Fix gradients calculation for min and max (#48)

tensorflow-ops/src/TensorFlow/Gradient.hs

@@ -459,9 +459,10 @@ opGrad "Max" _ [toT -> x, toT -> indices] [dz] =
   where
     sx = shape (x :: Tensor Value a)
     outputShapeKeptDims = reducedShape sx (indices :: Tensor Value Int32)
-    x' = reshape x outputShapeKeptDims
+    y = CoreOps.max x indices
+    y' = reshape y outputShapeKeptDims
     dz' = reshape dz outputShapeKeptDims
-    indicators = CoreOps.cast $ CoreOps.equal x' x
+    indicators = CoreOps.cast $ CoreOps.equal y' x
     numSelected = reshape (sum indicators indices) outputShapeKeptDims
 
 -- Min and Max have identical gradient implementations.

tensorflow-ops/tensorflow-ops.cabal

@@ -144,10 +144,12 @@ Test-Suite GradientTest
                , lens-family
                , google-shim
                , tensorflow
+               , tensorflow-core-ops
                , tensorflow-ops
                , tensorflow-proto
                , test-framework
                , test-framework-hunit
+               , vector
 
 Test-Suite MiscTest
   default-language: Haskell2010

tensorflow-ops/tests/GradientTest.hs

@@ -15,6 +15,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 
+import Data.Int (Int32)
 import Data.List (sort)
 import Data.ProtoLens.TextFormat (showMessage)
 import Google.Test (googleTest)
@@ -22,14 +23,12 @@ import Lens.Family2 ((^..))
 import Test.Framework (Test)
 import Test.Framework.Providers.HUnit (testCase)
 import Test.HUnit ((@=?))
+import qualified Data.Vector as V
 
-import qualified TensorFlow.Build as TF
+import qualified TensorFlow.Core as TF
+import qualified TensorFlow.GenOps.Core as TF (max)
 import qualified TensorFlow.Gradient as TF
-import qualified TensorFlow.Nodes as TF
 import qualified TensorFlow.Ops as TF
-import qualified TensorFlow.Session as TF
-import qualified TensorFlow.Tensor as TF
-import qualified TensorFlow.Types as TF
 
 import Proto.Tensorflow.Core.Framework.Graph (node)
 import Proto.Tensorflow.Core.Framework.NodeDef (op)
@@ -149,10 +148,20 @@ testDiamond = testCase "testDiamond" $ do
     (4 :: Float) @=? TF.unScalar dx
 
 
+testMaxGradient :: Test
+testMaxGradient = testCase "testMaxGradient" $ do
+    [dx] <- TF.runSession $ TF.buildAnd TF.run $ do
+        let x = TF.vector [1, 2, 3, 0, 1 :: Float]
+            y = TF.max x (0 :: TF.Tensor TF.Value Int32)
+        TF.gradients y [x]
+    V.fromList [0, 0, 1, 0, 0 :: Float] @=? dx
+
+
 main :: IO ()
 main = googleTest [ testGradientSimple
                   , testGradientDisconnected
                   , testCreateGraphStateful
                   , testCreateGraphNameScopes
                   , testDiamond
+                  , testMaxGradient
                   ]