Merge pull request #59 from DiffSharp/arraySlicing

Correction to matrix slicing for start point of AddSubMatrix

Author: cgravill

src/DiffSharp/AD.Float32.fs

@@ -1474,7 +1474,7 @@ and DM =
         match d with
         | DM(ap) -> DM(ap.[rowStart..rowFinish, colStart..colFinish])
         | DMF(ap, at, ai) -> DMF(ap.[rowStart..rowFinish, colStart..colFinish], at.[rowStart..rowFinish, colStart..colFinish], ai)
-        | DMR(ap, _, ai, _) -> let cp = ap.[rowStart..rowFinish, colStart..colFinish] in DM.R(cp, Slice_DM(d, rowStart, rowFinish), ai)
+        | DMR(ap, _, ai, _) -> let cp = ap.[rowStart..rowFinish, colStart..colFinish] in DM.R(cp, Slice_DM(d, rowStart, colStart), ai)
 
     member d.GetSlice(row, colStart, colFinish) =
         let colStart = defaultArg colStart 0

src/DiffSharp/AD.Float64.fs

@@ -1474,7 +1474,7 @@ and DM =
         match d with
         | DM(ap) -> DM(ap.[rowStart..rowFinish, colStart..colFinish])
         | DMF(ap, at, ai) -> DMF(ap.[rowStart..rowFinish, colStart..colFinish], at.[rowStart..rowFinish, colStart..colFinish], ai)
-        | DMR(ap, _, ai, _) -> let cp = ap.[rowStart..rowFinish, colStart..colFinish] in DM.R(cp, Slice_DM(d, rowStart, rowFinish), ai)
+        | DMR(ap, _, ai, _) -> let cp = ap.[rowStart..rowFinish, colStart..colFinish] in DM.R(cp, Slice_DM(d, rowStart, colStart), ai)
 
     member d.GetSlice(row, colStart, colFinish) =
         let colStart = defaultArg colStart 0

tests/DiffSharp.Tests/AD.Float32.fs

@@ -54,4 +54,23 @@ let ``Gradient descent``() =
         let g = (x*Wg)
         cos g.[0,0]
 
-    minimize lossFunction (DV.create 5 1.0f) //Smoke test
+    minimize lossFunction (DV.create 5 1.0f) //Smoke test
+
+
+[<Property>]
+let ``Gradient descent (with arrays)``() =
+
+    let minimize (f:DV->D) (x0:DV) = 
+        let eta = 1e-2f
+        let mutable W = x0
+        for _ in [0..10] do
+            let L,g = grad' f W
+            W <- W - eta*g
+
+    let n = 5
+    let lossFunction (w:DV) =
+        let x = DM.init n n (fun i j -> w.[n*i+j])
+        let x' = x.GetSlice(None, None, None, None)
+        cos x'.[0,0]
+
+    minimize lossFunction (DV.create (n*n) 1.0f) //Smoke test