z+1; y < lenIndices; y++) {
-                if (!checked_index[y] && indices.get()[z] == indices.get()[y]) {
-                    // Pair found
-                    checked_index[y] = true;
-                    count_checked += 2;
-                    break;
-                }
-            }
-        }
-    }
-    return count_checked == lenIndices;
-}
-
 template<size_t WIDTH>
 void CollideBranches(std::vector<FullStepRow<WIDTH>>& X, const size_t hlen, const size_t lenIndices, const unsigned int clen, const unsigned int ilen, const eh_trunc lt, const eh_trunc rt)
 {

src/crypto/equihash.tcc

@@ -22,6 +22,28 @@ bool DistinctIndices(const FullStepRow<WIDTH>& a, const FullStepRow<WIDTH>& b, s
     return true;
 }
 
+template<size_t MAX_INDICES>
+bool IsProbablyDuplicate(std::shared_ptr<eh_trunc> indices, size_t lenIndices)
+{
+    assert(lenIndices <= MAX_INDICES);
+    bool checked_index[MAX_INDICES] = {false};
+    bool count_checked = 0;
+    for (int z = 0; z < lenIndices; z++) {
+        // Skip over indices we have already paired
+        if (!checked_index[z]) {
+            for (int y = z+1; y < lenIndices; y++) {
+                if (!checked_index[y] && indices.get()[z] == indices.get()[y]) {
+                    // Pair found
+                    checked_index[y] = true;
+                    count_checked += 2;
+                    break;
+                }
+            }
+        }
+    }
+    return count_checked == lenIndices;
+}
+
 template<size_t WIDTH>
 bool IsValidBranch(const FullStepRow<WIDTH>& a, const size_t len, const unsigned int ilen, const eh_trunc t)
 {

src/gtest/test_equihash.cpp

@@ -3,6 +3,16 @@
 
 #include "crypto/equihash.h"
 
+TEST(equihash_tests, is_probably_duplicate) {
+    std::shared_ptr<eh_trunc> p1 (new eh_trunc[4] {0, 1, 2, 3});
+    std::shared_ptr<eh_trunc> p2 (new eh_trunc[4] {0, 1, 1, 3});
+    std::shared_ptr<eh_trunc> p3 (new eh_trunc[4] {3, 1, 1, 3});
+
+    ASSERT_FALSE(IsProbablyDuplicate<4>(p1, 4));
+    ASSERT_FALSE(IsProbablyDuplicate<4>(p2, 4));
+    ASSERT_TRUE(IsProbablyDuplicate<4>(p3, 4));
+}
+
 TEST(equihash_tests, check_basic_solver_cancelled) {
     Equihash<48,5> Eh48_5;
     crypto_generichash_blake2b_state state;