kmath-core/src/commonMain/kotlin/scientifik/kmath/expressions/Expression.kt

@@ -58,32 +58,35 @@ internal class DivExpession<T>(val context: Field<T>, val expr: Expression<T>, v
     override fun invoke(arguments: Map<String, T>): T = context.divide(expr.invoke(arguments), second.invoke(arguments))
 }
 
-class ExpressionField<T>(val field: Field<T>) : Field<Expression<T>>, ExpressionContext<T> {
+open class ExpressionSpace<T>(val space: Space<T>) : Space<Expression<T>>, ExpressionContext<T> {
-
+    override val zero: Expression<T> = ConstantExpression(space.zero)
-    override val zero: Expression<T> = ConstantExpression(field.zero)
-
-    override val one: Expression<T> = ConstantExpression(field.one)
 
     override fun const(value: T): Expression<T> = ConstantExpression(value)
 
     override fun variable(name: String, default: T?): Expression<T> = VariableExpression(name, default)
 
-    override fun add(a: Expression<T>, b: Expression<T>): Expression<T> = SumExpression(field, a, b)
+    override fun add(a: Expression<T>, b: Expression<T>): Expression<T> = SumExpression(space, a, b)
 
-    override fun multiply(a: Expression<T>, k: Number): Expression<T> = ConstProductExpession(field, a, k)
+    override fun multiply(a: Expression<T>, k: Number): Expression<T> = ConstProductExpession(space, a, k)
-
-    override fun multiply(a: Expression<T>, b: Expression<T>): Expression<T> = ProductExpression(field, a, b)
-
-    override fun divide(a: Expression<T>, b: Expression<T>): Expression<T> = DivExpession(field, a, b)
 
 
     operator fun Expression<T>.plus(arg: T) = this + const(arg)
     operator fun Expression<T>.minus(arg: T) = this - const(arg)
-    operator fun Expression<T>.times(arg: T) = this * const(arg)
-    operator fun Expression<T>.div(arg: T) = this / const(arg)
 
     operator fun T.plus(arg: Expression<T>) = arg + this
     operator fun T.minus(arg: Expression<T>) = arg - this
+}
+
+
+class ExpressionField<T>(val field: Field<T>) : Field<Expression<T>>, ExpressionSpace<T>(field) {
+    override val one: Expression<T> = ConstantExpression(field.one)
+    override fun multiply(a: Expression<T>, b: Expression<T>): Expression<T> = ProductExpression(field, a, b)
+
+    override fun divide(a: Expression<T>, b: Expression<T>): Expression<T> = DivExpession(field, a, b)
+
+    operator fun Expression<T>.times(arg: T) = this * const(arg)
+    operator fun Expression<T>.div(arg: T) = this / const(arg)
+
     operator fun T.times(arg: Expression<T>) = arg * this
     operator fun T.div(arg: Expression<T>) = arg / this
 }

kmath-histograms/build.gradle.kts

@@ -2,7 +2,6 @@ plugins {
     `npm-multiplatform`
 }
 
-// Just an example how we can collapse nested DSL for simple declarations
 kotlin.sourceSets.commonMain {
     dependencies {
         api(project(":kmath-core"))

kmath-prob/src/commonMain/kotlin/scientifik/kmath/prob/RandomChain.kt

@@ -5,12 +5,9 @@ import scientifik.kmath.chains.Chain
 
 /**
  * A possibly stateful chain producing random values.
- * TODO make random chain properly fork generator
  */
 class RandomChain<out R>(val generator: RandomGenerator, private val gen: suspend RandomGenerator.() -> R) : Chain<R> {
-    private val atomicValue = atomic<R?>(null)
+    override suspend fun next(): R = generator.gen()
-
-    override suspend fun next(): R = generator.gen().also { atomicValue.lazySet(it) }
 
     override fun fork(): Chain<R> = RandomChain(generator.fork(), gen)
 }

kmath-prob/src/commonMain/kotlin/scientifik/kmath/prob/RandomGenerator.kt

@@ -1,5 +1,7 @@
 package scientifik.kmath.prob
 
+import kotlin.random.Random
+
 /**
  * A basic generator
  */
@@ -10,9 +12,30 @@ interface RandomGenerator {
     fun nextBlock(size: Int): ByteArray
 
     /**
-     * Fork the current state of generator
+     * Create a new generator which is independent from current generator (operations on new generator do not affect this one
+     * and vise versa). The statistical properties of new generator should be the same as for this one.
+     * For pseudo-random generator, the fork is keeping the same sequence of numbers for given call order for each run.
+     *
+     * The thread safety of this operation is not guaranteed since it could affect the state of the generator.
      */
     fun fork(): RandomGenerator
 
-    companion object
+    companion object {
+        val default by lazy { DefaultGenerator(Random.nextLong()) }
+    }
+}
+
+class DefaultGenerator(seed: Long?) : RandomGenerator {
+    private val random = seed?.let { Random(it) } ?: Random
+
+    override fun nextDouble(): Double = random.nextDouble()
+
+    override fun nextInt(): Int = random.nextInt()
+
+    override fun nextLong(): Long = random.nextLong()
+
+    override fun nextBlock(size: Int): ByteArray = random.nextBytes(size)
+
+    override fun fork(): RandomGenerator = DefaultGenerator(nextLong())
+
 }