Add README.md for kmath-nd4j

kmath-nd4j/README.md

@@ -0,0 +1,73 @@
+# ND4J NDStructure implementation (`kmath-nd4j`)
+
+This subproject implements the following features:
+
+- NDStructure wrapper for INDArray.
+- Optimized NDRing implementation for INDArray storing Ints.
+- Optimized NDField implementation for INDArray storing Floats and Doubles.
+
+> #### Artifact:
+> This module is distributed in the artifact `scientifik:kmath-nd4j:0.1.4-dev-8`.
+> 
+> **Gradle:**
+>
+> ```gradle
+> repositories {
+>     maven { url 'https://dl.bintray.com/mipt-npm/scientifik' }
+>     maven { url 'https://dl.bintray.com/mipt-npm/dev' }
+> }
+> 
+> dependencies {
+>     implementation 'scientifik:kmath-nd4j:0.1.4-dev-8'
+> }
+> ```
+> **Gradle Kotlin DSL:**
+>
+> ```kotlin
+> repositories {
+>     maven("https://dl.bintray.com/mipt-npm/scientifik")
+>     maven("https://dl.bintray.com/mipt-npm/dev")
+> }
+> 
+> dependencies {
+>     implementation("scientifik:kmath-nd4j:0.1.4-dev-8")
+> }
+> ```
+>
+
+## Examples
+
+NDStructure wrapper for INDArray:
+
+```kotlin
+import org.nd4j.linalg.factory.*
+import scientifik.kmath.nd4j.*
+import scientifik.kmath.structures.*
+
+val array = Nd4j.ones(2, 2)!!.asRealStructure()
+println(array[0, 0]) // 1.0
+array[intArrayOf(0, 0)] = 24.0
+println(array[0, 0]) // 24.0
+```
+
+Fast element-wise arithmetics for INDArray:
+
+```kotlin
+import org.nd4j.linalg.factory.*
+import scientifik.kmath.nd4j.*
+import scientifik.kmath.operations.*
+
+val field = RealINDArrayField(intArrayOf(2, 2))
+val array = Nd4j.rand(2, 2)!!.asRealStructure()
+
+val res = field {
+    (25.0 / array + 20) * 4
+}
+
+println(res.ndArray)
+// [[  250.6449,  428.5840], 
+//  [  269.7913,  202.2077]]
+```
+
+
+Contributed by [Iaroslav Postovalov](https://github.com/CommanderTvis).

kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/INDArrayStructures.kt

@@ -15,7 +15,7 @@ interface INDArrayStructure<T> : NDStructure<T> {
 }
 
 data class INDArrayIntStructure(override val ndArray: INDArray) : INDArrayStructure<Int>, MutableNDStructure<Int> {
-    override fun elementsIterator(): Iterator<Pair<IntArray, Int>> = INDArrayIntIterator(ndArray)
+    override fun elementsIterator(): Iterator<Pair<IntArray, Int>> = ndArray.intIterator()
     override fun get(index: IntArray): Int = ndArray.getInt(*index)
     override fun set(index: IntArray, value: Int): Unit = run { ndArray.putScalar(index, value) }
 }
@@ -23,7 +23,7 @@ data class INDArrayIntStructure(override val ndArray: INDArray) : INDArrayStruct
 fun INDArray.asIntStructure(): INDArrayIntStructure = INDArrayIntStructure(this)
 
 data class INDArrayLongStructure(override val ndArray: INDArray) : INDArrayStructure<Long> {
-    override fun elementsIterator(): Iterator<Pair<IntArray, Long>> = INDArrayLongIterator(ndArray)
+    override fun elementsIterator(): Iterator<Pair<IntArray, Long>> = ndArray.longIterator()
     override fun get(index: IntArray): Long = ndArray.getLong(*index.toLongArray())
 }
 
@@ -31,7 +31,7 @@ fun INDArray.asLongStructure(): INDArrayLongStructure = INDArrayLongStructure(th
 
 data class INDArrayRealStructure(override val ndArray: INDArray) : INDArrayStructure<Double>,
     MutableNDStructure<Double> {
-    override fun elementsIterator(): Iterator<Pair<IntArray, Double>> = INDArrayRealIterator(ndArray)
+    override fun elementsIterator(): Iterator<Pair<IntArray, Double>> = ndArray.realIterator()
     override fun get(index: IntArray): Double = ndArray.getDouble(*index)
     override fun set(index: IntArray, value: Double): Unit = run { ndArray.putScalar(index, value) }
 }
@@ -40,7 +40,7 @@ fun INDArray.asRealStructure(): INDArrayRealStructure = INDArrayRealStructure(th
 
 data class INDArrayFloatStructure(override val ndArray: INDArray) : INDArrayStructure<Float>,
     MutableNDStructure<Float> {
-    override fun elementsIterator(): Iterator<Pair<IntArray, Float>> = INDArrayFloatIterator(ndArray)
+    override fun elementsIterator(): Iterator<Pair<IntArray, Float>> = ndArray.floatIterator()
     override fun get(index: IntArray): Float = ndArray.getFloat(*index)
     override fun set(index: IntArray, value: Float): Unit = run { ndArray.putScalar(index, value) }
 }