From 19ec6a57a4bec20fcf14725da84dc125ad539e1f Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@gmail.com>
Date: Thu, 15 Apr 2021 19:39:46 +0300
Subject: [PATCH] Gauss-Legendre working test

---
 .../integration/GaussIntegratorRuleFactory.kt  | 18 +++++++++++-------
 .../kmath/integration/GaussIntegralTest.kt     |  2 +-
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/kmath-functions/src/commonMain/kotlin/space/kscience/kmath/integration/GaussIntegratorRuleFactory.kt b/kmath-functions/src/commonMain/kotlin/space/kscience/kmath/integration/GaussIntegratorRuleFactory.kt
index a3adacc04..678e6bf0a 100644
--- a/kmath-functions/src/commonMain/kotlin/space/kscience/kmath/integration/GaussIntegratorRuleFactory.kt
+++ b/kmath-functions/src/commonMain/kotlin/space/kscience/kmath/integration/GaussIntegratorRuleFactory.kt
@@ -2,7 +2,6 @@ package space.kscience.kmath.integration
 
 import space.kscience.kmath.operations.DoubleField
 import space.kscience.kmath.operations.Field
-import space.kscience.kmath.operations.Ring
 import space.kscience.kmath.structures.*
 import kotlin.jvm.Synchronized
 import kotlin.math.ulp
@@ -27,14 +26,19 @@ public fun <T : Comparable<T>> GaussIntegratorRuleFactory<T>.build(
     range: ClosedRange<T>,
 ): Pair<Buffer<T>, Buffer<T>> {
     val normalized = build(numPoints)
-    val points = with(algebra) {
+    with(algebra) {
         val length = range.endInclusive - range.start
-        normalized.first.map(bufferFactory) {
-            range.start + length / 2 + length * it/2
-        }
-    }
 
-    return points to normalized.second
+        val points = normalized.first.map(bufferFactory) {
+            range.start + length / 2 + length * it / 2
+        }
+
+        val weights = normalized.second.map(bufferFactory) {
+            it * length / 2
+        }
+
+        return points to weights
+    }
 }
 
 
diff --git a/kmath-functions/src/commonTest/kotlin/space/kscience/kmath/integration/GaussIntegralTest.kt b/kmath-functions/src/commonTest/kotlin/space/kscience/kmath/integration/GaussIntegralTest.kt
index 7c33ea73f..5fccd8aa9 100644
--- a/kmath-functions/src/commonTest/kotlin/space/kscience/kmath/integration/GaussIntegralTest.kt
+++ b/kmath-functions/src/commonTest/kotlin/space/kscience/kmath/integration/GaussIntegralTest.kt
@@ -23,7 +23,7 @@ class GaussIntegralTest {
                 0.0
             }
         }
-        assertEquals(20.0, res.value!!, 0.1)
+        assertEquals(20.0, res.value!!, 0.5)
     }