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Implement PEP 412: Key-sharing dictionaries (closes #13903)

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Patch from Mark Shannon.
This commit is contained in:
Benjamin Peterson 2012-04-23 11:24:50 -04:00
parent 80d07f8251
commit 7d95e40721
12 changed files with 1353 additions and 904 deletions
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84
Include/dictobject.h
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@ -13,78 +13,20 @@ extern "C" {
tuning dictionaries, and several ideas for possible optimizations.
*/
/*
There are three kinds of slots in the table:
1. Unused. me_key == me_value == NULL
Does not hold an active (key, value) pair now and never did. Unused can
transition to Active upon key insertion. This is the only case in which
me_key is NULL, and is each slot's initial state.
2. Active. me_key != NULL and me_key != dummy and me_value != NULL
Holds an active (key, value) pair. Active can transition to Dummy upon
key deletion. This is the only case in which me_value != NULL.
3. Dummy. me_key == dummy and me_value == NULL
Previously held an active (key, value) pair, but that was deleted and an
active pair has not yet overwritten the slot. Dummy can transition to
Active upon key insertion. Dummy slots cannot be made Unused again
(cannot have me_key set to NULL), else the probe sequence in case of
collision would have no way to know they were once active.
Note: .popitem() abuses the me_hash field of an Unused or Dummy slot to
hold a search finger. The me_hash field of Unused or Dummy slots has no
meaning otherwise.
*/
/* PyDict_MINSIZE is the minimum size of a dictionary. This many slots are
* allocated directly in the dict object (in the ma_smalltable member).
* It must be a power of 2, and at least 4. 8 allows dicts with no more
* than 5 active entries to live in ma_smalltable (and so avoid an
* additional malloc); instrumentation suggested this suffices for the
* majority of dicts (consisting mostly of usually-small instance dicts and
* usually-small dicts created to pass keyword arguments).
*/
#ifndef Py_LIMITED_API
#define PyDict_MINSIZE 8
typedef struct _dictkeysobject PyDictKeysObject;
/* The ma_values pointer is NULL for a combined table
* or points to an array of PyObject* for a split table
*/
typedef struct {
/* Cached hash code of me_key. */
Py_hash_t me_hash;
PyObject *me_key;
PyObject *me_value;
} PyDictEntry;
/*
To ensure the lookup algorithm terminates, there must be at least one Unused
slot (NULL key) in the table.
The value ma_fill is the number of non-NULL keys (sum of Active and Dummy);
ma_used is the number of non-NULL, non-dummy keys (== the number of non-NULL
values == the number of Active items).
To avoid slowing down lookups on a near-full table, we resize the table when
it's two-thirds full.
*/
typedef struct _dictobject PyDictObject;
struct _dictobject {
PyObject_HEAD
Py_ssize_t ma_fill; /* # Active + # Dummy */
Py_ssize_t ma_used; /* # Active */
Py_ssize_t ma_used;
PyDictKeysObject *ma_keys;
PyObject **ma_values;
} PyDictObject;
/* The table contains ma_mask + 1 slots, and that's a power of 2.
* We store the mask instead of the size because the mask is more
* frequently needed.
*/
Py_ssize_t ma_mask;
/* ma_table points to ma_smalltable for small tables, else to
* additional malloc'ed memory. ma_table is never NULL! This rule
* saves repeated runtime null-tests in the workhorse getitem and
* setitem calls.
*/
PyDictEntry *ma_table;
PyDictEntry *(*ma_lookup)(PyDictObject *mp, PyObject *key, Py_hash_t hash);
PyDictEntry ma_smalltable[PyDict_MINSIZE];
};
#endif /* Py_LIMITED_API */
PyAPI_DATA(PyTypeObject) PyDict_Type;
@ -117,6 +59,8 @@ PyAPI_FUNC(void) PyDict_Clear(PyObject *mp);
PyAPI_FUNC(int) PyDict_Next(
PyObject *mp, Py_ssize_t *pos, PyObject **key, PyObject **value);
#ifndef Py_LIMITED_API
PyDictKeysObject *_PyDict_NewKeysForClass(void);
PyAPI_FUNC(PyObject *) PyObject_GenericGetDict(PyObject *, void *);
PyAPI_FUNC(int) _PyDict_Next(
PyObject *mp, Py_ssize_t *pos, PyObject **key, PyObject **value, Py_hash_t *hash);
#endif
@ -131,6 +75,7 @@ PyAPI_FUNC(int) _PyDict_Contains(PyObject *mp, PyObject *key, Py_hash_t hash);
PyAPI_FUNC(PyObject *) _PyDict_NewPresized(Py_ssize_t minused);
PyAPI_FUNC(void) _PyDict_MaybeUntrack(PyObject *mp);
PyAPI_FUNC(int) _PyDict_HasOnlyStringKeys(PyObject *mp);
#define _PyDict_HasSplitTable(d) ((d)->ma_values != NULL)
PyAPI_FUNC(int) PyDict_ClearFreeList(void);
#endif
@ -162,6 +107,11 @@ PyAPI_FUNC(int) PyDict_SetItemString(PyObject *dp, const char *key, PyObject *it
PyAPI_FUNC(int) _PyDict_SetItemId(PyObject *dp, struct _Py_Identifier *key, PyObject *item);
PyAPI_FUNC(int) PyDict_DelItemString(PyObject *dp, const char *key);
#ifndef Py_LIMITED_API
int _PyObjectDict_SetItem(PyTypeObject *tp, PyObject **dictptr, PyObject *name, PyObject *value);
PyObject *_PyDict_LoadGlobal(PyDictObject *, PyDictObject *, PyObject *);
#endif
#ifdef __cplusplus
}
#endif