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Fix overflow issue in epee:misc_utils::rolling_median_t and median(), with unit test
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@ -106,6 +106,14 @@ namespace misc_utils
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return true;
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}
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template <typename T>
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T get_mid(const T &a, const T &b)
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{
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//returns the average of two numbers; overflow safe and works with at least all integral and floating point types
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//(a+b)/2 = (a/2) + (b/2) + ((a - 2*(a/2)) + (b - 2*(b/2)))/2
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return (a/2) + (b/2) + ((a - 2*(a/2)) + (b - 2*(b/2)))/2;
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}
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template<class type_vec_type>
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type_vec_type median(std::vector<type_vec_type> &v)
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{
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@ -122,7 +130,7 @@ namespace misc_utils
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return v[n];
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}else
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{//2, 4, 6...
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return (v[n-1] + v[n])/2;
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return get_mid<type_vec_type>(v[n-1],v[n]);
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}
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}
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@ -34,6 +34,8 @@
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#pragma once
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#include "misc_language.h"
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#include <stdlib.h>
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#include <stdint.h>
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@ -226,7 +228,7 @@ public:
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Item v = data[heap[0]];
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if (minCt < maxCt)
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{
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v = (v + data[heap[-1]]) / 2;
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v = get_mid<Item>(v, data[heap[-1]]);
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}
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return v;
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}
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@ -170,6 +170,17 @@ TEST(rolling_median, history_blind)
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}
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}
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TEST(rolling_median, overflow)
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{
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epee::misc_utils::rolling_median_t<uint64_t> m(2);
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uint64_t over_half = static_cast<uint64_t>(3) << static_cast<uint64_t>(62);
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m.insert(over_half);
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m.insert(over_half);
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ASSERT_EQ((over_half + over_half) < over_half, true);
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ASSERT_EQ(over_half, m.median());
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}
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TEST(rolling_median, size)
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{
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epee::misc_utils::rolling_median_t<uint64_t> m(10);
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