79 lines
2.6 KiB
C
79 lines
2.6 KiB
C
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/*
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Copyright (c) 2005-2020 Intel Corporation
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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#ifndef FAST_RANDOM_H_
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#define FAST_RANDOM_H_
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namespace utility{
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//------------------------------------------------------------------------
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// FastRandom
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//------------------------------------------------------------------------
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namespace internal{
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size_t GetPrime ( size_t seed );
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}
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//! A fast random number generator.
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/** Uses linear congruential method. */
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class FastRandom {
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size_t x, a;
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public:
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//! Get a random number.
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unsigned short get() {
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return get(x);
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}
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//! Get a random number for the given seed; update the seed for next use.
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unsigned short get( size_t& seed ) {
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unsigned short r = (unsigned short)(seed>>16);
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seed = seed*a+1;
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return r;
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}
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//! Construct a random number generator.
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FastRandom( size_t seed ) {
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x = seed*internal::GetPrime(seed);
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a = internal::GetPrime(x);
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}
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};
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}
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namespace utility {
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namespace internal{
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//! Table of primes used by fast random-number generator (FastRandom).
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static const unsigned Primes[] = {
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0x9e3779b1, 0xffe6cc59, 0x2109f6dd, 0x43977ab5,
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0xba5703f5, 0xb495a877, 0xe1626741, 0x79695e6b,
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0xbc98c09f, 0xd5bee2b3, 0x287488f9, 0x3af18231,
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0x9677cd4d, 0xbe3a6929, 0xadc6a877, 0xdcf0674b,
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0xbe4d6fe9, 0x5f15e201, 0x99afc3fd, 0xf3f16801,
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0xe222cfff, 0x24ba5fdb, 0x0620452d, 0x79f149e3,
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0xc8b93f49, 0x972702cd, 0xb07dd827, 0x6c97d5ed,
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0x085a3d61, 0x46eb5ea7, 0x3d9910ed, 0x2e687b5b,
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0x29609227, 0x6eb081f1, 0x0954c4e1, 0x9d114db9,
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0x542acfa9, 0xb3e6bd7b, 0x0742d917, 0xe9f3ffa7,
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0x54581edb, 0xf2480f45, 0x0bb9288f, 0xef1affc7,
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0x85fa0ca7, 0x3ccc14db, 0xe6baf34b, 0x343377f7,
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0x5ca19031, 0xe6d9293b, 0xf0a9f391, 0x5d2e980b,
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0xfc411073, 0xc3749363, 0xb892d829, 0x3549366b,
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0x629750ad, 0xb98294e5, 0x892d9483, 0xc235baf3,
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0x3d2402a3, 0x6bdef3c9, 0xbec333cd, 0x40c9520f
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};
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size_t GetPrime ( size_t seed ) {
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return Primes[seed%(sizeof(Primes)/sizeof(Primes[0]))];
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}
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}
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}
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#endif /* FAST_RANDOM_H_ */
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