From 835d64d797411141a1b21948566651d6dace882e Mon Sep 17 00:00:00 2001
From: Roland Grinis <roland.grinis@grinisrit.com>
Date: Sat, 16 Jan 2021 19:29:47 +0000
Subject: [PATCH] Initial draft for TensorAlgebra

---
 .gitignore                                    |  1 +
 .../kmath/structures/TensorAlgebra.kt         | 49 +++++++++++++++++++
 .../kmath/structures/TensorStructure.kt       | 11 +++++
 3 files changed, 61 insertions(+)
 create mode 100644 kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorAlgebra.kt
 create mode 100644 kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorStructure.kt

diff --git a/.gitignore b/.gitignore
index bade7f08c..ea8e65fb4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 build/
 out/
 .idea/
+.vscode/
 
 # Avoid ignoring Gradle wrapper jar file (.jar files are usually ignored)
 !gradle-wrapper.jar
diff --git a/kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorAlgebra.kt b/kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorAlgebra.kt
new file mode 100644
index 000000000..f960742ee
--- /dev/null
+++ b/kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorAlgebra.kt
@@ -0,0 +1,49 @@
+package kscience.kmath.structures
+
+
+import kscience.kmath.operations.*
+
+public interface TensorAlgebra<T, TorchTensorType : TensorStructure<T>> : Ring<TorchTensorType> {
+
+    public operator fun T.plus(other: TorchTensorType): TorchTensorType
+    public operator fun TorchTensorType.plus(value: T): TorchTensorType
+    public operator fun TorchTensorType.plusAssign(value: T): Unit
+    public operator fun TorchTensorType.plusAssign(b: TorchTensorType): Unit
+
+    public operator fun T.minus(other: TorchTensorType): TorchTensorType
+    public operator fun TorchTensorType.minus(value: T): TorchTensorType
+    public operator fun TorchTensorType.minusAssign(value: T): Unit
+    public operator fun TorchTensorType.minusAssign(b: TorchTensorType): Unit
+
+    public operator fun T.times(other: TorchTensorType): TorchTensorType
+    public operator fun TorchTensorType.times(value: T): TorchTensorType
+    public operator fun TorchTensorType.timesAssign(value: T): Unit
+    public operator fun TorchTensorType.timesAssign(b: TorchTensorType): Unit
+
+    public infix fun TorchTensorType.dot(b: TorchTensorType): TorchTensorType
+
+    public fun diagonalEmbedding(
+        diagonalEntries: TorchTensorType,
+        offset: Int = 0, dim1: Int = -2, dim2: Int = -1
+    ): TorchTensorType
+
+    public fun TorchTensorType.transpose(i: Int, j: Int): TorchTensorType
+    public fun TorchTensorType.view(shape: IntArray): TorchTensorType
+
+    public fun TorchTensorType.abs(): TorchTensorType
+    public fun TorchTensorType.sum(): TorchTensorType
+
+}
+
+public interface TensorFieldAlgebra<T, TorchTensorType : TensorStructure<T>> :
+    TensorAlgebra<T, TorchTensorType>, Field<TorchTensorType> {
+
+    public operator fun TorchTensorType.divAssign(b: TorchTensorType)
+
+    public fun TorchTensorType.exp(): TorchTensorType
+    public fun TorchTensorType.log(): TorchTensorType
+
+    public fun TorchTensorType.svd(): Triple<TorchTensorType, TorchTensorType, TorchTensorType>
+    public fun TorchTensorType.symEig(eigenvectors: Boolean = true): Pair<TorchTensorType, TorchTensorType>
+
+}
\ No newline at end of file
diff --git a/kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorStructure.kt b/kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorStructure.kt
new file mode 100644
index 000000000..6e3ac0b7b
--- /dev/null
+++ b/kmath-core/src/commonMain/kotlin/kscience/kmath/structures/TensorStructure.kt
@@ -0,0 +1,11 @@
+package kscience.kmath.structures
+
+public abstract class TensorStructure<T>: MutableNDStructure<T> {
+
+    // A tensor can have empty shape, in which case it represents just a value
+    public abstract fun value(): T
+
+    // Tensors are mutable and might hold shared resources
+    override fun equals(other: Any?): Boolean = false
+    override fun hashCode(): Int = 0
+}
\ No newline at end of file