118 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// <random>10 11// template <class UIntType, UIntType a, UIntType c, UIntType m>12// class linear_congruential_engine;13 14// result_type operator()();15 16#include <random>17#include <cassert>18 19#include "test_macros.h"20 21int main(int, char**)22{23 typedef unsigned long long T;24 25 // m might overflow, but the overflow is OK so it shouldn't use Schrage's algorithm26 typedef std::linear_congruential_engine<T, 25214903917ull, 1, (1ull << 48)> E1;27 E1 e1;28 // make sure the right algorithm was used29 assert(e1() == 25214903918ull);30 assert(e1() == 205774354444503ull);31 assert(e1() == 158051849450892ull);32 // make sure result is in bounds33 assert(e1() < (1ull << 48));34 assert(e1() < (1ull << 48));35 assert(e1() < (1ull << 48));36 assert(e1() < (1ull << 48));37 assert(e1() < (1ull << 48));38 39 // m might overflow. The overflow is not OK and result will be in bounds40 // so we should use Schrage's algorithm41 typedef std::linear_congruential_engine<T, (1ull << 32), 0, (1ull << 63) + 1ull> E2;42 E2 e2;43 // make sure Schrage's algorithm is used (it would be 0s after the first otherwise)44 assert(e2() == (1ull << 32));45 assert(e2() == (1ull << 63) - 1ull);46 assert(e2() == (1ull << 63) - 0x1ffffffffull);47 // make sure result is in bounds48 assert(e2() < (1ull << 63) + 1);49 assert(e2() < (1ull << 63) + 1);50 assert(e2() < (1ull << 63) + 1);51 assert(e2() < (1ull << 63) + 1);52 assert(e2() < (1ull << 63) + 1);53 54 // m might overflow. The overflow is not OK and result will be in bounds55 // so we should use Schrage's algorithm. m is even56 typedef std::linear_congruential_engine<T, 0x18000001ull, 0x12347ull, (3ull << 56)> E3;57 E3 e3;58 // make sure Schrage's algorithm is used59 assert(e3() == 0x18012348ull);60 assert(e3() == 0x2401b4ed802468full);61 assert(e3() == 0x18051ec400369d6ull);62 // make sure result is in bounds63 assert(e3() < (3ull << 56));64 assert(e3() < (3ull << 56));65 assert(e3() < (3ull << 56));66 assert(e3() < (3ull << 56));67 assert(e3() < (3ull << 56));68 69 // 32-bit case:70 // m might overflow. The overflow is not OK, result will be in bounds,71 // and Schrage's algorithm is incompatible here. Need to use 64 bit arithmetic.72 typedef std::linear_congruential_engine<unsigned, 0x10009u, 0u, 0x7fffffffu> E4;73 E4 e4;74 // make sure enough precision is used75 assert(e4() == 0x10009u);76 assert(e4() == 0x120053u);77 assert(e4() == 0xf5030fu);78 // make sure result is in bounds79 assert(e4() < 0x7fffffffu);80 assert(e4() < 0x7fffffffu);81 assert(e4() < 0x7fffffffu);82 assert(e4() < 0x7fffffffu);83 assert(e4() < 0x7fffffffu);84 85#ifndef TEST_HAS_NO_INT12886 // m might overflow. The overflow is not OK, result will be in bounds,87 // and Schrage's algorithm is incompatible here. Need to use 128 bit arithmetic.88 typedef std::linear_congruential_engine<T, 0x100000001ull, 0ull, (1ull << 61) - 1ull> E5;89 E5 e5;90 // make sure enough precision is used91 assert(e5() == 0x100000001ull);92 assert(e5() == 0x200000009ull);93 assert(e5() == 0xb00000019ull);94 // make sure result is in bounds95 assert(e5() < (1ull << 61) - 1ull);96 assert(e5() < (1ull << 61) - 1ull);97 assert(e5() < (1ull << 61) - 1ull);98 assert(e5() < (1ull << 61) - 1ull);99 assert(e5() < (1ull << 61) - 1ull);100#endif101 102 // m will not overflow so we should not use Schrage's algorithm103 typedef std::linear_congruential_engine<T, 1ull, 1, (1ull << 48)> E6;104 E6 e6;105 // make sure the correct algorithm was used106 assert(e6() == 2ull);107 assert(e6() == 3ull);108 assert(e6() == 4ull);109 // make sure result is in bounds110 assert(e6() < (1ull << 48));111 assert(e6() < (1ull << 48));112 assert(e6() < (1ull << 48));113 assert(e6() < (1ull << 48));114 assert(e6() < (1ull << 48));115 116 return 0;117}118