diff --git a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/Arrays.kt b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/Arrays.kt
index 5d341dd68..3d5062a4f 100644
--- a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/Arrays.kt
+++ b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/Arrays.kt
@@ -1,3 +1,4 @@
 package scientifik.kmath.nd4j
 
-internal fun narrowToIntArray(la: LongArray): IntArray = IntArray(la.size) { la[it].toInt() }
\ No newline at end of file
+internal fun widenToLongArray(ia: IntArray): LongArray = LongArray(ia.size) { ia[it].toLong() }
+internal fun narrowToIntArray(la: LongArray): IntArray = IntArray(la.size) { la[it].toInt() }
diff --git a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/INDArrayScalarsIterator.kt b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/INDArrayScalarsIterator.kt
deleted file mode 100644
index 2c2dc970f..000000000
--- a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/INDArrayScalarsIterator.kt
+++ /dev/null
@@ -1,19 +0,0 @@
-package scientifik.kmath.nd4j
-
-import org.nd4j.linalg.api.ndarray.INDArray
-import org.nd4j.linalg.api.shape.Shape
-
-internal class INDArrayScalarsIterator(private val iterateOver: INDArray) : Iterator<Pair<IntArray, INDArray>> {
-    private var i: Int = 0
-
-    override fun hasNext(): Boolean = i < iterateOver.length()
-
-    override fun next(): Pair<IntArray, INDArray> {
-        val idx = if (iterateOver.ordering() == 'c')
-            Shape.ind2subC(iterateOver, i++.toLong())!!
-        else
-            Shape.ind2sub(iterateOver, i++.toLong())!!
-
-        return narrowToIntArray(idx) to iterateOver.getScalar(*idx)
-    }
-}
diff --git a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/ND4JStructure.kt b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/ND4JStructure.kt
deleted file mode 100644
index 1d0301ff9..000000000
--- a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/ND4JStructure.kt
+++ /dev/null
@@ -1,12 +0,0 @@
-package scientifik.kmath.nd4j
-
-import org.nd4j.linalg.api.ndarray.INDArray
-import scientifik.kmath.structures.NDStructure
-
-data class ND4JStructure<T>(val ndArray: INDArray) : NDStructure<INDArray> {
-    override val shape: IntArray
-        get() = narrowToIntArray(ndArray.shape())
-
-    override fun get(index: IntArray): INDArray = ndArray.getScalar(*index)
-    override fun elements(): Sequence<Pair<IntArray, INDArray>> = Sequence { INDArrayScalarsIterator(ndArray) }
-}
diff --git a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/NDArrayIterators.kt b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/NDArrayIterators.kt
new file mode 100644
index 000000000..426b1ec2d
--- /dev/null
+++ b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/NDArrayIterators.kt
@@ -0,0 +1,37 @@
+package scientifik.kmath.nd4j
+
+import org.nd4j.linalg.api.ndarray.INDArray
+import org.nd4j.linalg.api.shape.Shape
+
+internal sealed class INDArrayIteratorBase<T>(protected val iterateOver: INDArray) : Iterator<Pair<IntArray, T>> {
+    private var i: Int = 0
+
+    override fun hasNext(): Boolean = i < iterateOver.length()
+
+    abstract fun getSingle(indices: LongArray): T
+
+    final override fun next(): Pair<IntArray, T> {
+        val la = if (iterateOver.ordering() == 'c')
+            Shape.ind2subC(iterateOver, i++.toLong())!!
+        else
+            Shape.ind2sub(iterateOver, i++.toLong())!!
+
+        return narrowToIntArray(la) to getSingle(la)
+    }
+}
+
+internal class INDArrayDoubleIterator(iterateOver: INDArray) : INDArrayIteratorBase<Double>(iterateOver) {
+    override fun getSingle(indices: LongArray): Double = iterateOver.getDouble(*indices)
+}
+
+internal class INDArrayLongIterator(iterateOver: INDArray) : INDArrayIteratorBase<Long>(iterateOver) {
+    override fun getSingle(indices: LongArray) = iterateOver.getLong(*indices)
+}
+
+internal class INDArrayIntIterator(iterateOver: INDArray) : INDArrayIteratorBase<Int>(iterateOver) {
+    override fun getSingle(indices: LongArray) = iterateOver.getInt(*narrowToIntArray(indices))
+}
+
+internal class INDArrayFloatIterator(iterateOver: INDArray) : INDArrayIteratorBase<Float>(iterateOver) {
+    override fun getSingle(indices: LongArray) = iterateOver.getFloat(*indices)
+}
diff --git a/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/ScalarsND4JStructure.kt b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/ScalarsND4JStructure.kt
new file mode 100644
index 000000000..ef8c3ec2e
--- /dev/null
+++ b/kmath-nd4j/src/main/kotlin/scientifik.kmath.nd4j/ScalarsND4JStructure.kt
@@ -0,0 +1,34 @@
+package scientifik.kmath.nd4j
+
+import org.nd4j.linalg.api.ndarray.INDArray
+import scientifik.kmath.structures.NDStructure
+
+interface INDArrayStructureBase<T> : NDStructure<T> {
+    val ndArray: INDArray
+
+    override val shape: IntArray
+        get() = narrowToIntArray(ndArray.shape())
+
+    fun elementsIterator(): Iterator<Pair<IntArray, T>>
+    override fun elements(): Sequence<Pair<IntArray, T>> = Sequence { elementsIterator() }
+}
+
+data class INDArrayIntStructure(override val ndArray: INDArray) : INDArrayStructureBase<Int> {
+    override fun elementsIterator(): Iterator<Pair<IntArray, Int>> = INDArrayIntIterator(ndArray)
+    override fun get(index: IntArray): Int = ndArray.getInt(*index)
+}
+
+data class INDArrayLongStructure(override val ndArray: INDArray) : INDArrayStructureBase<Long> {
+    override fun elementsIterator(): Iterator<Pair<IntArray, Long>> = INDArrayLongIterator(ndArray)
+    override fun get(index: IntArray): Long = ndArray.getLong(*widenToLongArray(index))
+}
+
+data class INDArrayDoubleStructure(override val ndArray: INDArray) : INDArrayStructureBase<Double> {
+    override fun elementsIterator(): Iterator<Pair<IntArray, Double>> = INDArrayDoubleIterator(ndArray)
+    override fun get(index: IntArray): Double = ndArray.getDouble(*index)
+}
+
+data class INDArrayFloatStructure(override val ndArray: INDArray) : INDArrayStructureBase<Float> {
+    override fun elementsIterator(): Iterator<Pair<IntArray, Float>> = INDArrayFloatIterator(ndArray)
+    override fun get(index: IntArray): Float = ndArray.getFloat(*index)
+}