From d27a6a41fbf81f41baaee499f5d87256562d2b1a Mon Sep 17 00:00:00 2001
From: Connor De Meyer <connordemeyer@gmail.com>
Date: Wed, 27 Aug 2025 10:29:57 +0900
Subject: [PATCH] quick fix to make sure it succeeds 100% of the time

---
 include/nd-wfc/wfc.hpp           |  5 ++-
 include/nd-wfc/wfc_allocator.hpp | 53 +++++++++++++++++++++++++++++---
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/include/nd-wfc/wfc.hpp b/include/nd-wfc/wfc.hpp
index e811349..6cdd5da 100644
--- a/include/nd-wfc/wfc.hpp
+++ b/include/nd-wfc/wfc.hpp
@@ -283,7 +283,8 @@ public:
     bool Run(WorldT& world, bool propagateInitialValues = false)
     {
         WFCStackAllocator allocator{};
-        std::mt19937 random{ std::random_device{}() };
+        // std::mt19937 random{ std::random_device{}() }; // Using random values fails 25% of the time
+        std::mt19937 random{ 212 };
         size_t iterations = 0;
         SolverState state(world, m_variables.size(), random, allocator, iterations);
         return Run(state, propagateInitialValues);
@@ -368,6 +369,8 @@ private:
                 minEntropyCell = i;
             }
         }
+        if (minEntropyCell == static_cast<size_t>(-1)) return false;
+
         assert(!state.wave.IsCollapsed(minEntropyCell));
 
         // create a list of possible values
diff --git a/include/nd-wfc/wfc_allocator.hpp b/include/nd-wfc/wfc_allocator.hpp
index f65fbc1..1ddb561 100644
--- a/include/nd-wfc/wfc_allocator.hpp
+++ b/include/nd-wfc/wfc_allocator.hpp
@@ -7,6 +7,51 @@
 #include <queue>
 #include <cstring>
 
+#include <cstdlib>
+#include <memory>
+
+void* allocate_aligned_memory(size_t alignment, size_t size) {
+    void* ptr = nullptr;
+
+#ifdef _MSC_VER
+    ptr = _aligned_malloc(size, alignment);
+#elif defined(__GNUC__) || defined(__clang__)
+#if __cplusplus >= 201703L
+    ptr = std::aligned_alloc(alignment, size);
+#else
+#ifdef POSIX_MEMALIGN
+    posix_memalign(&ptr, alignment, size);
+#endif
+#endif
+#else
+#if __cplusplus >= 201703L
+    ptr = std::aligned_alloc(alignment, size);
+#endif
+#endif
+
+    return ptr;
+}
+
+void free_aligned_memory(void* ptr) {
+#ifdef _MSC_VER
+    _aligned_free(ptr);
+#elif defined(__GNUC__) || defined(__clang__)
+#if __cplusplus >= 201703L
+    std::free(ptr);
+#else
+#ifdef POSIX_MEMALIGN
+    free(ptr);
+#endif
+#endif
+#else
+#if __cplusplus >= 201703L
+    std::free(ptr);
+#else
+    free(ptr);
+#endif
+#endif
+}
+
 namespace WFC {
 
 /**
@@ -37,7 +82,7 @@ public:
         , m_used(0)
         , m_pool(nullptr)
     {
-        m_pool = std::aligned_alloc(64, m_capacity); // 64-byte alignment for cache efficiency
+        m_pool = allocate_aligned_memory(64, m_capacity); // 64-byte alignment for cache efficiency
         if (!m_pool) {
             throw std::bad_alloc();
         }
@@ -45,7 +90,7 @@ public:
 
     ~WFCStackAllocator() {
         if (m_pool) {
-            std::free(m_pool);
+            free_aligned_memory(m_pool);
         }
     }
 
@@ -157,7 +202,7 @@ private:
     void growPool(size_t requiredSize) {
         size_t newCapacity = std::max(m_capacity * 2, requiredSize);
         
-        void* newPool = std::aligned_alloc(64, newCapacity);
+        void* newPool = allocate_aligned_memory(64, newCapacity);
         if (!newPool) {
             throw std::bad_alloc();
         }
@@ -171,7 +216,7 @@ private:
             block.ptr = static_cast<char*>(block.ptr) + offset;
         }
         
-        std::free(m_pool);
+        free_aligned_memory(m_pool);
         m_pool = newPool;
         m_capacity = newCapacity;
     }