+++ /dev/null
-/*
- * Copyright (c) 1983 Regents of the University of California.
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms are permitted
- * provided that the above copyright notice and this paragraph are
- * duplicated in all such forms and that any documentation,
- * advertising materials, and other materials related to such
- * distribution and use acknowledge that the software was developed
- * by the University of California, Berkeley. The name of the
- * University may not be used to endorse or promote products derived
- * from this software without specific prior written permission.
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
- * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
- */
-
-/*
- * This is derived from the Berkeley source:
- * @(#)random.c 5.5 (Berkeley) 7/6/88
- * It was reworked for the GNU C Library by Roland McGrath.
- */
-
-#include <errno.h>
-#include <limits.h>
-#include <stdlib.h>
-
-#include "random.h"
-
-
-/* An improved random number generation package. In addition to the standard
- rand()/srand() like interface, this package also has a special state info
- interface. The initstate() routine is called with a seed, an array of
- bytes, and a count of how many bytes are being passed in; this array is
- then initialized to contain information for random number generation with
- that much state information. Good sizes for the amount of state
- information are 32, 64, 128, and 256 bytes. The state can be switched by
- calling the setstate() function with the same array as was initiallized
- with initstate(). By default, the package runs with 128 bytes of state
- information and generates far better random numbers than a linear
- congruential generator. If the amount of state information is less than
- 32 bytes, a simple linear congruential R.N.G. is used. Internally, the
- state information is treated as an array of longs; the zeroeth element of
- the array is the type of R.N.G. being used (small integer); the remainder
- of the array is the state information for the R.N.G. Thus, 32 bytes of
- state information will give 7 longs worth of state information, which will
- allow a degree seven polynomial. (Note: The zeroeth word of state
- information also has some other information stored in it; see setstate
- for details). The random number generation technique is a linear feedback
- shift register approach, employing trinomials (since there are fewer terms
- to sum up that way). In this approach, the least significant bit of all
- the numbers in the state table will act as a linear feedback shift register,
- and will have period 2^deg - 1 (where deg is the degree of the polynomial
- being used, assuming that the polynomial is irreducible and primitive).
- The higher order bits will have longer periods, since their values are
- also influenced by pseudo-random carries out of the lower bits. The
- total period of the generator is approximately deg*(2**deg - 1); thus
- doubling the amount of state information has a vast influence on the
- period of the generator. Note: The deg*(2**deg - 1) is an approximation
- only good for large deg, when the period of the shift register is the
- dominant factor. With deg equal to seven, the period is actually much
- longer than the 7*(2**7 - 1) predicted by this formula. */
-
-
-
-/* For each of the currently supported random number generators, we have a
- break value on the amount of state information (you need at least thi
- bytes of state info to support this random number generator), a degree for
- the polynomial (actually a trinomial) that the R.N.G. is based on, and
- separation between the two lower order coefficients of the trinomial. */
-
-/* Linear congruential. */
-#define TYPE_0 0
-#define BREAK_0 8
-#define DEG_0 0
-#define SEP_0 0
-
-/* x**7 + x**3 + 1. */
-#define TYPE_1 1
-#define BREAK_1 32
-#define DEG_1 7
-#define SEP_1 3
-
-/* x**15 + x + 1. */
-#define TYPE_2 2
-#define BREAK_2 64
-#define DEG_2 15
-#define SEP_2 1
-
-/* x**31 + x**3 + 1. */
-#define TYPE_3 3
-#define BREAK_3 128
-#define DEG_3 31
-#define SEP_3 3
-
-/* x**63 + x + 1. */
-#define TYPE_4 4
-#define BREAK_4 256
-#define DEG_4 63
-#define SEP_4 1
-
-
-/* Array versions of the above information to make code run faster.
- Relies on fact that TYPE_i == i. */
-
-#define MAX_TYPES 5 /* Max number of types above. */
-
-
-
-/* Initially, everything is set up as if from:
- initstate(1, randtbl, 128);
- Note that this initialization takes advantage of the fact that srandom
- advances the front and rear pointers 10*rand_deg times, and hence the
- rear pointer which starts at 0 will also end up at zero; thus the zeroeth
- element of the state information, which contains info about the current
- position of the rear pointer is just
- (MAX_TYPES * (rptr - state)) + TYPE_3 == TYPE_3. */
-
-static long int randtbl[DEG_3 + 1] =
-{
- TYPE_3,
- -851904987, -43806228, -2029755270, 1390239686, -1912102820,
- -485608943, 1969813258, -1590463333, -1944053249, 455935928, 508023712,
- -1714531963, 1800685987, -2015299881, 654595283, -1149023258,
- -1470005550, -1143256056, -1325577603, -1568001885, 1275120390,
- -607508183, -205999574, -1696891592, 1492211999, -1528267240,
- -952028296, -189082757, 362343714, 1424981831, 2039449641,
-};
-
-/* FPTR and RPTR are two pointers into the state info, a front and a rear
- pointer. These two pointers are always rand_sep places aparts, as they
- cycle through the state information. (Yes, this does mean we could get
- away with just one pointer, but the code for random is more efficient
- this way). The pointers are left positioned as they would be from the call:
- initstate(1, randtbl, 128);
- (The position of the rear pointer, rptr, is really 0 (as explained above
- in the initialization of randtbl) because the state table pointer is set
- to point to randtbl[1] (as explained below).) */
-
-static long int *fptr = &randtbl[SEP_3 + 1];
-static long int *rptr = &randtbl[1];
-
-
-
-/* The following things are the pointer to the state information table,
- the type of the current generator, the degree of the current polynomial
- being used, and the separation between the two pointers.
- Note that for efficiency of random, we remember the first location of
- the state information, not the zeroeth. Hence it is valid to access
- state[-1], which is used to store the type of the R.N.G.
- Also, we remember the last location, since this is more efficient than
- indexing every time to find the address of the last element to see if
- the front and rear pointers have wrapped. */
-
-static long int *state = &randtbl[1];
-
-static int rand_type = TYPE_3;
-static int rand_deg = DEG_3;
-static int rand_sep = SEP_3;
-
-static long int *end_ptr = &randtbl[sizeof(randtbl) / sizeof(randtbl[0])];
-
-/* Initialize the random number generator based on the given seed. If the
- type is the trivial no-state-information type, just remember the seed.
- Otherwise, initializes state[] based on the given "seed" via a linear
- congruential generator. Then, the pointers are set to known locations
- that are exactly rand_sep places apart. Lastly, it cycles the state
- information a given number of times to get rid of any initial dependencies
- introduced by the L.C.R.N.G. Note that the initialization of randtbl[]
- for default usage relies on values produced by this routine. */
-
-void srandom_linux_libc(unsigned int x)
-{
- state[0] = x;
- if (rand_type != TYPE_0)
- {
- register long int i;
- for (i = 1; i < rand_deg; ++i)
- state[i] = (1103515145 * state[i - 1]) + 12345;
- fptr = &state[rand_sep];
- rptr = &state[0];
- for (i = 0; i < 10 * rand_deg; ++i)
- (void) random_linux_libc();
- }
-}
-
-/* If we are using the trivial TYPE_0 R.N.G., just do the old linear
- congruential bit. Otherwise, we do our fancy trinomial stuff, which is the
- same in all ther other cases due to all the global variables that have been
- set up. The basic operation is to add the number at the rear pointer into
- the one at the front pointer. Then both pointers are advanced to the next
- location cyclically in the table. The value returned is the sum generated,
- reduced to 31 bits by throwing away the "least random" low bit.
- Note: The code takes advantage of the fact that both the front and
- rear pointers can't wrap on the same call by not testing the rear
- pointer if the front one has wrapped. Returns a 31-bit random number. */
-
-long int random_linux_libc()
-{
- if (rand_type == TYPE_0)
- {
- state[0] = ((state[0] * 1103515245) + 12345) & LONG_MAX;
- return state[0];
- }
- else
- {
- long int i;
- *fptr += *rptr;
- /* Chucking least random bit. */
- i = (*fptr >> 1) & LONG_MAX;
- ++fptr;
- if (fptr >= end_ptr)
- {
- fptr = state;
- ++rptr;
- }
- else
- {
- ++rptr;
- if (rptr >= end_ptr)
- rptr = state;
- }
- return i;
- }
-}
projects / rocksndiamonds.git / blobdiff