From 957ca005886fb29489de483068761a87e0c9c6b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20=C5=9Aliwak?= <kamil.sliwak@codepoets.it>
Date: Fri, 14 Feb 2020 23:42:01 +0100
Subject: [PATCH] [yul-phaser] Common: Add mean() and meanSquaredError()

---
 test/yulPhaser/Common.h       | 51 +++++++++++++++++++++++++++++++++++
 test/yulPhaser/CommonTest.cpp | 29 ++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/test/yulPhaser/Common.h b/test/yulPhaser/Common.h
index 8a7bc9afe..a5881d329 100644
--- a/test/yulPhaser/Common.h
+++ b/test/yulPhaser/Common.h
@@ -27,3 +27,54 @@
  */
 
 #pragma once
+
+#include <cassert>
+#include <vector>
+
+namespace solidity::phaser::test
+{
+
+// STATISTICAL UTILITIES
+
+/// Calculates the mean value of a series of samples given in a vector.
+///
+/// Supports any integer and real type as a convenience but the precision of the result is limited
+/// to the precision of type @a double as all the values are internally converted to it.
+///
+/// This is a very simple, naive implementation that's more than enough for tests where we usually
+/// deal with relatively short sequences of small, positive integers. It's not numerically stable
+/// in more complicated cases. Don't use in production.
+template <typename T>
+double mean(std::vector<T> const& _samples)
+{
+	assert(_samples.size() > 0);
+
+	double sum = 0;
+	for (T const& sample: _samples)
+		sum += static_cast<double>(sample);
+
+	return sum / _samples.size();
+}
+
+/// Calculates the sum of squared differences between @a _expectedValue and the values of a series
+/// of samples given in a vector.
+///
+/// Supports any integer and real type as a convenience but the precision of the result is limited
+/// to the precision of type @a double as all the values are internally converted to it.
+///
+/// This is a very simple, naive implementation that's more than enough for tests where we usually
+/// deal with relatively short sequences of small, positive integers. It's not numerically stable
+/// in more complicated cases. Don't use in production.
+template <typename T>
+double meanSquaredError(std::vector<T> const& _samples, double _expectedValue)
+{
+	assert(_samples.size() > 0);
+
+	double sumOfSquaredDifferences = 0;
+	for (T const& sample: _samples)
+		sumOfSquaredDifferences += (sample - _expectedValue) * (sample - _expectedValue);
+
+	return sumOfSquaredDifferences / _samples.size();
+}
+
+}
diff --git a/test/yulPhaser/CommonTest.cpp b/test/yulPhaser/CommonTest.cpp
index 55ddc4633..f86d963bd 100644
--- a/test/yulPhaser/CommonTest.cpp
+++ b/test/yulPhaser/CommonTest.cpp
@@ -15,14 +15,43 @@
 	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <test/yulPhaser/Common.h>
+
 #include <boost/test/unit_test.hpp>
 
+using namespace boost::test_tools;
+
 namespace solidity::phaser::test
 {
 
 BOOST_AUTO_TEST_SUITE(Phaser)
 BOOST_AUTO_TEST_SUITE(CommonTest)
 
+BOOST_AUTO_TEST_CASE(mean_should_calculate_statistical_mean)
+{
+	BOOST_TEST(mean<int>({0}) == 0.0);
+	BOOST_TEST(mean<int>({0, 0, 0, 0}) == 0.0);
+	BOOST_TEST(mean<int>({5, 5, 5, 5}) == 5.0);
+	BOOST_TEST(mean<int>({0, 1, 2, 3}) == 1.5);
+	BOOST_TEST(mean<int>({-4, -3, -2, -1, 0, 1, 2, 3}) == -0.5);
+
+	BOOST_TEST(mean<double>({1.3, 1.1, 0.0, 1.5, 1.1, 2.0, 1.5, 1.5}) == 1.25);
+}
+
+BOOST_AUTO_TEST_CASE(meanSquaredError_should_calculate_average_squared_difference_between_samples_and_expected_value)
+{
+	BOOST_TEST(meanSquaredError<int>({0}, 0.0) == 0.0);
+	BOOST_TEST(meanSquaredError<int>({0}, 1.0) == 1.0);
+	BOOST_TEST(meanSquaredError<int>({0, 0, 0, 0}, 0.0) == 0.0);
+	BOOST_TEST(meanSquaredError<int>({0, 0, 0, 0}, 1.0) == 1.0);
+	BOOST_TEST(meanSquaredError<int>({0, 0, 0, 0}, 2.0) == 4.0);
+	BOOST_TEST(meanSquaredError<int>({5, 5, 5, 5}, 1.0) == 16.0);
+	BOOST_TEST(meanSquaredError<int>({0, 1, 2, 3}, 2.0) == 1.5);
+	BOOST_TEST(meanSquaredError<int>({-4, -3, -2, -1, 0, 1, 2, 3}, -4.0) == 17.5);
+
+	BOOST_TEST(meanSquaredError<double>({1.3, 1.1, 0.0, 1.5, 1.1, 2.0, 1.5, 1.5}, 1.0) == 0.3575, tolerance(0.0001));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 BOOST_AUTO_TEST_SUITE_END()