如果我们在两者中都提供相同的种子,我需要一个在iOS和
Android中产生相同数字序列的随机数生成器.
我用srand(1000)尝试了rand()函数.但它给出了不同的输出.
然后我尝试了mersenne twister.但这也为同一种子提供了不同的序列.
有谁可以帮我这个.
我正在使用cocos2d-x进行开发.
解决方法
我已经改编了一个在线CRandomMersenne库,我真的很抱歉,我再也找不到那个来源了.但这是我的Mersenne Twister实施：
// Define 32 bit signed and unsigned integers.
// Change these deFinitions,if necessary,to match a particular platform
#if defined(_WIN16) || defined(__MSDOS__) || defined(_MSDOS)
// 16 bit systems use long int for 32 bit integer
typedef long int int32; // 32 bit signed integer
typedef unsigned long int uint32; // 32 bit unsigned integer
#else
// Most other systems use int for 32 bit integer
typedef int int32; // 32 bit signed integer
typedef unsigned int uint32; // 32 bit unsigned integer
#endif
// Define 64 bit signed and unsigned integers,if possible
#if (defined(__WINDOWS__) || defined(_WIN32)) && (defined(_MSC_VER) || defined(__INTEL_COMPILER))
// Microsoft and other compilers under Windows use __int64
typedef __int64 int64; // 64 bit signed integer
typedef unsigned __int64 uint64; // 64 bit unsigned integer
#define INT64_DEFINED // Remember that int64 is defined
#elif defined(__unix__) && (defined(_M_IX86) || defined(_M_X64))
// Gnu and other compilers under Linux etc. use long long
typedef long long int64; // 64 bit signed integer
typedef unsigned long long uint64; // 64 bit unsigned integer
#define INT64_DEFINED // Remember that int64 is defined
#else
// 64 bit integers not defined
// You may include deFinitions for other platforms here
#endif
void EndOfProgram(void); // System-specific exit code (userintf.cpp)
void FatalError(char * ErrorText); // System-specific error reporting (userintf.cpp)
class CRandomMersenne { // Encapsulate random number generator
#if 0
// Define constants for type MT11213A:
#define MERS_N 351
#define MERS_M 175
#define MERS_R 19
#define MERS_U 11
#define MERS_S 7
#define MERS_T 15
#define MERS_L 17
#define MERS_A 0xE4BD75F5
#define MERS_B 0x655E5280
#define MERS_C 0xFFD58000
#else
// or constants for type MT19937:
#define MERS_N 624
#define MERS_M 397
#define MERS_R 31
#define MERS_U 11
#define MERS_S 7
#define MERS_T 15
#define MERS_L 18
#define MERS_A 0x9908B0DF
#define MERS_B 0x9D2C5680
#define MERS_C 0xEFC60000
#endif
public:
CRandomMersenne(uint32 seed) { // Constructor
RandomInit(seed); LastInterval = 0;}
void RandomInit(uint32 seed); // Re-seed
void RandomInitByArray(uint32 seeds[],int length); // Seed by more than 32 bits
int IRandom (int min,int max); // Output random integer
int IRandomX(int min,int max); // Output random integer,exact
double Random(); // Output random float
uint32 BRandom(); // Output random bits
private:
void Init0(uint32 seed); // Basic initialization procedure
uint32 mt[MERS_N]; // State vector
int mti; // Index into mt
uint32 LastInterval; // Last interval length for IRandomX
uint32 RLimit; // Rejection limit used by IRandomX
enum TArch {LITTLE_ENDIAN1,BIG_ENDIAN1,NONIEEE}; // DeFinition of architecture
TArch Architecture; // Conversion to float depends on architecture
};
class CRandomMother { // Encapsulate random number generator
public:
void RandomInit(uint32 seed); // Initialization
int IRandom(int min,int max); // Get integer random number in desired interval
double Random(); // Get floating point random number
uint32 BRandom(); // Output random bits
CRandomMother(uint32 seed) { // Constructor
RandomInit(seed);}
protected:
uint32 x[5]; // History buffer
};
#endif
void CRandomMersenne::Init0(uint32 seed) {
// Detect computer architecture
union {double f; uint32 i[2];} convert;
convert.f = 1.0;
if (convert.i[1] == 0x3FF00000) Architecture = LITTLE_ENDIAN1;
else if (convert.i[0] == 0x3FF00000) Architecture = BIG_ENDIAN1;
else Architecture = NONIEEE;
// Seed generator
mt[0]= seed;
for (mti=1; mti < MERS_N; mti++) {
mt[mti] = (1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);
}
}
void CRandomMersenne::RandomInit(uint32 seed) {
// Initialize and seed
Init0(seed);
// Randomize some more
for (int i = 0; i < 37; i++) BRandom();
}
void CRandomMersenne::RandomInitByArray(uint32 seeds[],int length) {
// Seed by more than 32 bits
int i,j,k;
// Initialize
Init0(19650218);
if (length <= 0) return;
// Randomize mt[] using whole seeds[] array
i = 1; j = 0;
k = (MERS_N > length ? MERS_N : length);
for (; k; k--) {
mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL)) + seeds[j] + j;
i++; j++;
if (i >= MERS_N) {mt[0] = mt[MERS_N-1]; i=1;}
if (j >= length) j=0;}
for (k = MERS_N-1; k; k--) {
mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL)) - i;
if (++i >= MERS_N) {mt[0] = mt[MERS_N-1]; i=1;}}
mt[0] = 0x80000000UL; // MSB is 1; assuring non-zero initial array
// Randomize some more
mti = 0;
for (int i = 0; i <= MERS_N; i++) BRandom();
}
uint32 CRandomMersenne::BRandom() {
// Generate 32 random bits
uint32 y;
if (mti >= MERS_N) {
// Generate MERS_N words at one time
const uint32 LOWER_MASK = (1LU << MERS_R) - 1; // Lower MERS_R bits
const uint32 UPPER_MASK = 0xFFFFFFFF << MERS_R; // Upper (32 - MERS_R) bits
static const uint32 mag01[2] = {0,MERS_A};
int kk;
for (kk=0; kk < MERS_N-MERS_M; kk++) {
y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
mt[kk] = mt[kk+MERS_M] ^ (y >> 1) ^ mag01[y & 1];}
for (; kk < MERS_N-1; kk++) {
y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
mt[kk] = mt[kk+(MERS_M-MERS_N)] ^ (y >> 1) ^ mag01[y & 1];}
y = (mt[MERS_N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
mt[MERS_N-1] = mt[MERS_M-1] ^ (y >> 1) ^ mag01[y & 1];
mti = 0;
}
y = mt[mti++];
#if 1
// Tempering (May be omitted):
y ^= y >> MERS_U;
y ^= (y << MERS_S) & MERS_B;
y ^= (y << MERS_T) & MERS_C;
y ^= y >> MERS_L;
#endif
return y;
}
double CRandomMersenne::Random() {
// Output random float number in the interval 0 <= x < 1
union {double f; uint32 i[2];} convert;
uint32 r = BRandom(); // Get 32 random bits
// The fastest way to convert random bits to floating point is as follows:
// Set the binary exponent of a floating point number to 1+bias and set
// the mantissa to random bits. This will give a random number in the
// interval [1,2). Then subtract 1.0 to get a random number in the interval
// [0,1). This procedure requires that we kNow how floating point numbers
// are stored. The storing method is tested in function RandomInit and saved
// in the variable Architecture.
// This shortcut allows the compiler to optimize away the following switch
// statement for the most common architectures:
#if defined(_M_IX86) || defined(_M_X64) || defined(__LITTLE_ENDIAN__)
Architecture = LITTLE_ENDIAN1;
#elif defined(__BIG_ENDIAN__)
Architecture = BIG_ENDIAN1;
#endif
switch (Architecture) {
case LITTLE_ENDIAN1:
convert.i[0] = r << 20;
convert.i[1] = (r >> 12) | 0x3FF00000;
return convert.f - 1.0;
case BIG_ENDIAN1:
convert.i[1] = r << 20;
convert.i[0] = (r >> 12) | 0x3FF00000;
return convert.f - 1.0;
case NONIEEE: default: ;
}
// This somewhat slower method works for all architectures,including
// non-IEEE floating point representation:
return (double)r * (1./((double)(uint32)(-1L)+1.));
}
int CRandomMersenne::IRandom(int min,int max) {
// Output random integer in the interval min <= x <= max
// Relative error on frequencies < 2^-32
if (max <= min) {
if (max == min) return min; else return 0x80000000;
}
// Multiply interval with random and truncate
int r = int((max - min + 1) * Random()) + min;
if (r > max) r = max;
return r;
}
int CRandomMersenne::IRandomX(int min,int max) {
// Output random integer in the interval min <= x <= max
// Each output value has exactly the same probability.
// This is obtained by rejecting certain bit values so that the number
// of possible bit values is divisible by the interval length
if (max <= min) {
if (max == min) return min; else return 0x80000000;
}
#ifdef INT64_DEFINED
// 64 bit integers available. Use multiply and shift method
uint32 interval; // Length of interval
uint64 longran; // Random bits * interval
uint32 iran; // Longran / 2^32
uint32 remainder; // Longran % 2^32
interval = uint32(max - min + 1);
if (interval != LastInterval) {
// Interval length has changed. Must calculate rejection limit
// Reject when remainder = 2^32 / interval * interval
// RLimit will be 0 if interval is a power of 2. No rejection then
RLimit = uint32(((uint64)1 << 32) / interval) * interval - 1;
LastInterval = interval;
}
do { // Rejection loop
longran = (uint64)BRandom() * interval;
iran = (uint32)(longran >> 32);
remainder = (uint32)longran;
} while (remainder > RLimit);
// Convert back to signed and return result
return (int32)iran + min;
#else
// 64 bit integers not available. Use modulo method
uint32 interval; // Length of interval
uint32 bran; // Random bits
uint32 iran; // bran / interval
uint32 remainder; // bran % interval
interval = uint32(max - min + 1);
if (interval != LastInterval) {
// Interval length has changed. Must calculate rejection limit
// Reject when iran = 2^32 / interval
// We can't make 2^32 so we use 2^32-1 and correct afterwards
RLimit = (uint32)0xFFFFFFFF / interval;
if ((uint32)0xFFFFFFFF % interval == interval - 1) RLimit++;
}
do { // Rejection loop
bran = BRandom();
iran = bran / interval;
remainder = bran % interval;
} while (iran >= RLimit);
// Convert back to signed and return result
return (int32)remainder + min;
#endif
}
上面这个类的用法很简单：
CRandomMersenne generator(<some_seed>); generator.random(); // random value [0,1] generator.IRandom(a,b); // random value [a,b]
我已经测试了很多次,它比我见过的大多数随机数发生器表现得更好更快.
很多时候,我依赖于这样一个事实：给定种子是确定性的,所以你可以使用它.我将尝试找到该代码的原始来源并将其归功于作者.
编辑：上面代码的作者是Agner Fog,在他的网站上有一个完整的section随机数生成器.代码的所有功劳归于他.