1 files changed, 45 insertions, 0 deletions
diff --git a/third_party/bazel/rules_haskell/examples/vector/benchmarks/TestData/Graph.hs b/third_party/bazel/rules_haskell/examples/vector/benchmarks/TestData/Graph.hs
new file mode 100644
index 0000000000..8b8ca837b8
--- /dev/null
+++ b/third_party/bazel/rules_haskell/examples/vector/benchmarks/TestData/Graph.hs
@@ -0,0 +1,45 @@
+module TestData.Graph ( randomGraph )
+where
+
+import System.Random.MWC
+import qualified Data.Array.ST as STA
+import qualified Data.Vector.Unboxed as V
+
+import Control.Monad.ST ( ST, runST )
+
+randomGraph :: Int -> (Int, V.Vector Int, V.Vector Int)
+randomGraph e
+  = runST (
+    do
+      g <- create
+      arr <- STA.newArray (0,n-1) [] :: ST s (STA.STArray s Int [Int])
+      addRandomEdges n g arr e
+      xs <- STA.getAssocs arr
+      let (as,bs) = unzip [(i,j) | (i,js) <- xs, j <- js ]
+      return (n, V.fromListN (length as) as, V.fromListN (length bs) bs)
+    )
+  where
+    n = e `div` 10
+
+addRandomEdges :: Int -> Gen s -> STA.STArray s Int [Int] -> Int -> ST s ()
+addRandomEdges n g arr = fill
+  where
+    fill 0 = return ()
+    fill e
+      = do
+          m <- random_index
+          n <- random_index
+          let lo = min m n
+              hi = max m n
+          ns <- STA.readArray arr lo
+          if lo == hi || hi `elem` ns
+            then fill e
+            else do
+                   STA.writeArray arr lo (hi:ns)
+                   fill (e-1)
+
+    random_index = do
+                     x <- uniform g
+                     let i = floor ((x::Double) * toEnum n)
+                     if i == n then return 0 else return i
+