From 0fe785de96ef1162691bff059f3262f6034ca88f Mon Sep 17 00:00:00 2001
From: Ilya Gorbunov <ilya.gorbunov@jetbrains.com>
Date: Tue, 2 Oct 2018 02:37:56 +0300
Subject: [PATCH] Remove the ability to change seed of the default Random

---
 backend.native/tests/runtime/basic/random.kt  | 36 +++++++++----------
 .../tests/runtime/basic/worker_random.kt      |  1 -
 .../src/main/kotlin/kotlin/random/Random.kt   |  8 +----
 3 files changed, 19 insertions(+), 26 deletions(-)

diff --git a/backend.native/tests/runtime/basic/random.kt b/backend.native/tests/runtime/basic/random.kt
index 422d9f126b6..8afeac16175 100644
--- a/backend.native/tests/runtime/basic/random.kt
+++ b/backend.native/tests/runtime/basic/random.kt
@@ -13,14 +13,14 @@ import kotlin.test.*
 /**
  * Tests that setting the same seed make random generate the same sequence
  */
-private inline fun <reified T> testReproducibility(seed: Long, generator: () -> T) {
+private inline fun <reified T> testReproducibility(seed: Long, generator: Random.() -> T) {
     // Reset seed. This will make Random to start a new sequence
-    Random.seed = seed
-    val first = Array<T>(50, { i -> generator() }).toList()
+    val r1 = Random(seed)
+    val first = Array<T>(50, { i -> r1.generator() }).toList()
 
     // Reset seed and try again
-    Random.seed = seed
-    val second = Array<T>(50, { i -> generator() }).toList()
+    val r2 = Random(seed)
+    val second = Array<T>(50, { i -> r2.generator() }).toList()
     assertTrue(first == second, "FAIL: got different sequences of generated values " +
             "first: $first, second: $second")
 }
@@ -28,36 +28,36 @@ private inline fun <reified T> testReproducibility(seed: Long, generator: () ->
 /**
  * Tests that setting seed makes random generate different sequence.
  */
-private inline fun <reified T> testDifference(generator: () -> T) {
-    Random.seed = 12345678L
-    val first = Array<T>(100, { i -> generator() }).toList()
+private inline fun <reified T> testDifference(generator: Random.() -> T) {
+    val r1 = Random(12345678L)
+    val first = Array<T>(100, { i -> r1.generator() }).toList()
 
-    Random.seed = 87654321L
-    val second = Array<T>(100, { i -> generator() }).toList()
+    val r2 = Random(87654321L)
+    val second = Array<T>(100, { i -> r2.generator() }).toList()
     assertTrue(first != second, "FAIL: got the same sequence of generated values " +
             "first: $first, second: $second")
 }
 
 @Test
 fun testInts() {
-    testReproducibility(getTimeMillis(), { Random.nextInt() })
-    testReproducibility(Long.MAX_VALUE, { Random.nextInt() })
+    testReproducibility(getTimeMillis(), { nextInt() })
+    testReproducibility(Long.MAX_VALUE, { nextInt() })
 }
 
 @Test
 fun testLong() {
-    testReproducibility(getTimeMillis(), { Random.nextLong() })
-    testReproducibility(Long.MAX_VALUE, { Random.nextLong() })
+    testReproducibility(getTimeMillis(), { nextLong() })
+    testReproducibility(Long.MAX_VALUE, { nextLong() })
 }
 
 @Test
-fun testDiffInt() = testDifference { Random.nextInt() }
+fun testDiffInt() = testDifference { nextInt() }
 
 @Test
-fun testDiffLong() = testDifference { Random.nextLong() }
+fun testDiffLong() = testDifference { nextLong() }
 
 @Test
 fun testNextInt() {
-    testReproducibility(getTimeMillis(), { Random.nextInt(1000) })
-    testReproducibility(1000L, { Random.nextInt(1024) })
+    testReproducibility(getTimeMillis(), { nextInt(1000) })
+    testReproducibility(1000L, { nextInt(1024) })
 }
diff --git a/backend.native/tests/runtime/basic/worker_random.kt b/backend.native/tests/runtime/basic/worker_random.kt
index f941d397c3e..2aaf1515066 100644
--- a/backend.native/tests/runtime/basic/worker_random.kt
+++ b/backend.native/tests/runtime/basic/worker_random.kt
@@ -19,7 +19,6 @@ fun testRandomWorkers() {
     val attempts = 3
     val results = Array(attempts, { ArrayList<Int>() } )
     for (attempt in 0 until attempts) {
-        Random.seed = seed
         // Produce a list of random numbers in each worker
         val futures = Array(workers.size, { workerIndex ->
             workers[workerIndex].execute(TransferMode.SAFE, { workerIndex }) {
diff --git a/runtime/src/main/kotlin/kotlin/random/Random.kt b/runtime/src/main/kotlin/kotlin/random/Random.kt
index 487341f5dba..ee2b4e56cb5 100644
--- a/runtime/src/main/kotlin/kotlin/random/Random.kt
+++ b/runtime/src/main/kotlin/kotlin/random/Random.kt
@@ -17,9 +17,8 @@ internal object NativeRandom : Random() {
     /**
      * Random generator seed value.
      */
-    var seed: Long
+    private val seed: Long
         get() = _seed.value
-        set(value) = update(mult(value))
 
     private fun mult(value: Long) = (value xor MULTIPLIER) and ((1L shl 48) - 1)
 
@@ -42,8 +41,3 @@ internal actual fun fastLog2(value: Int): Int =
 
 internal actual fun doubleFromParts(hi26: Int, low27: Int): Double =
         (hi26.toLong().shl(27) + low27) / (1L shl 53).toDouble()
-
-// TODO: common stdlib Random hasn't got seed, this is workaround for running K/N tests.
-var Random.seed:Long
-  get() = NativeRandom.seed
-  set(value) { NativeRandom.seed = value }
\ No newline at end of file