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| author | Raymond Hettinger <python@rcn.com> | 2007-12-18 21:24:09 (GMT) |
|---|---|---|
| committer | Raymond Hettinger <python@rcn.com> | 2007-12-18 21:24:09 (GMT) |
| commit | fd7ed407d79b797e20d0a6fe69e18f9ba9354979 (patch) | |
| tree | 3dc9abccf69e49db5c98aa0805dcbaab50fc90c3 /Python | |
| parent | 3c887b2802e1b44b7e33cd14329541d0d22769d7 (diff) | |
| download | cpython-fd7ed407d79b797e20d0a6fe69e18f9ba9354979.zip cpython-fd7ed407d79b797e20d0a6fe69e18f9ba9354979.tar.gz cpython-fd7ed407d79b797e20d0a6fe69e18f9ba9354979.tar.bz2 | |
Give meaning to the oparg for BUILD_MAP: estimated size of the dictionary.
Allows dictionaries to be pre-sized (upto 255 elements) saving time lost
to re-sizes with their attendant mallocs and re-insertions.
Has zero effect on small dictionaries (5 elements or fewer), a slight
benefit for dicts upto 22 elements (because they had to resize once
anyway), and more benefit for dicts upto 255 elements (saving multiple
resizes during the build-up and reducing the number of collisions on
the first insertions). Beyond 255 elements, there is no addional benefit.
Diffstat (limited to 'Python')
| -rw-r--r-- | Python/ceval.c | 2 | ||||
| -rw-r--r-- | Python/compile.c | 6 |
2 files changed, 3 insertions, 5 deletions
diff --git a/Python/ceval.c b/Python/ceval.c index 1af998d..b6501b3 100644 --- a/Python/ceval.c +++ b/Python/ceval.c @@ -1997,7 +1997,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag) break; case BUILD_MAP: - x = PyDict_New(); + x = _PyDict_NewPresized((Py_ssize_t)oparg); PUSH(x); if (x != NULL) continue; break; diff --git a/Python/compile.c b/Python/compile.c index 3b0c53f..36ad8a4 100644 --- a/Python/compile.c +++ b/Python/compile.c @@ -2922,11 +2922,9 @@ compiler_visit_expr(struct compiler *c, expr_ty e) case IfExp_kind: return compiler_ifexp(c, e); case Dict_kind: - /* XXX get rid of arg? */ - ADDOP_I(c, BUILD_MAP, 0); n = asdl_seq_LEN(e->v.Dict.values); - /* We must arrange things just right for STORE_SUBSCR. - It wants the stack to look like (value) (dict) (key) */ + ADDOP_I(c, BUILD_MAP, (n>255 ? 255 : n)); + n = asdl_seq_LEN(e->v.Dict.values); for (i = 0; i < n; i++) { VISIT(c, expr, (expr_ty)asdl_seq_GET(e->v.Dict.values, i)); |