diff --git a/CMakeLists.txt b/CMakeLists.txt
index 00f2f30..d3d5f2c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.25)
-project(blt-gp VERSION 0.1.19)
+project(blt-gp VERSION 0.1.20)
 
 include(CTest)
 
diff --git a/examples/symbolic_regression.cpp b/examples/symbolic_regression.cpp
index d9c0b05..f620edd 100644
--- a/examples/symbolic_regression.cpp
+++ b/examples/symbolic_regression.cpp
@@ -113,6 +113,7 @@ int main()
     while (!program.should_terminate())
     {
         BLT_TRACE("------------{Begin Generation %ld}------------", program.get_current_generation());
+        BLT_TRACE("Creating next generation");
         BLT_START_INTERVAL("Symbolic Regression", "Gen");
         program.create_next_generation();
         BLT_END_INTERVAL("Symbolic Regression", "Gen");
@@ -148,5 +149,12 @@ int main()
     
     BLT_PRINT_PROFILE("Symbolic Regression", blt::PRINT_CYCLES | blt::PRINT_THREAD | blt::PRINT_WALL);
     
+//    BLT_TRACE("Allocations:");
+//    auto h = static_cast<blt::ptrdiff_t>(blt::gp::hello.load());
+//    auto u = static_cast<blt::ptrdiff_t>(blt::gp::unhello.load());
+//    BLT_TRACE("Allocated: %ld", h);
+//    BLT_TRACE("Deallocated: %ld", u);
+//    BLT_TRACE("Ratio: %lf Difference: %ld", static_cast<double>(h) / static_cast<double>(u), std::abs(h - u));
+    
     return 0;
 }
\ No newline at end of file
diff --git a/include/blt/gp/fwdecl.h b/include/blt/gp/fwdecl.h
index c058d5a..2c41f91 100644
--- a/include/blt/gp/fwdecl.h
+++ b/include/blt/gp/fwdecl.h
@@ -55,7 +55,7 @@ namespace blt::gp
         class operator_storage_test;
         // context*, read stack, write stack
         using operator_func_t = std::function<void(void*, stack_allocator&, stack_allocator&)>;
-        using eval_func_t = std::function<evaluation_context(const tree_t& tree, void* context)>;
+        using eval_func_t = std::function<evaluation_context&(const tree_t& tree, void* context)>;
         // debug function,
         using print_func_t = std::function<void(std::ostream&, stack_allocator&)>;
         
diff --git a/include/blt/gp/program.h b/include/blt/gp/program.h
index 8a87553..69e52cf 100644
--- a/include/blt/gp/program.h
+++ b/include/blt/gp/program.h
@@ -115,12 +115,14 @@ namespace blt::gp
                 for (auto v : sizes)
                     largest = std::max(v, largest);
                 
-                storage.eval_func = [&operators..., largest](const tree_t& tree, void* context) {
+                storage.eval_func = [&operators..., largest](const tree_t& tree, void* context) -> evaluation_context& {
                     const auto& ops = tree.get_operations();
                     const auto& vals = tree.get_values();
                     
-                    evaluation_context results{};
+                    static thread_local evaluation_context results{};
+                    results.values.reset();
                     results.values.reserve(largest);
+//                    BLT_DEBUG("%ld stored %ld", largest, results.values.internal_storage_size());
                     
                     blt::size_t total_so_far = 0;
                     
@@ -261,7 +263,7 @@ namespace blt::gp
                 storage.names.push_back(op.get_name());
                 if (op.is_ephemeral())
                     storage.static_types.insert(operator_id);
-                return total_size_required;
+                return total_size_required * 2;
             }
             
             template<typename T>
diff --git a/include/blt/gp/stack.h b/include/blt/gp/stack.h
index 21668eb..d2e4fe3 100644
--- a/include/blt/gp/stack.h
+++ b/include/blt/gp/stack.h
@@ -20,7 +20,7 @@
 #define BLT_GP_STACK_H
 
 #include <blt/std/types.h>
-#include <blt/std/atomic_allocator.h>
+#include <blt/std/bump_allocator.h>
 #include <blt/std/assert.h>
 #include <blt/std/logging.h>
 #include <blt/std/allocator.h>
@@ -43,16 +43,25 @@ namespace blt::gp
         BLT_META_MAKE_FUNCTION_CHECK(drop);
     }
     
+//    inline std::atomic_uint64_t hello = 0;
+//    inline std::atomic_uint64_t unhello = 0;
+    
     class aligned_allocator
     {
         public:
             void* allocate(blt::size_t bytes) // NOLINT
             {
+//                hello.fetch_add(1, std::memory_order_relaxed);
+//                BLT_TRACE("Allocating %ld bytes", bytes);
                 return std::aligned_alloc(8, bytes);
             }
             
             void deallocate(void* ptr, blt::size_t) // NOLINT
             {
+//                if (ptr == nullptr)
+//                    return;
+//                unhello.fetch_add(1, std::memory_order_relaxed);
+//                BLT_TRACE("Deallocating %ld bytes", bytes);
                 std::free(ptr);
             }
     };
@@ -122,7 +131,6 @@ namespace blt::gp
             
             ~stack_allocator()
             {
-                //std::free(data_);
                 get_allocator().deallocate(data_, size_);
             }
             
@@ -266,13 +274,33 @@ namespace blt::gp
             void reserve(blt::size_t bytes)
             {
                 if (bytes > size_)
-                    expand(bytes);
+                    expand_raw(bytes);
+            }
+            
+            [[nodiscard]] blt::size_t stored() const
+            {
+                return bytes_stored;
+            }
+            
+            [[nodiscard]] blt::size_t internal_storage_size() const
+            {
+                return size_;
+            }
+            
+            void reset()
+            {
+                bytes_stored = 0;
             }
         
         private:
             void expand(blt::size_t bytes)
             {
                 bytes = to_nearest_page_size(bytes);
+                expand_raw(bytes);
+            }
+            
+            void expand_raw(blt::size_t bytes)
+            {
                 auto new_data = static_cast<blt::u8*>(get_allocator().allocate(bytes));
                 if (bytes_stored > 0)
                     std::memcpy(new_data, data_, bytes_stored);
diff --git a/include/blt/gp/tree.h b/include/blt/gp/tree.h
index 96dedfa..8045428 100644
--- a/include/blt/gp/tree.h
+++ b/include/blt/gp/tree.h
@@ -84,7 +84,7 @@ namespace blt::gp
                 return values;
             }
             
-            evaluation_context evaluate(void* context) const
+            evaluation_context& evaluate(void* context) const
             {
                 return (*func)(*this, context);
             }
@@ -115,7 +115,7 @@ namespace blt::gp
             template<typename T>
             T get_evaluation_value(void* context)
             {
-                auto results = evaluate(context);
+                auto& results = evaluate(context);
                 return results.values.pop<T>();
             }