Add Backend docs, additional tests.

Author: dmjio

src/ArrayFire/Backend.hs

@@ -14,24 +14,33 @@ import ArrayFire.FFI
 import ArrayFire.Internal.Backend
 import ArrayFire.Types
 
-setBackend :: Backend -> IO ()
+-- | Set specific 'Backend' to use
+setBackend
+  :: Backend
+  -- ^ 'Backend' to use for 'Array' construction
+  -> IO ()
 setBackend = afCall . af_set_backend . toAFBackend
 
+-- | Retrieve count of Backends available
 getBackendCount :: IO Int
 getBackendCount =
   fromIntegral <$>
     afCall1 af_get_backend_count
 
+-- | Retrieve available 'Backend's
 getAvailableBackends :: IO [Backend]
 getAvailableBackends =
   toBackends . fromIntegral <$>
     afCall1 af_get_available_backends
 
-getBackendID :: Array a -> Backend
-getBackendID = toBackend . flip infoFromArray af_get_backend_id
+-- | Retrieve 'Backend' that specific 'Array' was created from
+getBackend :: Array a -> Backend
+getBackend = toBackend . flip infoFromArray af_get_backend_id
 
+-- | Retrieve active 'Backend'
 getActiveBackend :: IO Backend
 getActiveBackend = toBackend <$> afCall1 af_get_active_backend
 
+-- | Retrieve Device ID that 'Array' was created from
 getDeviceID :: Array a -> Int
 getDeviceID = fromIntegral . flip infoFromArray af_get_device_id

src/ArrayFire/Vision.hs

@@ -26,14 +26,26 @@ import ArrayFire.Internal.Features
 import ArrayFire.Internal.Vision
 import ArrayFire.Types
 
+-- | FAST feature detectors
+--
+-- A circle of radius 3 pixels, translating into a total of 16 pixels, is checked for sequential segments of pixels much brighter or much darker than the central one.
+-- For a pixel p to be considered a feature, there must exist a sequential segment of arc_length pixels in the circle around it such that all are greather than (p + thr) or smaller than (p - thr).
+-- After all features in the image are detected, if nonmax is true, the non-maximal suppression is applied, checking all detected features and the features detected in its 8-neighborhood and discard it if its score is non maximal.
 fast
   :: Array a
+  -- ^ Array containing a grayscale image (color images are not supported)
   -> Float
+  -- ^ FAST threshold for which a pixel of the circle around the central pixel is considered to be greater or smaller
   -> Int
+  -- ^ Length of arc (or sequential segment) to be tested, must be within range [9-16]
   -> Bool
+  -- ^ Performs non-maximal suppression if true
   -> Float
+  -- ^ Maximum ratio of features to detect, the maximum number of features is calculated by feature_ratio * in.elements(). The maximum number of features is not based on the score, instead, features detected after the limit is reached are discarded
   -> Int
+  -- ^ Is the length of the edges in the image to be discarded by FAST (minimum is 3, as the radius of the circle)
   -> Features
+  -- ^ Struct containing arrays for x and y coordinates and score, while array orientation is set to 0 as FAST does not compute orientation, and size is set to 1 as FAST does not compute multiple scales
 fast (Array fptr) thr (fromIntegral -> arc) (fromIntegral . fromEnum -> non) ratio (fromIntegral -> edge)
   = unsafePerformIO . mask_ . withForeignPtr fptr $ \aptr ->
       do feat <- alloca $ \ptr -> do

test/ArrayFire/BackendSpec.hs

@@ -18,4 +18,4 @@ spec =
       setBackend backend
       (`shouldBe` backend) =<< getActiveBackend
       let arr = matrix @Int (2,2) [1..]
-      getBackendID arr `shouldBe` backend
+      getBackend arr `shouldBe` backend

test/ArrayFire/LAPACKSpec.hs

@@ -30,7 +30,10 @@ spec =
       A.getDims s `shouldBe` (3,3,1,1)
       A.getDims v `shouldBe` (3,3,1,1)
       A.getDims d `shouldBe` (3,1,1,1)
-    it "Should get determinant" $ do
+    it "Should get determinant of Double" $ do
+      let eles = [3 A.:+ 1, 8 A.:+ 1, 4 A.:+ 1, 6 A.:+ 1]
+          (x,y) = A.det (A.matrix @(A.Complex Double) (2,2) eles)
+      x `shouldBe` (-14)
       let (x,y) = A.det $ A.matrix @Double (2,2) [3,8,4,6]
       x `shouldBe` (-14)
     it "Should calculate inverse" $ do

test/ArrayFire/VisionSpec.hs

@@ -7,5 +7,8 @@ import           Test.Hspec
 spec :: Spec
 spec =
   describe "Vision spec" $ do
-    it "Should get difference of gaussians" $ do
+    it "Should construct Features for fast feature detection" $ do
+      let arr = A.vector @Int 30000 [1..]
+      let feats = A.fast arr 1.0 9 False 1.0 3
       (1 + 1) `shouldBe` 2
+