Merge pull request #30 from ThoughtWorksInc/transformed-views

Implement some transformed views

Tensors/src/main/scala/com/thoughtworks/compute/Tensors.scala

@@ -163,7 +163,63 @@ trait Tensors extends OpenCL {
       }
     }
 
-    def split(dimension: Int): Seq[Tensor] = ???
+    def permute(dimensions: Array[Int]): TransformedTensor = {
+      val length = shape.length
+      if (dimensions.length != length) {
+        throw new IllegalArgumentException
+      }
+      val newShape = Array.ofDim[Int](length)
+      val matrix = Array.ofDim[Double](length * (length + 1))
+      @tailrec def loop(newDimensionIndex: Int): Unit = {
+        if (newDimensionIndex < length) {
+          val oldDimensionIndex = dimensions(newDimensionIndex)
+          newShape(newDimensionIndex) = shape(oldDimensionIndex)
+          matrix(oldDimensionIndex * (length + 1) + newDimensionIndex) = 1.0
+          loop(newDimensionIndex + 1)
+        }
+      }
+      loop(0)
+      transform(newShape, matrix)
+    }
+
+    def split(dimension: Int): IndexedSeq[Tensor] = {
+      // TODO: override map/reduce to produce less OpenCL C code
+      new IndexedSeq[Tensor] {
+
+        private val newShape = shape.patch(dimension, Nil, 1)
+
+        val length: Int = shape(dimension)
+
+        def apply(index: Int): TransformedTensor = {
+          val length = shape.length
+          val matrix = Array.ofDim[Double](length * length)
+
+          @tailrec
+          def loopBefore(i: Int): Unit = {
+            if (i < dimension) {
+              matrix(i * length + i) = 1.0
+              loopBefore(i + 1)
+            }
+          }
+          loopBefore(0)
+
+          matrix(dimension * length + length - 1) = index.toDouble
+
+          @tailrec
+          def loopAfter(i: Int): Unit = {
+            if (i < length) {
+              matrix(i * length + i - 1) = 1.0
+              loopAfter(i + 1)
+            }
+          }
+          loopAfter(dimension + 1)
+
+          // TODO: Cache the transformed tensor
+          transform(newShape, matrix)
+        }
+
+      }
+    }
 
     //    def debuggingInformation: Implicitly[DebuggingInformation]