diff --git a/library/PrimitiveExtras/IO.hs b/library/PrimitiveExtras/IO.hs
--- a/library/PrimitiveExtras/IO.hs
+++ b/library/PrimitiveExtras/IO.hs
@@ -67,3 +67,43 @@
             loop (succ index)
           else unsafeFreezePrimArray array
       in loop 0
+
+traversePrimArrayWithIndexInRange :: Prim a => PrimArray a -> Int -> Int -> (Int -> a -> IO ()) -> IO ()
+traversePrimArrayWithIndexInRange primArray from to action =
+  let iterate index = if index < to
+        then do
+          action index $! indexPrimArray primArray index
+          iterate (succ index)
+        else return ()
+      in iterate from
+
+traversePrimArrayWithIndexConcurrently ::
+  Prim a =>
+  PrimArray a ->
+  Int ->
+  (Int -> a -> IO ()) ->
+  IO (IO ()) {-^ An action, which blocks until the concurrent computation is finished. -}
+traversePrimArrayWithIndexConcurrently primArray threadsAmount action =
+  let size = sizeofPrimArray primArray
+      maxIndex = pred size
+      step = div size threadsAmount
+      in case step of
+        0 -> itraversePrimArray_ action primArray $> return ()
+        _ -> do
+          semaphore <- newTVarIO threadsAmount
+          let
+            startThreads index = if index >= size
+              then return ()
+              else let
+                !nextIndex = step + index
+                in do
+                  forkIO $ do
+                    traversePrimArrayWithIndexInRange primArray index (min nextIndex size) action
+                    atomically (modifyTVar' semaphore pred)
+                  startThreads nextIndex
+            in do
+              startThreads 0
+              return $ atomically $ do
+                activeThreads <- readTVar semaphore
+                guard (activeThreads == 0)
+
diff --git a/library/PrimitiveExtras/Prelude.hs b/library/PrimitiveExtras/Prelude.hs
--- a/library/PrimitiveExtras/Prelude.hs
+++ b/library/PrimitiveExtras/Prelude.hs
@@ -2,6 +2,7 @@
 (
   module Exports,
   Product2(..),
+  modifyTVar',
   forMToZero_,
   forMFromZero_,
 )
@@ -93,6 +94,12 @@
 
 
 data Product2 a b = Product2 !a !b
+
+{-# INLINE modifyTVar' #-}
+modifyTVar' :: TVar a -> (a -> a) -> STM ()
+modifyTVar' var f = do
+    x <- readTVar var
+    writeTVar var $! f x
 
 {-# INLINE forMToZero_ #-}
 forMToZero_ :: Applicative m => Int -> (Int -> m a) -> m ()
diff --git a/primitive-extras.cabal b/primitive-extras.cabal
--- a/primitive-extras.cabal
+++ b/primitive-extras.cabal
@@ -1,7 +1,7 @@
 name:
   primitive-extras
 version:
-  0.1.4
+  0.1.5
 category:
   Primitive
 synopsis: