[build statistics] Truncate long values instead of randomization

libraries/tools/kotlin-gradle-statistics/src/common/kotlin/org/jetbrains/kotlin/statistics/metrics/MetricPolicies.kt

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.statistics.metrics
 import org.jetbrains.kotlin.statistics.ValueAnonymizer
 import org.jetbrains.kotlin.statistics.anonymizeComponentVersion
 import org.jetbrains.kotlin.statistics.sha256
+import kotlin.math.abs
 
 
 enum class StringOverridePolicy: IMetricContainerFactory<String> {
@@ -105,10 +106,22 @@ enum class NumberAnonymizationPolicy : ValueAnonymizer<Long> {
         override fun anonymize(t: Long) = t
     },
     RANDOM_10_PERCENT {
-        override fun anonymize(t: Long) = (t + t * 0.1 * Math.random()).toLong()
-    },
-    RANDOM_01_PERCENT {
-        override fun anonymize(t: Long) = (t + t * 0.01 * Math.random()).toLong()
+        override fun anonymize(t: Long): Long {
+            if (abs(t) < 10) return t
+            val sign = if (t < 0)
+                -1
+            else
+                1
+            val absT = t * sign
+            var div: Long = 1
+            while (div * 10 < absT) {
+                div *= 10
+            }
+            return sign * if (absT / div < 2)
+                absT - absT % (div / 10)
+            else
+                absT - absT % div
+        }
     }
 }
 

libraries/tools/kotlin-gradle-statistics/src/test/kotlin/MetricPolicyTest.kt

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+import org.jetbrains.kotlin.statistics.metrics.NumberAnonymizationPolicy.RANDOM_10_PERCENT
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+
+class MetricPolicyTest {
+
+    @Test
+    fun numberAnonimization() {
+        assertEquals(-200, RANDOM_10_PERCENT.anonymize(-234))
+        assertEquals(-120, RANDOM_10_PERCENT.anonymize(-123))
+        assertEquals(-9, RANDOM_10_PERCENT.anonymize(-9))
+        assertEquals(0, RANDOM_10_PERCENT.anonymize(0))
+        assertEquals(1, RANDOM_10_PERCENT.anonymize(1))
+        assertEquals(5, RANDOM_10_PERCENT.anonymize(5))
+        assertEquals(9, RANDOM_10_PERCENT.anonymize(9))
+        assertEquals(10, RANDOM_10_PERCENT.anonymize(10))
+        assertEquals(19, RANDOM_10_PERCENT.anonymize(19))
+        assertEquals(20, RANDOM_10_PERCENT.anonymize(29))
+        assertEquals(120, RANDOM_10_PERCENT.anonymize(123))
+        assertEquals(200, RANDOM_10_PERCENT.anonymize(234))
+    }
+}