From f6cc23ce0a92aad58158a40f370d62727fb29f86 Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@gmail.com>
Date: Sun, 10 Feb 2019 09:11:58 +0300
Subject: [PATCH] Optimized Field for DoubleBuffer operations.

---
 .../kmath/structures/RealBufferField.kt       | 59 +++++++++++++++++++
 .../kmath/structures/SpecializedStructures.kt |  6 ++
 2 files changed, 65 insertions(+)
 create mode 100644 kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/RealBufferField.kt

diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/RealBufferField.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/RealBufferField.kt
new file mode 100644
index 000000000..f1df3a0f4
--- /dev/null
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/RealBufferField.kt
@@ -0,0 +1,59 @@
+package scientifik.kmath.structures
+
+import scientifik.kmath.operations.Field
+
+/**
+ * A simple field over linear buffers of [Double]
+ */
+class RealBufferField(val size: Int) : Field<Buffer<Double>> {
+    override val zero: Buffer<Double> = Buffer.DoubleBufferFactory(size) { 0.0 }
+
+    override val one: Buffer<Double> = Buffer.DoubleBufferFactory(size) { 1.0 }
+
+    override fun add(a: Buffer<Double>, b: Buffer<Double>): DoubleBuffer {
+        require(a.size == size) { "The size of buffer is ${a.size} but context requires $size " }
+        require(b.size == size) { "The size of buffer is ${b.size} but context requires $size " }
+        return if (a is DoubleBuffer && b is DoubleBuffer) {
+            val aArray = a.array
+            val bArray = b.array
+            DoubleBuffer(DoubleArray(size) { aArray[it] + bArray[it] })
+        } else {
+            DoubleBuffer(DoubleArray(size) { a[it] + b[it] })
+        }
+    }
+
+    override fun multiply(a: Buffer<Double>, k: Number): DoubleBuffer {
+        require(a.size == size) { "The size of buffer is ${a.size} but context requires $size " }
+        val kValue = k.toDouble()
+        return if (a is DoubleBuffer) {
+            val aArray = a.array
+            DoubleBuffer(DoubleArray(size) { aArray[it] * kValue })
+        } else {
+            DoubleBuffer(DoubleArray(size) { a[it] * kValue })
+        }
+    }
+
+    override fun multiply(a: Buffer<Double>, b: Buffer<Double>): DoubleBuffer {
+        require(a.size == size) { "The size of buffer is ${a.size} but context requires $size " }
+        require(b.size == size) { "The size of buffer is ${b.size} but context requires $size " }
+        return if (a is DoubleBuffer && b is DoubleBuffer) {
+            val aArray = a.array
+            val bArray = b.array
+            DoubleBuffer(DoubleArray(size) { aArray[it] * bArray[it] })
+        } else {
+            DoubleBuffer(DoubleArray(size) { a[it] * b[it] })
+        }
+    }
+
+    override fun divide(a: Buffer<Double>, b: Buffer<Double>): DoubleBuffer {
+        require(a.size == size) { "The size of buffer is ${a.size} but context requires $size " }
+        require(b.size == size) { "The size of buffer is ${b.size} but context requires $size " }
+        return if (a is DoubleBuffer && b is DoubleBuffer) {
+            val aArray = a.array
+            val bArray = b.array
+            DoubleBuffer(DoubleArray(size) { aArray[it] / bArray[it] })
+        } else {
+            DoubleBuffer(DoubleArray(size) { a[it] / b[it] })
+        }
+    }
+}
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt
index b0373288b..734aba5ac 100644
--- a/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt
+++ b/kmath-core/src/commonMain/kotlin/scientifik/kmath/structures/SpecializedStructures.kt
@@ -36,6 +36,12 @@ fun <T> NDStructure<T>.as1D(): Structure1D<T> = if (shape.size == 1) {
     error("Can't create 1d-structure from ${shape.size}d-structure")
 }
 
+fun <T> NDBuffer<T>.as1D(): Structure1D<T> = if (shape.size == 1) {
+    Buffer1DWrapper(this.buffer)
+} else {
+    error("Can't create 1d-structure from ${shape.size}d-structure")
+}
+
 /**
  * A structure wrapper for buffer
  */