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Merge #18781: Add templated GetRandDuration<>

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0000ea3265 test: Add test for GetRandMillis and GetRandMicros (MarcoFalke)
fa0e5b89cf Add templated GetRandomDuration<> (MarcoFalke)

Pull request description:

  A naive implementation of this template is dangerous, because the call site might accidentally omit the template parameter:

  ```cpp
  template <typename D>
  D GetRandDur(const D& duration_max)
  {
      return D{GetRand(duration_max.count())};
  }

  BOOST_AUTO_TEST_CASE(util_time_GetRandTime)
  {
      std::chrono::seconds rand_hour = GetRandDur(std::chrono::hours{1});
      // Want seconds to be in range [0..1hour), but always get zero :((((
      BOOST_CHECK_EQUAL(rand_hour.count(), 0);
  }
  ```

  Luckily `std::common_type` is already specialised in the standard lib for `std::chrono::duration` (https://en.cppreference.com/w/cpp/chrono/duration/common_type). And its effect seem to be that the call site must always specify the template argument explicitly.

  So instead of implementing the function for each duration type by hand, replace it with a templated version that is safe to use.

ACKs for top commit:
  laanwj:
    Code review ACK 0000ea3265
  promag:
    Code review ACK 0000ea3265.
  jonatack:
    ACK 0000ea3 thanks for the improved documentation. Code review, built, ran `src/test/test_bitcoin -t random_tests -l test_suite` for the new unit tests, `git diff fa05a4c 0000ea3` since previous review:
  hebasto:
    ACK 0000ea3265 with non-blocking [nit](https://github.com/bitcoin/bitcoin/pull/18781#discussion_r424924671).

Tree-SHA512: e89d46e31452be6ea14269ecbbb2cdd9ae83b4412cd14dff7d1084283092722a2f847cb501e8054394e4a3eff852f9c87f6d694fd008b3f7e8458cb5a3068af7
This commit is contained in:
MarcoFalke
2020-05-15 08:58:42 -04:00
parent e2f6866cca 0000ea3265
commit 951870807e
3 changed files with 21 additions and 18 deletions
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7
src/test/random_tests.cpp
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@@ -28,6 +28,8 @@ BOOST_AUTO_TEST_CASE(fastrandom_tests)
for (int i = 10; i > 0; --i) {
BOOST_CHECK_EQUAL(GetRand(std::numeric_limits<uint64_t>::max()), uint64_t{10393729187455219830U});
BOOST_CHECK_EQUAL(GetRandInt(std::numeric_limits<int>::max()), int{769702006});
BOOST_CHECK_EQUAL(GetRandMicros(std::chrono::hours{1}).count(), 2917185654);
BOOST_CHECK_EQUAL(GetRandMillis(std::chrono::hours{1}).count(), 2144374);
}
BOOST_CHECK_EQUAL(ctx1.rand32(), ctx2.rand32());
BOOST_CHECK_EQUAL(ctx1.rand32(), ctx2.rand32());
@@ -47,6 +49,8 @@ BOOST_AUTO_TEST_CASE(fastrandom_tests)
for (int i = 10; i > 0; --i) {
BOOST_CHECK(GetRand(std::numeric_limits<uint64_t>::max()) != uint64_t{10393729187455219830U});
BOOST_CHECK(GetRandInt(std::numeric_limits<int>::max()) != int{769702006});
BOOST_CHECK(GetRandMicros(std::chrono::hours{1}) != std::chrono::microseconds{2917185654});
BOOST_CHECK(GetRandMillis(std::chrono::hours{1}) != std::chrono::milliseconds{2144374});
}
{
FastRandomContext ctx3, ctx4;
@@ -87,7 +91,7 @@ BOOST_AUTO_TEST_CASE(stdrandom_test)
BOOST_CHECK(x >= 3);
BOOST_CHECK(x <= 9);
std::vector<int> test{1,2,3,4,5,6,7,8,9,10};
std::vector<int> test{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
std::shuffle(test.begin(), test.end(), ctx);
for (int j = 1; j <= 10; ++j) {
BOOST_CHECK(std::find(test.begin(), test.end(), j) != test.end());
@@ -97,7 +101,6 @@ BOOST_AUTO_TEST_CASE(stdrandom_test)
BOOST_CHECK(std::find(test.begin(), test.end(), j) != test.end());
}
}
}
/** Test that Shuffle reaches every permutation with equal probability. */