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Last active September 25, 2019 19:08
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gistfile1.txt
+/**
+ * Test uniformity of nextInt32(max)
+ */
+TEST(RandomTest, NextInt32Uniformity) {
+ PseudoRandom prng(10);
+ /* Break the range into sections. */
+ /* Check that all sections get roughly equal # of hits */
+ constexpr int32_t kMax = (int32_t{3} << 29) - 1;
+ constexpr size_t kBuckets = 64;
+ constexpr size_t kNIter = 1'000'000;
+ std::vector<size_t> hist(kBuckets);
+ for (size_t i = 0; i < kNIter; ++i) {
+ auto next = prng.nextInt32(kMax);
+ ASSERT_GTE(next, 0);
+ ASSERT_LTE(next, kMax);
+ ++hist[double(next) * kBuckets / (kMax+1)];
+ }
+ if (1) { // super verbose
+ for (size_t i = 0; i < hist.size(); ++i) {
+ std::string stars(hist[i]/256, '*');
+ unittest::log() << format(FMT_STRING(" [{:4}] {:4} : {}"),
+ i, hist[i], stars);
+ }
+ }
+ constexpr double mu = kNIter / kBuckets;
+ constexpr double muSqInv = 1. / (mu * mu);
+ for (size_t i = 0; i < hist.size(); ++i) {
+ double dev = std::sqrt(std::pow(hist[i] - mu, 2) * muSqInv);
+ std::string stars(hist[i]/256, '*');
+ ASSERT_LT(dev, 0.1) << format(FMT_STRING("hist[{}]={}, mu={}"), i, hist[i], mu);
+ }
+}
+
2019-09-25T13:33:56.672-0400 I - [main] going to run test: NextInt32Uniformity
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Raw
gistfile2.txt
Catchpoint 5 (call to syscall read), 0x00007ffff4e0534e in __libc_read (fd=6, buf=buf@entry=0x7fffeee07820, nbytes=nbytes@entry=8191) at ../sysdeps/unix/sysv/linux/read.c:27
27 ../sysdeps/unix/sysv/linux/read.c: No such file or directory.
(gdb) bt
#0 0x00007ffff4e0534e in __libc_read (fd=6, buf=buf@entry=0x7fffeee07820, nbytes=nbytes@entry=8191) at ../sysdeps/unix/sysv/linux/read.c:27
#1 0x00007ffff7916287 in std::__basic_file<char>::xsgetn (this=this@entry=0x7fffeee004d8, __s=0x7fffeee07820 '\253' <repeats 200 times>..., __n=__n@entry=8191) at basic_file.cc:285
#2 0x00007ffff793ff30 in std::basic_filebuf<char, std::char_traits<char> >::underflow (this=0x7fffeee00470) at /home/billy/dev/10gen/toolchain-builder/tmp/build-gcc-v3.sh-sRY/build/x86_64-mongodb-linux/libstdc++-v3/include/bits/char_traits.h:350
#3 0x00007ffff78ee576 in std::basic_streambuf<char, std::char_traits<char> >::uflow (this=0x7fffeee00470) at /home/billy/dev/10gen/toolchain-builder/tmp/build-gcc-v3.sh-sRY/build/x86_64-mongodb-linux/libstdc++-v3/include/streambuf:707
#4 std::basic_streambuf<char, std::char_traits<char> >::xsgetn (this=this@entry=0x7fffeee00470, __s=__s@entry=0x7fffffffd468 " \362\333\356\377\177", __n=__n@entry=8)
at /home/billy/dev/10gen/toolchain-builder/tmp/build-gcc-v3.sh-sRY/build/x86_64-mongodb-linux/libstdc++-v3/include/bits/streambuf.tcc:64
#5 0x00007ffff79409e3 in std::basic_filebuf<char, std::char_traits<char> >::xsgetn (this=0x7fffeee00470, __s=0x7fffffffd468 " \362\333\356\377\177", __n=8)
at /home/billy/dev/10gen/toolchain-builder/tmp/build-gcc-v3.sh-sRY/build/x86_64-mongodb-linux/libstdc++-v3/include/bits/codecvt.h:210
#6 0x00007ffff78e989d in std::basic_streambuf<char, std::char_traits<char> >::sgetn (__n=8, __s=0x7fffffffd468 " \362\333\356\377\177", this=<optimized out>)
at /home/billy/dev/10gen/toolchain-builder/tmp/build-gcc-v3.sh-sRY/build/x86_64-mongodb-linux/libstdc++-v3/include/streambuf:364
#7 std::istream::read (this=0x7fffeee00460, __s=0x7fffffffd468 " \362\333\356\377\177", __n=8) at /home/billy/dev/10gen/toolchain-builder/tmp/build-gcc-v3.sh-sRY/build/x86_64-mongodb-linux/libstdc++-v3/include/bits/istream.tcc:667
#8 0x00007ffff7c9b2be in mongo::random_detail::SecureUrbg::State::operator() (this=0x7fffeee00460) at src/mongo/platform/random.cpp:127
#9 0x00007ffff7c9b02c in mongo::random_detail::SecureUrbg::operator() (this=0x7fffeedbf220) at src/mongo/platform/random.cpp:139
#10 0x00005555557397ee in std::uniform_int_distribution<long>::operator()<mongo::random_detail::SecureUrbg> (this=0x7fffffffd5f0, __urng=..., __param=...) at /opt/mongodbtoolchain/stow/gcc-v3.sFn/include/c++/8.2.0/bits/uniform_int_dist.h:275
#11 0x0000555555736bd3 in std::uniform_int_distribution<long>::operator()<mongo::random_detail::SecureUrbg> (this=0x7fffffffd5f0, __urng=...) at /opt/mongodbtoolchain/stow/gcc-v3.sFn/include/c++/8.2.0/bits/uniform_int_dist.h:166
#12 0x0000555555733f35 in mongo::RandomBase<mongo::random_detail::SecureUrbg>::_nextAny<long> (this=0x7fffeedbf220) at src/mongo/platform/random.h:137
#13 0x000055555572f578 in mongo::RandomBase<mongo::random_detail::SecureUrbg>::nextInt64 (this=0x7fffeedbf220) at src/mongo/platform/random.h:120
#14 0x00007ffff7c7d232 in mongo::_mongoInitializerFunction_OIDGeneration (context=0x7fffffffd7b0) at src/mongo/bson/oid.cpp:58
#15 0x00007ffff7f9935b in std::_Function_handler<mongo::Status (mongo::InitializerContext*), mongo::Status (*)(mongo::InitializerContext*)>::_M_invoke(std::_Any_data const&, mongo::InitializerContext*&&) (__functor=..., __args#0=@0x7fffffffd6f8: 0x7fffffffd7b0)
at /opt/mongodbtoolchain/stow/gcc-v3.sFn/include/c++/8.2.0/bits/std_function.h:283
#16 0x00007ffff7c28598 in std::function<mongo::Status (mongo::InitializerContext*)>::operator()(mongo::InitializerContext*) const (this=0x7fffeede5400, __args#0=0x7fffffffd7b0) at /opt/mongodbtoolchain/stow/gcc-v3.sFn/include/c++/8.2.0/bits/std_function.h:687
#17 0x00007ffff7c27481 in mongo::Initializer::executeInitializers (this=0x7ffff7dbb6e0 <mongo::getGlobalInitializer()::theGlobalInitializer>, args=..., env=...) at src/mongo/base/initializer.cpp:71
#18 0x00007ffff7c278ee in mongo::runGlobalInitializers (args=..., env=...) at src/mongo/base/initializer.cpp:114
#19 0x00007ffff7c27b26 in mongo::runGlobalInitializers (argc=3, argv=0x7fffffffddb8, envp=0x7fffffffdee0) at src/mongo/base/initializer.cpp:133
#20 0x00007ffff7c27c8b in mongo::runGlobalInitializersOrDie (argc=3, argv=0x7fffffffddb8, envp=0x7fffffffddd8) at src/mongo/base/initializer.cpp:141
#21 0x00007ffff7fe51f3 in main (argc=3, argv=0x7fffffffddb8, envp=0x7fffffffddd8) at src/mongo/unittest/unittest_main.cpp:52
#22 0x00007ffff4a24b97 in __libc_start_main (main=0x7ffff7fe519c <main(int, char**, char**)>, argc=3, argv=0x7fffffffddb8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffdda8) at ../csu/libc-start.c:310
#23 0x00005555556f9cea in _start ()
(gdb)
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