kmath-core/src/commonMain/kotlin/kscience/kmath/structures/NDAlgebra.kt

@@ -4,6 +4,7 @@ import kscience.kmath.operations.Complex
 import kscience.kmath.operations.Field
 import kscience.kmath.operations.Ring
 import kscience.kmath.operations.Space
+import kotlin.native.concurrent.ThreadLocal
 
 /**
  * An exception is thrown when the expected ans actual shape of NDArray differs
@@ -115,6 +116,7 @@ public interface NDField<T, F : Field<T>, N : NDStructure<T>> : Field<N>, NDRing
 
     public operator fun T.div(arg: N): N = map(arg) { divide(it, this@div) }
 
+    @ThreadLocal
     public companion object {
         private val realNDFieldCache: MutableMap<IntArray, RealNDField> = hashMapOf()
 

kmath-core/src/commonMain/kotlin/kscience/kmath/structures/NDStructure.kt

@@ -1,6 +1,7 @@
 package kscience.kmath.structures
 
 import kotlin.jvm.JvmName
+import kotlin.native.concurrent.ThreadLocal
 import kotlin.reflect.KClass
 
 /**
@@ -230,6 +231,7 @@ public class DefaultStrides private constructor(override val shape: IntArray) :
 
     override fun hashCode(): Int = shape.contentHashCode()
 
+    @ThreadLocal
     public companion object {
         private val defaultStridesCache = HashMap<IntArray, Strides>()
 

kmath-core/src/commonTest/kotlin/kscience/kmath/operations/ComplexTest.kt

@@ -2,6 +2,7 @@ package kscience.kmath.operations
 
 import kotlin.test.Test
 import kotlin.test.assertEquals
+import kotlin.test.assertTrue
 
 internal class ComplexTest {
     @Test
@@ -13,7 +14,7 @@ internal class ComplexTest {
 
     @Test
     fun reciprocal() {
-        assertEquals(Complex(0.5, -0.0), 2.toComplex().reciprocal)
+        assertTrue { (Complex(0.5, -0.0) - 2.toComplex().reciprocal).r < 1e-10}
     }
 
     @Test