/Modules/_randommodule.c
http://unladen-swallow.googlecode.com/ · C · 580 lines · 391 code · 60 blank · 129 comment · 89 complexity · f79f21b2c33a3f4dda811a0cc29d6f17 MD5 · raw file
- /* Random objects */
- /* ------------------------------------------------------------------
- The code in this module was based on a download from:
- http://www.math.keio.ac.jp/~matumoto/MT2002/emt19937ar.html
- It was modified in 2002 by Raymond Hettinger as follows:
- * the principal computational lines untouched except for tabbing.
- * renamed genrand_res53() to random_random() and wrapped
- in python calling/return code.
- * genrand_int32() and the helper functions, init_genrand()
- and init_by_array(), were declared static, wrapped in
- Python calling/return code. also, their global data
- references were replaced with structure references.
- * unused functions from the original were deleted.
- new, original C python code was added to implement the
- Random() interface.
- The following are the verbatim comments from the original code:
- A C-program for MT19937, with initialization improved 2002/1/26.
- Coded by Takuji Nishimura and Makoto Matsumoto.
- Before using, initialize the state by using init_genrand(seed)
- or init_by_array(init_key, key_length).
- Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
- All rights reserved.
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
- 1. Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- 2. Redistributions in binary form must reproduce the above copyright
- notice, this list of conditions and the following disclaimer in the
- documentation and/or other materials provided with the distribution.
- 3. The names of its contributors may not be used to endorse or promote
- products derived from this software without specific prior written
- permission.
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
- CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
- LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- Any feedback is very welcome.
- http://www.math.keio.ac.jp/matumoto/emt.html
- email: matumoto@math.keio.ac.jp
- */
- /* ---------------------------------------------------------------*/
- #include "Python.h"
- #include <time.h> /* for seeding to current time */
- /* Period parameters -- These are all magic. Don't change. */
- #define N 624
- #define M 397
- #define MATRIX_A 0x9908b0dfUL /* constant vector a */
- #define UPPER_MASK 0x80000000UL /* most significant w-r bits */
- #define LOWER_MASK 0x7fffffffUL /* least significant r bits */
- typedef struct {
- PyObject_HEAD
- unsigned long state[N];
- int index;
- } RandomObject;
- static PyTypeObject Random_Type;
- #define RandomObject_Check(v) (Py_TYPE(v) == &Random_Type)
- /* Random methods */
- /* generates a random number on [0,0xffffffff]-interval */
- static unsigned long
- genrand_int32(RandomObject *self)
- {
- unsigned long y;
- static unsigned long mag01[2]={0x0UL, MATRIX_A};
- /* mag01[x] = x * MATRIX_A for x=0,1 */
- unsigned long *mt;
- mt = self->state;
- if (self->index >= N) { /* generate N words at one time */
- int kk;
- for (kk=0;kk<N-M;kk++) {
- y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
- mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
- }
- for (;kk<N-1;kk++) {
- y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
- mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
- }
- y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
- mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];
- self->index = 0;
- }
- y = mt[self->index++];
- y ^= (y >> 11);
- y ^= (y << 7) & 0x9d2c5680UL;
- y ^= (y << 15) & 0xefc60000UL;
- y ^= (y >> 18);
- return y;
- }
- /* random_random is the function named genrand_res53 in the original code;
- * generates a random number on [0,1) with 53-bit resolution; note that
- * 9007199254740992 == 2**53; I assume they're spelling "/2**53" as
- * multiply-by-reciprocal in the (likely vain) hope that the compiler will
- * optimize the division away at compile-time. 67108864 is 2**26. In
- * effect, a contains 27 random bits shifted left 26, and b fills in the
- * lower 26 bits of the 53-bit numerator.
- * The orginal code credited Isaku Wada for this algorithm, 2002/01/09.
- */
- static PyObject *
- random_random(RandomObject *self)
- {
- unsigned long a=genrand_int32(self)>>5, b=genrand_int32(self)>>6;
- return PyFloat_FromDouble((a*67108864.0+b)*(1.0/9007199254740992.0));
- }
- /* initializes mt[N] with a seed */
- static void
- init_genrand(RandomObject *self, unsigned long s)
- {
- int mti;
- unsigned long *mt;
- mt = self->state;
- mt[0]= s & 0xffffffffUL;
- for (mti=1; mti<N; mti++) {
- mt[mti] =
- (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);
- /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
- /* In the previous versions, MSBs of the seed affect */
- /* only MSBs of the array mt[]. */
- /* 2002/01/09 modified by Makoto Matsumoto */
- mt[mti] &= 0xffffffffUL;
- /* for >32 bit machines */
- }
- self->index = mti;
- return;
- }
- /* initialize by an array with array-length */
- /* init_key is the array for initializing keys */
- /* key_length is its length */
- static PyObject *
- init_by_array(RandomObject *self, unsigned long init_key[], unsigned long key_length)
- {
- unsigned int i, j, k; /* was signed in the original code. RDH 12/16/2002 */
- unsigned long *mt;
- mt = self->state;
- init_genrand(self, 19650218UL);
- i=1; j=0;
- k = (N>key_length ? N : key_length);
- for (; k; k--) {
- mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL))
- + init_key[j] + j; /* non linear */
- mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
- i++; j++;
- if (i>=N) { mt[0] = mt[N-1]; i=1; }
- if (j>=key_length) j=0;
- }
- for (k=N-1; k; k--) {
- mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL))
- - i; /* non linear */
- mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
- i++;
- if (i>=N) { mt[0] = mt[N-1]; i=1; }
- }
- mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
- Py_INCREF(Py_None);
- return Py_None;
- }
- /*
- * The rest is Python-specific code, neither part of, nor derived from, the
- * Twister download.
- */
- static PyObject *
- random_seed(RandomObject *self, PyObject *args)
- {
- PyObject *result = NULL; /* guilty until proved innocent */
- PyObject *masklower = NULL;
- PyObject *thirtytwo = NULL;
- PyObject *n = NULL;
- unsigned long *key = NULL;
- unsigned long keymax; /* # of allocated slots in key */
- unsigned long keyused; /* # of used slots in key */
- int err;
- PyObject *arg = NULL;
- if (!PyArg_UnpackTuple(args, "seed", 0, 1, &arg))
- return NULL;
- if (arg == NULL || arg == Py_None) {
- time_t now;
- time(&now);
- init_genrand(self, (unsigned long)now);
- Py_INCREF(Py_None);
- return Py_None;
- }
- /* If the arg is an int or long, use its absolute value; else use
- * the absolute value of its hash code.
- */
- if (PyInt_Check(arg) || PyLong_Check(arg))
- n = PyNumber_Absolute(arg);
- else {
- long hash = PyObject_Hash(arg);
- if (hash == -1)
- goto Done;
- n = PyLong_FromUnsignedLong((unsigned long)hash);
- }
- if (n == NULL)
- goto Done;
- /* Now split n into 32-bit chunks, from the right. Each piece is
- * stored into key, which has a capacity of keymax chunks, of which
- * keyused are filled. Alas, the repeated shifting makes this a
- * quadratic-time algorithm; we'd really like to use
- * _PyLong_AsByteArray here, but then we'd have to break into the
- * long representation to figure out how big an array was needed
- * in advance.
- */
- keymax = 8; /* arbitrary; grows later if needed */
- keyused = 0;
- key = (unsigned long *)PyMem_Malloc(keymax * sizeof(*key));
- if (key == NULL)
- goto Done;
- masklower = PyLong_FromUnsignedLong(0xffffffffU);
- if (masklower == NULL)
- goto Done;
- thirtytwo = PyInt_FromLong(32L);
- if (thirtytwo == NULL)
- goto Done;
- while ((err=PyObject_IsTrue(n))) {
- PyObject *newn;
- PyObject *pychunk;
- unsigned long chunk;
- if (err == -1)
- goto Done;
- pychunk = PyNumber_And(n, masklower);
- if (pychunk == NULL)
- goto Done;
- chunk = PyLong_AsUnsignedLong(pychunk);
- Py_DECREF(pychunk);
- if (chunk == (unsigned long)-1 && PyErr_Occurred())
- goto Done;
- newn = PyNumber_Rshift(n, thirtytwo);
- if (newn == NULL)
- goto Done;
- Py_DECREF(n);
- n = newn;
- if (keyused >= keymax) {
- unsigned long bigger = keymax << 1;
- if ((bigger >> 1) != keymax) {
- PyErr_NoMemory();
- goto Done;
- }
- key = (unsigned long *)PyMem_Realloc(key,
- bigger * sizeof(*key));
- if (key == NULL)
- goto Done;
- keymax = bigger;
- }
- assert(keyused < keymax);
- key[keyused++] = chunk;
- }
- if (keyused == 0)
- key[keyused++] = 0UL;
- result = init_by_array(self, key, keyused);
- Done:
- Py_XDECREF(masklower);
- Py_XDECREF(thirtytwo);
- Py_XDECREF(n);
- PyMem_Free(key);
- return result;
- }
- static PyObject *
- random_getstate(RandomObject *self)
- {
- PyObject *state;
- PyObject *element;
- int i;
- state = PyTuple_New(N+1);
- if (state == NULL)
- return NULL;
- for (i=0; i<N ; i++) {
- element = PyLong_FromUnsignedLong(self->state[i]);
- if (element == NULL)
- goto Fail;
- PyTuple_SET_ITEM(state, i, element);
- }
- element = PyLong_FromLong((long)(self->index));
- if (element == NULL)
- goto Fail;
- PyTuple_SET_ITEM(state, i, element);
- return state;
- Fail:
- Py_DECREF(state);
- return NULL;
- }
- static PyObject *
- random_setstate(RandomObject *self, PyObject *state)
- {
- int i;
- unsigned long element;
- long index;
- if (!PyTuple_Check(state)) {
- PyErr_SetString(PyExc_TypeError,
- "state vector must be a tuple");
- return NULL;
- }
- if (PyTuple_Size(state) != N+1) {
- PyErr_SetString(PyExc_ValueError,
- "state vector is the wrong size");
- return NULL;
- }
- for (i=0; i<N ; i++) {
- element = PyLong_AsUnsignedLong(PyTuple_GET_ITEM(state, i));
- if (element == (unsigned long)-1 && PyErr_Occurred())
- return NULL;
- self->state[i] = element & 0xffffffffUL; /* Make sure we get sane state */
- }
- index = PyLong_AsLong(PyTuple_GET_ITEM(state, i));
- if (index == -1 && PyErr_Occurred())
- return NULL;
- self->index = (int)index;
- Py_INCREF(Py_None);
- return Py_None;
- }
- /*
- Jumpahead should be a fast way advance the generator n-steps ahead, but
- lacking a formula for that, the next best is to use n and the existing
- state to create a new state far away from the original.
- The generator uses constant spaced additive feedback, so shuffling the
- state elements ought to produce a state which would not be encountered
- (in the near term) by calls to random(). Shuffling is normally
- implemented by swapping the ith element with another element ranging
- from 0 to i inclusive. That allows the element to have the possibility
- of not being moved. Since the goal is to produce a new, different
- state, the swap element is ranged from 0 to i-1 inclusive. This assures
- that each element gets moved at least once.
- To make sure that consecutive calls to jumpahead(n) produce different
- states (even in the rare case of involutory shuffles), i+1 is added to
- each element at position i. Successive calls are then guaranteed to
- have changing (growing) values as well as shuffled positions.
- Finally, the self->index value is set to N so that the generator itself
- kicks in on the next call to random(). This assures that all results
- have been through the generator and do not just reflect alterations to
- the underlying state.
- */
- static PyObject *
- random_jumpahead(RandomObject *self, PyObject *n)
- {
- long i, j;
- PyObject *iobj;
- PyObject *remobj;
- unsigned long *mt, tmp;
- if (!PyInt_Check(n) && !PyLong_Check(n)) {
- PyErr_Format(PyExc_TypeError, "jumpahead requires an "
- "integer, not '%s'",
- Py_TYPE(n)->tp_name);
- return NULL;
- }
- mt = self->state;
- for (i = N-1; i > 1; i--) {
- iobj = PyInt_FromLong(i);
- if (iobj == NULL)
- return NULL;
- remobj = PyNumber_Remainder(n, iobj);
- Py_DECREF(iobj);
- if (remobj == NULL)
- return NULL;
- j = PyInt_AsLong(remobj);
- Py_DECREF(remobj);
- if (j == -1L && PyErr_Occurred())
- return NULL;
- tmp = mt[i];
- mt[i] = mt[j];
- mt[j] = tmp;
- }
- for (i = 0; i < N; i++)
- mt[i] += i+1;
- self->index = N;
- Py_INCREF(Py_None);
- return Py_None;
- }
- static PyObject *
- random_getrandbits(RandomObject *self, PyObject *args)
- {
- int k, i, bytes;
- unsigned long r;
- unsigned char *bytearray;
- PyObject *result;
- if (!PyArg_ParseTuple(args, "i:getrandbits", &k))
- return NULL;
- if (k <= 0) {
- PyErr_SetString(PyExc_ValueError,
- "number of bits must be greater than zero");
- return NULL;
- }
- bytes = ((k - 1) / 32 + 1) * 4;
- bytearray = (unsigned char *)PyMem_Malloc(bytes);
- if (bytearray == NULL) {
- PyErr_NoMemory();
- return NULL;
- }
- /* Fill-out whole words, byte-by-byte to avoid endianness issues */
- for (i=0 ; i<bytes ; i+=4, k-=32) {
- r = genrand_int32(self);
- if (k < 32)
- r >>= (32 - k);
- bytearray[i+0] = (unsigned char)r;
- bytearray[i+1] = (unsigned char)(r >> 8);
- bytearray[i+2] = (unsigned char)(r >> 16);
- bytearray[i+3] = (unsigned char)(r >> 24);
- }
- /* little endian order to match bytearray assignment order */
- result = _PyLong_FromByteArray(bytearray, bytes, 1, 0);
- PyMem_Free(bytearray);
- return result;
- }
- static PyObject *
- random_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
- {
- RandomObject *self;
- PyObject *tmp;
- if (type == &Random_Type && !_PyArg_NoKeywords("Random()", kwds))
- return NULL;
- self = (RandomObject *)type->tp_alloc(type, 0);
- if (self == NULL)
- return NULL;
- tmp = random_seed(self, args);
- if (tmp == NULL) {
- Py_DECREF(self);
- return NULL;
- }
- Py_DECREF(tmp);
- return (PyObject *)self;
- }
- static PyMethodDef random_methods[] = {
- {"random", (PyCFunction)random_random, METH_NOARGS,
- PyDoc_STR("random() -> x in the interval [0, 1).")},
- {"seed", (PyCFunction)random_seed, METH_VARARGS,
- PyDoc_STR("seed([n]) -> None. Defaults to current time.")},
- {"getstate", (PyCFunction)random_getstate, METH_NOARGS,
- PyDoc_STR("getstate() -> tuple containing the current state.")},
- {"setstate", (PyCFunction)random_setstate, METH_O,
- PyDoc_STR("setstate(state) -> None. Restores generator state.")},
- {"jumpahead", (PyCFunction)random_jumpahead, METH_O,
- PyDoc_STR("jumpahead(int) -> None. Create new state from "
- "existing state and integer.")},
- {"getrandbits", (PyCFunction)random_getrandbits, METH_VARARGS,
- PyDoc_STR("getrandbits(k) -> x. Generates a long int with "
- "k random bits.")},
- {NULL, NULL} /* sentinel */
- };
- PyDoc_STRVAR(random_doc,
- "Random() -> create a random number generator with its own internal state.");
- static PyTypeObject Random_Type = {
- PyVarObject_HEAD_INIT(NULL, 0)
- "_random.Random", /*tp_name*/
- sizeof(RandomObject), /*tp_basicsize*/
- 0, /*tp_itemsize*/
- /* methods */
- 0, /*tp_dealloc*/
- 0, /*tp_print*/
- 0, /*tp_getattr*/
- 0, /*tp_setattr*/
- 0, /*tp_compare*/
- 0, /*tp_repr*/
- 0, /*tp_as_number*/
- 0, /*tp_as_sequence*/
- 0, /*tp_as_mapping*/
- 0, /*tp_hash*/
- 0, /*tp_call*/
- 0, /*tp_str*/
- PyObject_GenericGetAttr, /*tp_getattro*/
- 0, /*tp_setattro*/
- 0, /*tp_as_buffer*/
- Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
- random_doc, /*tp_doc*/
- 0, /*tp_traverse*/
- 0, /*tp_clear*/
- 0, /*tp_richcompare*/
- 0, /*tp_weaklistoffset*/
- 0, /*tp_iter*/
- 0, /*tp_iternext*/
- random_methods, /*tp_methods*/
- 0, /*tp_members*/
- 0, /*tp_getset*/
- 0, /*tp_base*/
- 0, /*tp_dict*/
- 0, /*tp_descr_get*/
- 0, /*tp_descr_set*/
- 0, /*tp_dictoffset*/
- 0, /*tp_init*/
- 0, /*tp_alloc*/
- random_new, /*tp_new*/
- _PyObject_Del, /*tp_free*/
- 0, /*tp_is_gc*/
- };
- PyDoc_STRVAR(module_doc,
- "Module implements the Mersenne Twister random number generator.");
- PyMODINIT_FUNC
- init_random(void)
- {
- PyObject *m;
- if (PyType_Ready(&Random_Type) < 0)
- return;
- m = Py_InitModule3("_random", NULL, module_doc);
- if (m == NULL)
- return;
- Py_INCREF(&Random_Type);
- PyModule_AddObject(m, "Random", (PyObject *)&Random_Type);
- }