tbb::internal::FastRandom Class Reference

A fast random number generator. More...

#include <tbb_misc.h>

Collaboration diagram for tbb::internal::FastRandom:

Public Member Functions
unsigned short	get ()
	Get a random number. More...
unsigned short	get (unsigned &seed)
	Get a random number for the given seed; update the seed for next use. More...
	FastRandom (void *unique_ptr)
	Construct a random number generator. More...
	FastRandom (uint32_t seed)
	FastRandom (uint64_t seed)
template<typename T >
void	init (T seed)
void	init (uint64_t seed, int_to_type< 8 >)
void	init (uint32_t seed, int_to_type< 4 >)

Private Attributes
unsigned	x
unsigned	c

Static Private Attributes
static const unsigned	a = 0x9e3779b1

Detailed Description

A fast random number generator.

Uses linear congruential method.

Definition at line 134 of file tbb_misc.h.

Constructor & Destructor Documentation

FastRandom() [1/3]

tbb::internal::FastRandom::FastRandom ( void *  unique_ptr )

inline

Construct a random number generator.

Definition at line 156 of file tbb_misc.h.

{ init(uintptr_t(unique_ptr)); }

References init().

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FastRandom() [2/3]

tbb::internal::FastRandom::FastRandom ( uint32_t  seed )

inline

Definition at line 157 of file tbb_misc.h.

{ init(seed); }

References init().

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FastRandom() [3/3]

tbb::internal::FastRandom::FastRandom ( uint64_t  seed )

inline

Definition at line 158 of file tbb_misc.h.

{ init(seed); }

References init().

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Member Function Documentation

get() [1/2]

unsigned short tbb::internal::FastRandom::get ( )

inline

Get a random number.

Definition at line 145 of file tbb_misc.h.

                         {
        return get(x);
    }

References x.

Referenced by tbb::internal::task_stream< num_priority_levels >::push().

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get() [2/2]

unsigned short tbb::internal::FastRandom::get ( unsigned &  seed )

inline

Get a random number for the given seed; update the seed for next use.

Definition at line 149 of file tbb_misc.h.

                                         {
        unsigned short r = (unsigned short)(seed>>16);
        __TBB_ASSERT(c&1, "c must be odd for big rng period");
        seed = seed*a+c;
        return r;
    }

References __TBB_ASSERT, a, and c.

init() [1/3]

template<typename T >

void tbb::internal::FastRandom::init ( T  seed )

inline

Definition at line 160 of file tbb_misc.h.

                        {
        init(seed,int_to_type<sizeof(seed)>());
    }

Referenced by FastRandom(), and init().

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init() [2/3]

void tbb::internal::FastRandom::init ( uint64_t  seed, int_to_type< 8 >    )

inline

Definition at line 163 of file tbb_misc.h.

                                                {
        init(uint32_t((seed>>32)+seed), int_to_type<4>());
    }

References init().

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init() [3/3]

void tbb::internal::FastRandom::init ( uint32_t  seed, int_to_type< 4 >    )

inline

Definition at line 166 of file tbb_misc.h.

                                               {
#if __TBB_OLD_PRIMES_RNG
        x = seed;
        a = GetPrime( seed );
#else
        // threads use different seeds for unique sequences
        c = (seed|1)*0xba5703f5; // c must be odd, shuffle by a prime number
        x = c^(seed>>1); // also shuffle x for the first get() invocation
#endif
    }

References a, c, tbb::internal::GetPrime(), and x.

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Member Data Documentation

a

const unsigned tbb::internal::FastRandom::a = 0x9e3779b1

staticprivate

Definition at line 141 of file tbb_misc.h.

Referenced by get(), and init().

c

unsigned tbb::internal::FastRandom::c

private

Definition at line 140 of file tbb_misc.h.

Referenced by get(), and init().

x

unsigned tbb::internal::FastRandom::x

private

Definition at line 140 of file tbb_misc.h.

Referenced by get(), and init().

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

• tbb_misc.h