Fix TensorData encode and decode for Bool (#49)

tensorflow-ops/tensorflow-ops.cabal

@@ -197,6 +197,7 @@ Test-Suite TypesTest
                , lens-family
                , google-shim
                , tensorflow
+               , tensorflow-core-ops
                , tensorflow-ops
                , tensorflow-proto
                , transformers

tensorflow-ops/tests/TypesTest.hs

@@ -37,6 +37,7 @@ import qualified Data.ByteString.Char8 as B8
 import qualified Data.Vector as V
 
 import qualified TensorFlow.ControlFlow as TF
+import qualified TensorFlow.GenOps.Core as TF (select)
 import qualified TensorFlow.Ops as TF
 import qualified TensorFlow.Session as TF
 import qualified TensorFlow.Tensor as TF
@@ -52,17 +53,22 @@ testFFIRoundTrip = testCase "testFFIRoundTrip" $
     TF.runSession $ do
         let floatData = V.fromList [1..6 :: Float]
             stringData = V.fromList [B8.pack (show x) | x <- [1..6::Integer]]
+            boolData = V.fromList [True, True, False, True, False, False]
         f <- TF.build $ TF.placeholder [2,3]
         s <- TF.build $ TF.placeholder [2,3]
+        b <- TF.build $ TF.placeholder [2,3]
         let feeds = [ TF.feed f (TF.encodeTensorData [2,3] floatData)
                     , TF.feed s (TF.encodeTensorData [2,3] stringData)
+                    , TF.feed b (TF.encodeTensorData [2,3] boolData)
                     ]
-        -- It is an error to fetch a tensor that is being fed, so the tensors
-        -- are passed through identity.
-        (f', s') <- TF.runWithFeeds feeds (TF.identity f, TF.identity s)
+        -- Do something idempotent to the tensors to verify that tensorflow can
+        -- handle the encoding. Originally this used `TF.identity`, but that
+        -- wasn't enough to catch a bug in the encoding of Bool.
+        (f', s', b') <- TF.runWithFeeds feeds (f+0, TF.identity s, TF.select b b b)
         liftIO $ do
             floatData @=? f'
             stringData @=? s'
+            boolData @=? b'
 
 
 data TensorDataInputs a = TensorDataInputs [Int64] (V.Vector a)

tensorflow/src/TensorFlow/Types.hs

@@ -241,13 +241,18 @@ instance TensorType ByteString where
         -- Convert to Vector Word8.
         byteVector = S.fromList $ L.unpack $ Builder.toLazyByteString bytes
 
-
+-- TODO: Haskell and tensorflow use different byte sizes for bools, which makes
+-- encoding more expensive. It may make sense to define a custom boolean type.
 instance TensorType Bool where
     tensorType _ = DT_BOOL
     tensorRefType _ = DT_BOOL_REF
     tensorVal = boolVal
-    decodeTensorData = simpleDecode
-    encodeTensorData = simpleEncode
+    decodeTensorData =
+        S.convert . S.map (/= 0) . FFI.tensorDataBytes . unTensorData
+    encodeTensorData (Shape xs) =
+        TensorData . FFI.TensorData xs DT_BOOL . S.map fromBool . S.convert
+      where
+        fromBool x = if x then 1 else 0 :: Word8
 
 instance TensorType (Complex Float) where
     tensorType _ = DT_COMPLEX64