[ML] Don't try and correct for sample count when estimating statistic variances for anomaly detection

include/core/CSmallVector.h

@@ -142,6 +142,17 @@ class CSmallVector : public boost::container::small_vector<T, N> {
         return *this;
     }
 
+    std::string toDelimited(const std::string& delimiter = ", ") const {
+        std::string result;
+        for (size_type i = 0; i < this->size(); ++i) {
+            result += std::to_string((*this)[i]);
+            if (i < this->size() - 1) {
+                result += delimiter;
+            }
+        }
+        return result;
+    }
+
 private:
     TBase& baseRef() { return *this; }
     const TBase& baseRef() const { return *this; }

include/maths/common/CBasicStatisticsPersist.h

@@ -14,6 +14,7 @@
 
 #include <core/CHashing.h>
 #include <core/CLogger.h>
+#include <core/CSmallVector.h>
 #include <core/CStringUtils.h>
 
 #include <maths/common/CBasicStatistics.h>
@@ -99,6 +100,11 @@ template<typename T>
 inline std::string typeToString(const CSymmetricMatrix<T>& value) {
     return value.toDelimited();
 }
+
+template<typename T, std::size_t N>
+inline std::string typeToString(const core::CSmallVector<T, N>& value) {
+    return value.toDelimited();
+}
 }
 
 template<typename T, unsigned int ORDER>

include/model/CMetricStatGatherer.h

@@ -242,6 +242,14 @@ using TMinGatherer = CStatGatherer<TMinAccumulator, CLastTime>;
 using TMaxGatherer = CStatGatherer<TMaxAccumulator, CLastTime>;
 using TVarianceGatherer = CStatGatherer<TVarianceAccumulator, CMeanTime>;
 
+template<typename STAT, typename TIME>
+std::ostream& operator<<(std::ostream& os, const CStatGatherer<STAT, TIME>& statGatherer) {
+    os << "CStatGatherer(dim=" << statGatherer.dimension() << ", value="
+       << maths::common::basic_statistics_detail::typeToString(statGatherer.value())
+       << ", count=" << statGatherer.count()
+       << ", varianceScale=" << statGatherer.varianceScale() << ")";
+    return os;
+}
 } // metric_stat_gatherer_detail::
 
 //! \brief Bucket metric statistic gatherer.

include/model/CMetricStatShims.h

@@ -69,6 +69,11 @@ class CSumAccumulator {
     double m_Sum{0.0};
 };
 
+inline std::ostream& operator<<(std::ostream& os, const CSumAccumulator& acc) {
+    os << "CSumAccumulator(" << acc.toDelimited() << ")";
+    return os;
+}
+
 namespace metric_stat_shims {
 using TDouble1Vec = core::CSmallVector<double, 1>;
 using TMeanAccumulator = maths::common::CBasicStatistics::SSampleMean<double>::TAccumulator;