From d17a3ac6eff3d6c62e99af7e030010846afd413b Mon Sep 17 00:00:00 2001
From: zhelenskiy <zhelenskiy2000@yandex.ru>
Date: Mon, 10 May 2021 18:24:13 +0300
Subject: [PATCH] Further optimization of power is added

---
 .../kotlin/space/kscience/kmath/operations/Algebra.kt           | 1 +
 .../kotlin/space/kscience/kmath/operations/BigIntAlgebraTest.kt | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/operations/Algebra.kt b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/operations/Algebra.kt
index 49861b543..f7c021998 100644
--- a/kmath-core/src/commonMain/kotlin/space/kscience/kmath/operations/Algebra.kt
+++ b/kmath-core/src/commonMain/kotlin/space/kscience/kmath/operations/Algebra.kt
@@ -254,6 +254,7 @@ public interface Ring<T> : Group<T>, RingOperations<T> {
     public fun T.pow(exponent: ULong): T = when {
         this == zero && exponent > 0UL -> zero
         this == one -> this
+        this == -one -> powWithoutOptimization(exponent % 2UL)
         else -> powWithoutOptimization(exponent)
     }
 
diff --git a/kmath-core/src/commonTest/kotlin/space/kscience/kmath/operations/BigIntAlgebraTest.kt b/kmath-core/src/commonTest/kotlin/space/kscience/kmath/operations/BigIntAlgebraTest.kt
index 05b73b49d..90cd29758 100644
--- a/kmath-core/src/commonTest/kotlin/space/kscience/kmath/operations/BigIntAlgebraTest.kt
+++ b/kmath-core/src/commonTest/kotlin/space/kscience/kmath/operations/BigIntAlgebraTest.kt
@@ -25,7 +25,7 @@ internal class BigIntAlgebraTest {
     @Test
     fun testKBigIntegerRingPow() {
         BigIntField {
-            for (num in 0..5)
+            for (num in -5..5)
                 for (exponent in 0UL..10UL)
                     assertEquals(
                         num.toDouble().pow(exponent.toInt()).toLong().toBigInt(),