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-rw-r--r--src/test/random_tests.cpp34
1 files changed, 34 insertions, 0 deletions
diff --git a/src/test/random_tests.cpp b/src/test/random_tests.cpp
index 679e857ce6..9d69d1247d 100644
--- a/src/test/random_tests.cpp
+++ b/src/test/random_tests.cpp
@@ -75,8 +75,42 @@ BOOST_AUTO_TEST_CASE(stdrandom_test)
for (int j = 1; j <= 10; ++j) {
BOOST_CHECK(std::find(test.begin(), test.end(), j) != test.end());
}
+ Shuffle(test.begin(), test.end(), ctx);
+ for (int j = 1; j <= 10; ++j) {
+ BOOST_CHECK(std::find(test.begin(), test.end(), j) != test.end());
+ }
}
}
+/** Test that Shuffle reaches every permutation with equal probability. */
+BOOST_AUTO_TEST_CASE(shuffle_stat_test)
+{
+ FastRandomContext ctx(true);
+ uint32_t counts[5 * 5 * 5 * 5 * 5] = {0};
+ for (int i = 0; i < 12000; ++i) {
+ int data[5] = {0, 1, 2, 3, 4};
+ Shuffle(std::begin(data), std::end(data), ctx);
+ int pos = data[0] + data[1] * 5 + data[2] * 25 + data[3] * 125 + data[4] * 625;
+ ++counts[pos];
+ }
+ unsigned int sum = 0;
+ double chi_score = 0.0;
+ for (int i = 0; i < 5 * 5 * 5 * 5 * 5; ++i) {
+ int i1 = i % 5, i2 = (i / 5) % 5, i3 = (i / 25) % 5, i4 = (i / 125) % 5, i5 = i / 625;
+ uint32_t count = counts[i];
+ if (i1 == i2 || i1 == i3 || i1 == i4 || i1 == i5 || i2 == i3 || i2 == i4 || i2 == i5 || i3 == i4 || i3 == i5 || i4 == i5) {
+ BOOST_CHECK(count == 0);
+ } else {
+ chi_score += ((count - 100.0) * (count - 100.0)) / 100.0;
+ BOOST_CHECK(count > 50);
+ BOOST_CHECK(count < 150);
+ sum += count;
+ }
+ }
+ BOOST_CHECK(chi_score > 58.1411); // 99.9999% confidence interval
+ BOOST_CHECK(chi_score < 210.275);
+ BOOST_CHECK_EQUAL(sum, 12000);
+}
+
BOOST_AUTO_TEST_SUITE_END()