feat(third_party/bazel): Check in rules_haskell from Tweag r/17

1 files changed, 21 insertions, 0 deletions

diff --git a/third_party/bazel/rules_haskell/examples/vector/benchmarks/Algo/Spectral.hs b/third_party/bazel/rules_haskell/examples/vector/benchmarks/Algo/Spectral.hs
new file mode 100644
index 000000000000..811c58269e84
--- /dev/null
+++ b/third_party/bazel/rules_haskell/examples/vector/benchmarks/Algo/Spectral.hs
@@ -0,0 +1,21 @@
+module Algo.Spectral ( spectral ) where
+
+import Data.Vector.Unboxed as V
+
+import Data.Bits
+
+spectral :: Vector Double -> Vector Double
+{-# NOINLINE spectral #-}
+spectral us = us `seq` V.map row (V.enumFromTo 0 (n-1))
+    where
+      n = V.length us
+
+      row i = i `seq` V.sum (V.imap (\j u -> eval_A i j * u) us)
+
+      eval_A i j = 1 / fromIntegral r
+        where
+          r = u + (i+1)
+          u = t `shiftR` 1
+          t = n * (n+1)
+          n = i+j
+