1 files changed, 31 insertions, 0 deletions
diff --git a/testsuite/tests/perf/should_run/T5113.hs b/testsuite/tests/perf/should_run/T5113.hs
new file mode 100644
index 0000000000..e87bcb6cad
--- /dev/null
+++ b/testsuite/tests/perf/should_run/T5113.hs
@@ -0,0 +1,31 @@
+{-# LANGUAGE BangPatterns #-}
+module Main where
+
+import Data.Array.Base (unsafeRead, unsafeWrite)
+import Data.Array.ST
+import Data.Array.Unboxed
+import Control.Monad.ST
+
+main = print (divisorCounts 1000000 ! 342)
+
+isqrt :: Int -> Int
+isqrt n = floor (sqrt $ fromIntegral n)
+
+divisorCounts :: Int -> UArray Int Int
+divisorCounts n = runSTUArray $ do
+    let !rt = isqrt n
+    darr <- newArray (0,n) 1 :: ST s (STUArray s Int Int)
+    let inc i = unsafeRead darr i >>= \k -> unsafeWrite darr i (k+1)
+        note step i
+            | i > n     = return ()
+            | otherwise = do
+                inc i
+                note step (i+step)
+        count j
+            | j > rt    = return ()
+            | otherwise = do
+                note (2*j) (j*j)
+                count (j+2)
+    note 2 4
+    count 3
+    return darr