diff --git a/src/codeobject.h b/src/codeobject.h
index 6ae0b7d8..1f7cc095 100644
--- a/src/codeobject.h
+++ b/src/codeobject.h
@@ -64,6 +64,8 @@ struct CodeObject {
     std::map<StrName, int> global_names;
     std::vector<CodeBlock> blocks = { CodeBlock{NO_BLOCK, -1} };
     std::map<StrName, int> labels;
+    
+    int recommended_hashmap_capacity = 8;
 
     void optimize(VM* vm);
 
diff --git a/src/common.h b/src/common.h
index b1112583..7e37c9cf 100644
--- a/src/common.h
+++ b/src/common.h
@@ -24,6 +24,7 @@
 #include <functional>
 #include <iostream>
 #include <map>
+#include <algorithm>
 // #include <filesystem>
 // namespace fs = std::filesystem;
 
@@ -64,4 +65,6 @@ struct Type {
 //#define THREAD_LOCAL thread_local
 #define THREAD_LOCAL
 
-#define RAW(T) std::remove_const_t<std::remove_reference_t<T>>
\ No newline at end of file
+#define RAW(T) std::remove_const_t<std::remove_reference_t<T>>
+
+const float kNameDictLoadFactor = 0.8;
\ No newline at end of file
diff --git a/src/namedict.h b/src/namedict.h
new file mode 100644
index 00000000..4eebad21
--- /dev/null
+++ b/src/namedict.h
@@ -0,0 +1,154 @@
+#pragma once
+
+#include "safestl.h"
+
+struct NameDictNode{
+    StrName first;
+    PyVar second;
+    inline bool empty() const { return first.empty(); }
+};
+
+struct NameDict {
+    int _capacity;
+    int _size;
+    NameDictNode* _a;
+
+    NameDict(int capacity=2): _capacity(capacity), _size(0) {
+        _a = new NameDictNode[_capacity];
+    }
+
+    NameDict(const NameDict& other) {
+        this->_capacity = other._capacity;
+        this->_size = other._size;
+        this->_a = new NameDictNode[_capacity];
+        for(int i=0; i<_capacity; i++) _a[i] = other._a[i];
+    }
+    
+    NameDict& operator=(const NameDict& other){
+        delete[] _a;
+        this->_capacity = other._capacity;
+        this->_size = other._size;
+        this->_a = new NameDictNode[_capacity];
+        for(int i=0; i<_capacity; i++) _a[i] = other._a[i];
+        return *this;
+    }
+
+    NameDict(NameDict&&) = delete;
+    NameDict& operator=(NameDict&&) = delete;
+
+    int size() const { return _size; }
+
+#define HASH_PROBE(key, ok, i) \
+    int i = (key).index % _capacity; \
+    bool ok = false; \
+    while(!_a[i].empty()) { \
+        if(_a[i].first == (key)) { ok = true; break; } \
+        i = (i + 1) % _capacity; \
+    }
+
+#define HASH_PROBE_OVERRIDE(key, ok, i) \
+    i = (key).index % _capacity; \
+    ok = false; \
+    while(!_a[i].empty()) { \
+        if(_a[i].first == (key)) { ok = true; break; } \
+        i = (i + 1) % _capacity; \
+    }
+
+    const PyVar& operator[](StrName key) const {
+        HASH_PROBE(key, ok, i);
+        if(!ok) throw std::out_of_range("NameDict key not found");
+        return _a[i].second;
+    }
+
+    [[nodiscard]] PyVar& operator[](StrName key){
+        HASH_PROBE(key, ok, i);
+        if(!ok) {
+            _a[i].first = key;
+            _size++;
+            if(_size > _capacity * kNameDictLoadFactor){
+                __rehash_2x();
+                HASH_PROBE_OVERRIDE(key, ok, i);
+            }
+        }
+        return _a[i].second;
+    }
+
+    void __rehash_2x(){
+        NameDictNode* old_a = _a;
+        int old_capacity = _capacity;
+        _capacity *= 2;
+        _size = 0;
+        _a = new NameDictNode[_capacity];
+        for(int i=0; i<old_capacity; i++){
+            if(old_a[i].empty()) continue;
+            HASH_PROBE(old_a[i].first, ok, j);
+            _a[j].first = old_a[i].first;
+            _a[j].second = std::move(old_a[i].second);
+            _size++;
+        }
+        delete[] old_a;
+    }
+
+    inline PyVar* try_get(StrName key){
+        HASH_PROBE(key, ok, i);
+        if(!ok) return nullptr;
+        return &_a[i].second;
+    }
+
+    inline bool contains(StrName key) const {
+        HASH_PROBE(key, ok, i);
+        return ok;
+    }
+
+    ~NameDict(){ delete[] _a;}
+
+    struct iterator {
+        const NameDict* _dict;
+        int i;
+        iterator() = default;
+        iterator(const NameDict* dict, int i): _dict(dict), i(i) { _skip_empty(); }
+        inline void _skip_empty(){ while(i < _dict->_capacity && _dict->_a[i].empty()) i++;}
+        inline iterator& operator++(){ i++; _skip_empty(); return *this;}
+
+        inline bool operator!=(const iterator& other) const { return i != other.i; }
+        inline bool operator==(const iterator& other) const { return i == other.i; }
+
+        inline NameDictNode* operator->() const { return &_dict->_a[i]; }
+    };
+
+    template<typename T>
+    void emplace(StrName key, T&& value){
+        HASH_PROBE(key, ok, i);
+        if(!ok) {
+            _a[i].first = key;
+            _size++;
+            if(_size > _capacity * kNameDictLoadFactor){
+                __rehash_2x();
+                HASH_PROBE_OVERRIDE(key, ok, i);
+            }
+        }
+        _a[i].second = std::forward<T>(value);
+    }
+
+    void insert(iterator begin, iterator end){
+        for(auto it = begin; it != end; ++it){
+            emplace(it->first, it->second);
+        }
+    }
+
+    iterator find(StrName key) const{
+        HASH_PROBE(key, ok, i);
+        if(!ok) return end();
+        return iterator(this, i);
+    }
+
+    void erase(StrName key){
+        HASH_PROBE(key, ok, i);
+        if(!ok) throw std::out_of_range("NameDict key not found");
+        _a[i] = NameDictNode();
+        _size--;
+    }
+
+    inline iterator begin() const { return iterator(this, 0); }
+    inline iterator end() const { return iterator(this, _capacity); }
+};
\ No newline at end of file
diff --git a/src/safestl.h b/src/safestl.h
index f8fa0256..6485f105 100644
--- a/src/safestl.h
+++ b/src/safestl.h
@@ -11,39 +11,33 @@ typedef PyVar PyVarRef;
 
 #include "hash_table5.hpp"
 namespace pkpy {
-	template<typename... Args>
-	using HashMap = emhash5::HashMap<Args...>;
-}
+    #include "namedict.h"
+	// template<typename... Args>
+	// using HashMap = emhash5::HashMap<Args...>;
+    // typedef HashMap<StrName, PyVar> NameDict;
+    
+    class List: public std::vector<PyVar> {
+        PyVar& at(size_t) = delete;
 
-namespace pkpy{
-class List: public std::vector<PyVar> {
-    PyVar& at(size_t) = delete;
-
-    inline void _check_index(size_t i) const {
-        if (i >= size()){
-            auto msg = "std::vector index out of range, " + std::to_string(i) + " not in [0, " + std::to_string(size()) + ")";
-            throw std::out_of_range(msg);
+        inline void _check_index(size_t i) const {
+            if (i >= size()){
+                auto msg = "std::vector index out of range, " + std::to_string(i) + " not in [0, " + std::to_string(size()) + ")";
+                throw std::out_of_range(msg);
+            }
+        }
+    public:
+        PyVar& operator[](size_t i) {
+            _check_index(i);
+            return std::vector<PyVar>::operator[](i);
         }
-    }
-public:
-    PyVar& operator[](size_t i) {
-        _check_index(i);
-        return std::vector<PyVar>::operator[](i);
-    }
 
-    const PyVar& operator[](size_t i) const {
-        _check_index(i);
-        return std::vector<PyVar>::operator[](i);
-    }
+        const PyVar& operator[](size_t i) const {
+            _check_index(i);
+            return std::vector<PyVar>::operator[](i);
+        }
 
-    using std::vector<PyVar>::vector;
-};
-
-
-}
-
-namespace pkpy {
-    typedef HashMap<StrName, PyVar> NameDict;
+        using std::vector<PyVar>::vector;
+    };
 
     class Args {
         static THREAD_LOCAL SmallArrayPool<PyVar, 10> _pool;
@@ -140,8 +134,5 @@ namespace pkpy {
     }
 
     typedef Args Tuple;
-
-    // declare static members
     THREAD_LOCAL SmallArrayPool<PyVar, 10> Args::_pool;
-    // THREAD_LOCAL SmallArrayPool<NameDictNode, 1> NameDict::_pool;
 }   // namespace pkpy
\ No newline at end of file
diff --git a/src/str.h b/src/str.h
index 8cfb72a0..3b56096b 100644
--- a/src/str.h
+++ b/src/str.h
@@ -140,7 +140,6 @@ struct StrName {
     StrName(const Str& s): index(get(s).index) {}
     inline const Str& str() const { return _r_interned[index]; }
     inline bool empty() const { return index == -1; }
-    inline void reset() { index = -1; }
 
     inline bool operator==(const StrName& other) const noexcept {
         return this->index == other.index;
diff --git a/src/vm.h b/src/vm.h
index 8db5c15c..7adcfe17 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -25,7 +25,7 @@ public:
 
     pkpy::NameDict _types;
     pkpy::NameDict _modules;                            // loaded modules
-    pkpy::HashMap<StrName, Str> _lazy_modules;       // lazy loaded modules
+    std::map<StrName, Str> _lazy_modules;       // lazy loaded modules
     PyVar None, True, False, Ellipsis;
 
     bool use_stdio;
@@ -151,7 +151,7 @@ public:
             return f(this, args);
         } else if(is_type(*callable, tp_function)){
             const pkpy::Function& fn = PyFunction_AS_C(*callable);
-            pkpy::shared_ptr<pkpy::NameDict> _locals = pkpy::make_shared<pkpy::NameDict>();
+            auto _locals = pkpy::make_shared<pkpy::NameDict>(fn.code->recommended_hashmap_capacity);
             pkpy::NameDict& locals = *_locals;
 
             int i = 0;
@@ -172,7 +172,7 @@ public:
             }else{
                 for(StrName key : fn.kwargs_order){
                     if(i < args.size()){
-                        locals[key] = args[i++];
+                        locals.emplace(key, args[i++]);
                     }else{
                         break;
                     }
@@ -185,8 +185,7 @@ public:
                 if(!fn.kwargs.contains(key)){
                     TypeError(key.escape(true) + " is an invalid keyword argument for " + fn.name + "()");
                 }
-                const PyVar& val = kwargs[i+1];
-                locals[key] = val;
+                locals.emplace(key, kwargs[i+1]);
             }
             PyVar _module = fn._module != nullptr ? fn._module : top_frame()->_module;
             auto _frame = _new_frame(fn.code, _module, _locals, fn._closure);
@@ -212,10 +211,12 @@ public:
         }catch (const pkpy::Exception& e){
             *_stderr << e.summary() << '\n';
         }
+#ifdef _NDEBUG
         catch (const std::exception& e) {
             *_stderr << "An std::exception occurred! It could be a bug.\n";
             *_stderr << e.what() << '\n';
         }
+#endif
         callstack = {};
         return nullptr;
     }
@@ -857,6 +858,11 @@ PyVar pkpy::NativeFunc::operator()(VM* vm, pkpy::Args& args) const{
 }
 
 void CodeObject::optimize(VM* vm){
+    int n = 0;
+    for(auto& p: names) if(p.second == NAME_LOCAL) n++;
+    recommended_hashmap_capacity = (int)(n / kNameDictLoadFactor + 1.5);
+    if(recommended_hashmap_capacity < 2) recommended_hashmap_capacity = 2;
+
     for(int i=1; i<codes.size(); i++){
         if(codes[i].op == OP_UNARY_NEGATIVE && codes[i-1].op == OP_LOAD_CONST){
             codes[i].op = OP_NO_OP;