Reduce allocations in some Array.Parallel funcs

Author: brianrourkeboll

src/FSharp.Core/array.fs

@@ -2179,9 +2179,8 @@ module Array =
             // Not exists $condition <==> (opposite of $condition is true forall)
             exists (predicate >> not) array |> not
 
-        [<CompiledName("TryFindIndex")>]
-        let tryFindIndex predicate (array: _ array) =
-            checkNonNull "array" array
+        let inline tryFindIndexAux predicate (array: _ array) =
+            checkNonNull (nameof array) array
 
             let pResult =
                 Parallel.For(
@@ -2192,32 +2191,38 @@ module Array =
                             pState.Break())
                 )
 
-            pResult.LowestBreakIteration |> Option.ofNullable |> Option.map int
+            pResult.LowestBreakIteration
+
+        [<CompiledName("TryFindIndex")>]
+        let tryFindIndex predicate (array: _ array) =
+            let i = tryFindIndexAux predicate array
+            if i.HasValue then Some (int (i.GetValueOrDefault()))
+            else None
 
         [<CompiledName("TryFind")>]
         let tryFind predicate (array: _ array) =
-            array |> tryFindIndex predicate |> Option.map (fun i -> array[i])
+            let i = tryFindIndexAux predicate array
+            if i.HasValue then Some array[int (i.GetValueOrDefault())]
+            else None
 
         [<CompiledName("TryPick")>]
         let tryPick chooser (array: _ array) =
             checkNonNull "array" array
-            let allChosen = new System.Collections.Concurrent.ConcurrentDictionary<_, _>()
+            let mutable chosen = None
 
-            let pResult =
+            let _pResult =
                 Parallel.For(
                     0,
                     array.Length,
                     (fun i pState ->
                         match chooser array[i] with
                         | None -> ()
                         | chosenElement ->
-                            allChosen[i] <- chosenElement
+                            ignore (Interlocked.Exchange(&chosen, chosenElement))
                             pState.Break())
                 )
 
-            pResult.LowestBreakIteration
-            |> Option.ofNullable
-            |> Option.bind (fun i -> allChosen[int i])
+            chosen
 
         [<CompiledName("Choose")>]
         let choose chooser (array: 'T array) =