Charles G Waldman:

Follow a suggestion in an /*XXX*/ comment [in com_add()] to speed up
compilation by using supplemental dictionaries to keep track of names
and constants, eliminating quadratic behavior.  With this patch in
place, the time to import a 5000-line file with lots of constants [at
the global level] is reduced from 20 seconds to under 3 on my system.

diff --git a/Python/compile.c b/Python/compile.c
index 453aae35e9c225f01819a5a7bdcaacc580966fd8..6d330cf5380fa21ac5e53b0e02a6b938d7ff5645 100644 (file)
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -301,7 +301,9 @@ PyCode_New(argcount, nlocals, stacksize, flags,
 struct compiling {
        PyObject *c_code;               /* string */
        PyObject *c_consts;     /* list of objects */
+       PyObject *c_const_dict; /* inverse of c_consts */
        PyObject *c_names;      /* list of strings (names) */
+       PyObject *c_name_dict;  /* inverse of c_names */
        PyObject *c_globals;    /* dictionary (value=None) */
        PyObject *c_locals;     /* dictionary (value=localID) */
        PyObject *c_varnames;   /* list (inverse of c_locals) */
@@ -403,7 +405,7 @@ static void com_addint Py_PROTO((struct compiling *, int));
 static void com_addoparg Py_PROTO((struct compiling *, int, int));
 static void com_addfwref Py_PROTO((struct compiling *, int, int *));
 static void com_backpatch Py_PROTO((struct compiling *, int));
-static int com_add Py_PROTO((struct compiling *, PyObject *, PyObject *));
+static int com_add Py_PROTO((struct compiling *, PyObject *, PyObject *, PyObject *));
 static int com_addconst Py_PROTO((struct compiling *, PyObject *));
 static int com_addname Py_PROTO((struct compiling *, PyObject *));
 static void com_addopname Py_PROTO((struct compiling *, int, node *));
@@ -421,22 +423,27 @@ com_init(c, filename)
        struct compiling *c;
        char *filename;
 {
+       memset((void *)c, '\0', sizeof(struct compiling));
        if ((c->c_code = PyString_FromStringAndSize((char *)NULL,
                                                    1000)) == NULL)
-               goto fail_3;
+               goto fail;
        if ((c->c_consts = PyList_New(0)) == NULL)
-               goto fail_2;
+               goto fail;
+       if ((c->c_const_dict = PyDict_New()) == NULL)
+               goto fail;
        if ((c->c_names = PyList_New(0)) == NULL)
-               goto fail_1;
+               goto fail;
+       if ((c->c_name_dict = PyDict_New()) == NULL)
+               goto fail;
        if ((c->c_globals = PyDict_New()) == NULL)
-               goto fail_0;
+               goto fail;
        if ((c->c_locals = PyDict_New()) == NULL)
-               goto fail_00;
+               goto fail;
        if ((c->c_varnames = PyList_New(0)) == NULL)
-               goto fail_000;
+               goto fail;
        if ((c->c_lnotab = PyString_FromStringAndSize((char *)NULL,
                                                      1000)) == NULL)
-               goto fail_0000;
+               goto fail;
        c->c_nlocals = 0;
        c->c_argcount = 0;
        c->c_flags = 0;
@@ -458,19 +465,8 @@ com_init(c, filename)
        c-> c_lnotab_next = 0;
        return 1;
        
-  fail_0000:
-       Py_DECREF(c->c_varnames);
-  fail_000:
-       Py_DECREF(c->c_locals);
-  fail_00:
-       Py_DECREF(c->c_globals);
-  fail_0:
-       Py_DECREF(c->c_names);
-  fail_1:
-       Py_DECREF(c->c_consts);
-  fail_2:
-       Py_DECREF(c->c_code);
-  fail_3:
+  fail:
+       com_free(c);
        return 0;
 }
 
@@ -480,7 +476,9 @@ com_free(c)
 {
        Py_XDECREF(c->c_code);
        Py_XDECREF(c->c_consts);
+       Py_XDECREF(c->c_const_dict);
        Py_XDECREF(c->c_names);
+       Py_XDECREF(c->c_name_dict);
        Py_XDECREF(c->c_globals);
        Py_XDECREF(c->c_locals);
        Py_XDECREF(c->c_varnames);
@@ -665,24 +663,39 @@ com_backpatch(c, anchor)
 /* Handle literals and names uniformly */
 
 static int
-com_add(c, list, v)
+com_add(c, list, dict, v)
        struct compiling *c;
        PyObject *list;
+       PyObject *dict;
        PyObject *v;
 {
-       int n = PyList_Size(list);
-       int i;
-       /* XXX This is quadratic in the number of names per compilation unit.
-          XXX Should use a dictionary. */
-       for (i = n; --i >= 0; ) {
-               PyObject *w = PyList_GetItem(list, i);
-               if (v->ob_type == w->ob_type && PyObject_Compare(v, w) == 0)
-                       return i;
-       }
-       /* Check for error from PyObject_Compare */
-       if (PyErr_Occurred() || PyList_Append(list, v) != 0)
-               c->c_errors++;
+       PyObject *w, *t, *np=NULL;
+       long n;
+
+       t = Py_BuildValue("(OO)", v, v->ob_type);
+       if (t == NULL)
+           goto fail;
+       w = PyDict_GetItem(dict, t);
+       if (w != NULL) {
+               n = PyInt_AsLong(w);
+       } else {
+               n = PyList_Size(list);
+               np = PyInt_FromLong(n);
+               if (np == NULL)
+                   goto fail;
+               if (PyList_Append(list, v) != 0)
+                   goto fail;
+               if (PyDict_SetItem(dict, t, np) != 0)
+                   goto fail;
+               Py_DECREF(np);
+       }
+       Py_DECREF(t);
        return n;
+  fail:
+       Py_XDECREF(np);
+       Py_XDECREF(t);
+       c->c_errors++;
+       return 0;
 }
 
 static int
@@ -690,7 +703,7 @@ com_addconst(c, v)
        struct compiling *c;
        PyObject *v;
 {
-       return com_add(c, c->c_consts, v);
+       return com_add(c, c->c_consts, c->c_const_dict, v);
 }
 
 static int
@@ -698,7 +711,7 @@ com_addname(c, v)
        struct compiling *c;
        PyObject *v;
 {
-       return com_add(c, c->c_names, v);
+       return com_add(c, c->c_names, c->c_name_dict, v);
 }
 
 #ifdef PRIVATE_NAME_MANGLING