Avoid dict resizing while creating fixed-size dicts.

Cython/Compiler/ExprNodes.py

@@ -8471,8 +8471,9 @@ class DictNode(ExprNode):
         if is_dict:
             self.release_errors()
             code.putln(
-                "%s = PyDict_New(); %s" % (
+                "%s = __Pyx_PyDict_NewPresized(%d); %s" % (
                     self.result(),
+                    len(self.key_value_pairs),
                     code.error_goto_if_null(self.result(), self.pos)))
             code.put_gotref(self.py_result())
 

Cython/Compiler/PyrexTypes.py

@@ -3167,7 +3167,8 @@ class ToPyStructUtilityCode(object):
         code.putln("%s {" % self.header)
         code.putln("PyObject* res;")
         code.putln("PyObject* member;")
-        code.putln("res = PyDict_New(); if (unlikely(!res)) return NULL;")
+        code.putln("res = __Pyx_PyDict_NewPresized(%d); if (unlikely(!res)) return NULL;" %
+                   len(self.type.scope.var_entries))
         for member in self.type.scope.var_entries:
             nameconst_cname = code.get_py_string_const(member.name, identifier=True)
             code.putln("%s; if (unlikely(!member)) goto bad;" % (

Cython/Utility/Coroutine.c

@@ -1742,7 +1742,7 @@ static PyObject* __Pyx_Coroutine_patch_module(PyObject* module, const char* py_c
 #if defined(__Pyx_Generator_USED) || defined(__Pyx_Coroutine_USED)
     int result;
     PyObject *globals, *result_obj;
-    globals = PyDict_New();  if (unlikely(!globals)) goto ignore;
+    globals = __Pyx_PyDict_NewPresized(4);  if (unlikely(!globals)) goto ignore;
     result = PyDict_SetItemString(globals, "_cython_coroutine_type",
     #ifdef __Pyx_Coroutine_USED
         (PyObject*)__pyx_CoroutineType);

Cython/Utility/ModuleSetupCode.c

@@ -255,6 +255,12 @@
   #define __Pyx_PyThreadState_Current _PyThreadState_Current
 #endif
 
+#if CYTHON_COMPILING_IN_CPYTHON || defined(_PyDict_NewPresized)
+#define __Pyx_PyDict_NewPresized(n)  _PyDict_NewPresized(n)
+#else
+#define __Pyx_PyDict_NewPresized(n)  PyDict_New()
+#endif
+
 #if PY_MAJOR_VERSION >= 3 || CYTHON_FUTURE_DIVISION
   #define __Pyx_PyNumber_Divide(x,y)         PyNumber_TrueDivide(x,y)
   #define __Pyx_PyNumber_InPlaceDivide(x,y)  PyNumber_InPlaceTrueDivide(x,y)

Cython/Utility/Printing.c

@@ -83,7 +83,7 @@ static int __Pyx_Print(PyObject* stream, PyObject *arg_tuple, int newline) {
             return -1;
     }
     if (stream) {
-        kwargs = PyDict_New();
+        kwargs = __Pyx_PyDict_NewPresized(2);
         if (unlikely(!kwargs))
             return -1;
         if (unlikely(PyDict_SetItem(kwargs, PYIDENT("file"), stream) < 0))
@@ -100,7 +100,7 @@ static int __Pyx_Print(PyObject* stream, PyObject *arg_tuple, int newline) {
         }
     } else if (!newline) {
         if (unlikely(!$print_function_kwargs)) {
-            $print_function_kwargs = PyDict_New();
+            $print_function_kwargs = __Pyx_PyDict_NewPresized(1);
             if (unlikely(!$print_function_kwargs))
                 return -1;
             end_string = PyUnicode_FromStringAndSize(" ", 1);