PCG32 Struct Reference

Public Types
typedef unsigned	result_type

Public Member Functions
	PCG32 (const uint64_t s, const uint64_t ss=b)
void	seed (const uint64_t s, const uint64_t ss=b)
PCG32 &	index (const uint64_t i)
unsigned	sample ()
unsigned	sample_range (const unsigned range)
unsigned	operator() ()

Static Public Member Functions
static constexpr unsigned	min ()
static constexpr unsigned	max ()

Public Attributes
uint64_t	x
uint64_t	x0
uint64_t	key

Static Public Attributes
static constexpr uint64_t	a = 0x5851f42d4c957f2d
static constexpr uint64_t	b = 0xda3e39cb94b95bdb

Detailed Description

Definition at line 12 of file pcg.h.

Member Typedef Documentation

result_type

typedef unsigned PCG32::result_type

Definition at line 82 of file pcg.h.

Constructor & Destructor Documentation

PCG32() [1/2]

PCG32::PCG32 ( )

inline

Definition at line 14 of file pcg.h.

: x(), x0(), key() { seed(0x853c49e6748fea9b, b); }

PCG32() [2/2]

PCG32::PCG32 ( const uint64_t s, const uint64_t ss = b )

inline

Definition at line 15 of file pcg.h.

: x(), x0(), key() { seed(s, ss); }

Member Function Documentation

seed()

void PCG32::seed ( const uint64_t s, const uint64_t ss = b )

inline

Definition at line 17 of file pcg.h.

    {
        key= (ss << 1) | 1;
        
        x= key + s;
        sample();
        x0= x;
    }

index()

PCG32 & PCG32::index ( const uint64_t i )

inline

Definition at line 26 of file pcg.h.

    {
        // advance to sample index
        // http://www.pcg-random.org implementation
        uint64_t tmul= a;
        uint64_t tadd= key;
        uint64_t mul= 1;
        uint64_t add= 0;
        
        uint64_t delta= i;
        while(delta)
        {
            if(delta & 1)
            {
                mul= mul * tmul;
                add= add * tmul + tadd;
            }
            
            tadd= tmul * tadd + tadd;
            tmul= tmul * tmul;
            delta= delta >> 1;
        }
        
        x= mul * x0 + add;
        return *this;
    }

sample()

unsigned PCG32::sample ( )

inline

Definition at line 53 of file pcg.h.

    {
        uint64_t xx= x;
        x= a*x + key;
        
        // hash(x)
        uint32_t tmp= ((xx >> 18u) ^ xx) >> 27u;
        uint32_t r= xx >> 59u;
        return (tmp >> r) | (tmp << ((~r + 1u) & 31));
    }

sample_range()

unsigned PCG32::sample_range ( const unsigned range )

inline

Definition at line 64 of file pcg.h.

    {
        // Efficiently Generating a Number in a Range
        // cf http://www.pcg-random.org/posts/bounded-rands.html
        unsigned divisor= ((-range) / range) + 1; // (2^32) / range
        if(divisor == 0) return 0;
        
        while(true)
        {
            unsigned x= sample() / divisor;
            if(x < range) return x;
        }
    }

operator()()

unsigned PCG32::operator() ( )

inline

Definition at line 79 of file pcg.h.

{ return sample(); }

min()

constexpr unsigned PCG32::min ( )

inlinestaticconstexpr

Definition at line 80 of file pcg.h.

{ return 0; }

max()

constexpr unsigned PCG32::max ( )

inlinestaticconstexpr

Definition at line 81 of file pcg.h.

{ return ~unsigned(0); }

Member Data Documentation

a

uint64_t PCG32::a = 0x5851f42d4c957f2d

staticconstexpr

Definition at line 84 of file pcg.h.

b

uint64_t PCG32::b = 0xda3e39cb94b95bdb

staticconstexpr

Definition at line 85 of file pcg.h.

x

uint64_t PCG32::x

Definition at line 87 of file pcg.h.

x0

uint64_t PCG32::x0

Definition at line 88 of file pcg.h.

key

uint64_t PCG32::key

Definition at line 89 of file pcg.h.

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The documentation for this struct was generated from the following file:

• src/gKit/pcg.h