Abstract linear algebra and real value array implementation.

build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.2.41'
+    ext.kotlin_version = '1.2.51'
 
     repositories {
         mavenCentral()

common/src/main/kotlin/scientifik/kmath/structures/LinearAlgrebra.kt

@@ -7,8 +7,10 @@ import scientifik.kmath.operations.SpaceElement
 
 /**
  * The space for linear elements. Supports scalar product alongside with standard linear operations.
+ * @param T type of individual element of the vector or matrix
+ * @param V the type of vector space element
  */
-abstract class LinearSpace<T, V: LinearStructure<out T>>(val rows: Int, val columns: Int, val field: Field<T>) : Space<V> {
+abstract class LinearSpace<T : Any, V : LinearStructure<out T>>(val rows: Int, val columns: Int, val field: Field<T>) : Space<V> {
 
     /**
      * Produce the element of this space
@@ -18,7 +20,7 @@ abstract class LinearSpace<T, V: LinearStructure<out T>>(val rows: Int, val colu
     /**
      * Produce new linear space with given dimensions
      */
-    abstract fun produceSpace(rows: Int, columns: Int): LinearSpace<T,V>
+    abstract fun produceSpace(rows: Int, columns: Int): LinearSpace<T, V>
 
     override val zero: V by lazy {
         produce { _, _ -> field.zero }
@@ -37,9 +39,9 @@ abstract class LinearSpace<T, V: LinearStructure<out T>>(val rows: Int, val colu
      * Dot product
      */
     fun multiply(a: V, b: V): V {
-        if (a.columns != b.rows) {
+        if (a.rows != b.columns) {
             //TODO replace by specific exception
-            throw RuntimeException("Dimension mismatch in vector dot product")
+            error("Dimension mismatch in vector dot product")
         }
         return produceSpace(a.rows, b.columns).produce { i, j ->
             (0..a.columns).asSequence().map { k -> field.multiply(a[i, k], b[k, j]) }.reduce { first, second -> field.add(first, second) }
@@ -52,9 +54,10 @@ abstract class LinearSpace<T, V: LinearStructure<out T>>(val rows: Int, val colu
 /**
  * A matrix-like structure that is not dependent on specific space implementation
  */
-interface LinearStructure<T> {
+interface LinearStructure<T : Any> {
     val rows: Int
     val columns: Int
+
     operator fun get(i: Int, j: Int): T
 
     fun transpose(): LinearStructure<T> {
@@ -66,52 +69,76 @@ interface LinearStructure<T> {
     }
 }
 
-class RealArraySpace(rows: Int, columns: Int) : LinearSpace<Double, RealArray>(rows, columns, DoubleField) {
-    override fun produce(initializer: (Int, Int) -> Double): RealArray {
-        return RealArray(this, initializer)
-    }
+interface Vector<T : Any> : LinearStructure<T> {
+    override val columns: Int
+        get() = 1
 
-    override fun produceSpace(rows: Int, columns: Int): LinearSpace<Double, RealArray> {
-        return RealArraySpace(rows, columns)
-    }
-}
-
-class RealArray(override val context: RealArraySpace, initializer: (Int, Int) -> Double): LinearStructure<Double>, SpaceElement<RealArray> {
-
-    val array: Array<Array<Double>> = Array(context.rows) { i -> Array(context.columns) { j -> initializer(i, j) } }
-
-    override val rows: Int = context.rows
-
-    override val columns: Int = context.columns
-
-    override fun get(i: Int, j: Int): Double {
-        return array[i][j]
-    }
-
-    override val self: RealArray = this
+    operator fun get(i: Int) = get(i, 0)
 }
 
 
-///**
-// * An element of linear algebra with fixed dimension. The linear space allows linear operations on objects of the same dimensions.
-// * Scalar product operations are performed outside space.
-// *
-// * @param E the type of linear object element type.
-// */
-//interface LinearObject<E> : SpaceElement<LinearObject<E>> {
-//    override val context: LinearSpace<>
-//
-//    val rows: Int
-//    val columns: Int
-//    operator fun get(i: Int, j: Int): E
-//
-//    /**
-//     * Get a transposed object with switched dimensions
-//     */
-//    fun transpose(): LinearObject<E>
-//
-//    /**
-//     * Perform scalar multiplication (dot) operation, checking dimensions. The argument object and result both could be outside initial space.
-//     */
-//    operator fun times(other: LinearObject<E>): LinearObject<E>
-//}
+/**
+ * DoubleArray-based implementation of vector space
+ */
+class ArraySpace<T : Any>(rows: Int, columns: Int, field: Field<T>) : LinearSpace<T, LinearStructure<out T>>(rows, columns, field) {
+
+    override fun produce(initializer: (Int, Int) -> T): LinearStructure<T> = ArrayMatrix<T>(this, initializer)
+
+
+    override fun produceSpace(rows: Int, columns: Int): LinearSpace<T, LinearStructure<out T>> {
+        return ArraySpace(rows, columns, field)
+    }
+}
+
+/**
+ * Member of [ArraySpace] which wraps 2-D array
+ */
+class ArrayMatrix<T : Any>(override val context: ArraySpace<T>, initializer: (Int, Int) -> T) : LinearStructure<T>, SpaceElement<LinearStructure<out T>, ArraySpace<T>> {
+
+    val list: List<List<T>> = (0 until rows).map { i -> (0 until columns).map { j -> initializer(i, j) } }
+
+    override val rows: Int get() = context.rows
+
+    override val columns: Int get() = context.columns
+
+    override fun get(i: Int, j: Int): T {
+        return list[i][j]
+    }
+
+    override val self: ArrayMatrix<T> get() = this
+}
+
+
+class ArrayVector<T : Any>(override val context: ArraySpace<T>, initializer: (Int) -> T) : Vector<T>, SpaceElement<LinearStructure<out T>, ArraySpace<T>> {
+
+    init {
+        if (context.columns != 1) {
+            error("Vector must have single column")
+        }
+    }
+
+    val list: List<T> = (0 until context.rows).map(initializer)
+
+
+    override val rows: Int get() = context.rows
+
+    override val columns: Int = 1
+
+    override fun get(i: Int, j: Int): T {
+        return list[i]
+    }
+
+    override val self: ArrayVector<T> get() = this
+
+}
+
+fun <T : Any> vector(size: Int, field: Field<T>, initializer: (Int) -> T) = ArrayVector(ArraySpace(size, 1, field), initializer)
+//TODO replace by primitive array version
+fun realVector(size: Int, initializer: (Int) -> Double) = vector(size, DoubleField, initializer)
+
+fun <T : Any> Array<T>.asVector(field: Field<T>) = vector(size, field) { this[it] }
+//TODO add inferred field from field element
+fun DoubleArray.asVector() = realVector(this.size) { this[it] }
+
+fun <T : Any> matrix(rows: Int, columns: Int, field: Field<T>, initializer: (Int, Int) -> T) = ArrayMatrix<T>(ArraySpace(rows, columns, field), initializer)
+fun realMatrix(rows: Int, columns: Int, initializer: (Int, Int) -> Double) = matrix(rows, columns, DoubleField, initializer)

common/src/main/kotlin/scientifik/kmath/structures/NDArray.kt

@@ -3,6 +3,9 @@ package scientifik.kmath.structures
 import scientifik.kmath.operations.Field
 import scientifik.kmath.operations.FieldElement
 
+/**
+ * An exception is thrown when the expected ans actual shape of NDArray differs
+ */
 class ShapeMismatchException(val expected: List<Int>, val actual: List<Int>) : RuntimeException()
 
 /**
@@ -11,9 +14,11 @@ class ShapeMismatchException(val expected: List<Int>, val actual: List<Int>) : R
  * @param field - operations field defined on individual array element
  * @param T the type of the element contained in NDArray
  */
-abstract class NDField<T>(val shape: List<Int>, val field: Field<T>) : Field<NDArray<T>> {
+abstract class NDField<T>(val shape: List<Int>, private val field: Field<T>) : Field<NDArray<T>> {
+
     /**
      * Create new instance of NDArray using field shape and given initializer
+     * The producer takes list of indices as argument and returns contained value
      */
     abstract fun produce(initializer: (List<Int>) -> T): NDArray<T>
 
@@ -21,6 +26,9 @@ abstract class NDField<T>(val shape: List<Int>, val field: Field<T>) : Field<NDA
         produce { this.field.zero }
     }
 
+    /**
+     * Check the shape of given NDArray and throw exception if it does not coincide with shape of the field
+     */
     private fun checkShape(vararg arrays: NDArray<T>) {
         arrays.forEach {
             if (shape != it.shape) {
@@ -66,13 +74,13 @@ abstract class NDField<T>(val shape: List<Int>, val field: Field<T>) : Field<NDA
 }
 
 
-interface NDArray<T> : FieldElement<NDArray<T>>, Iterable<Pair<List<Int>, T>> {
+interface NDArray<T> : FieldElement<NDArray<T>, NDField<T>>, Iterable<Pair<List<Int>, T>> {
 
     /**
      * The list of dimensions of this NDArray
      */
     val shape: List<Int>
-        get() = (context as NDField<T>).shape
+        get() = context.shape
 
     /**
      * The number of dimentsions for this array

jvm/src/main/kotlin/scientifik/kmath/structures/RealNDArray.kt

@@ -69,7 +69,7 @@ private class RealNDField(shape: List<Int>) : NDField<Double>(shape, DoubleField
         //TODO generate fixed hash code for quick comparison?
 
 
-        override val self: NDArray<Double> = this
+        override val self: NDArray<Double> get() = this
     }
 }
 

jvm/src/test/kotlin/scientifik/kmath/structures/ArrayMatrixTest.kt

@@ -0,0 +1,26 @@
+package scientifik.kmath.structures
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+class ArrayMatrixTest {
+
+    @Test
+    fun testSum() {
+        val vector1 = realVector(5) { it.toDouble() }
+        val vector2 = realVector(5) { 5 - it.toDouble() }
+        val sum = vector1 + vector2
+        assertEquals(5.0, sum[2, 0], 0.1)
+    }
+
+    @Test
+    fun testDot() {
+        val vector1 = realVector(5) { it.toDouble() }
+        val vector2 = realVector(5) { 5 - it.toDouble() }
+        val product = with(vector1.context) {
+            vector1 dot (vector2.transpose())
+        }
+
+        assertEquals(10.0, product[1, 0], 0.1)
+    }
+}