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Simplify mkCacheInt32/mkCacheGeneric to use ConcurrentDictionary #486

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Merged
sergey-tihon merged 2 commits into from
Mar 22, 2026
Merged

Simplify mkCacheInt32/mkCacheGeneric to use ConcurrentDictionary #486

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Initial plan
Copilot Mar 22, 2026
06cc89a
Simplify mkCacheInt32/mkCacheGeneric using ConcurrentDictionary
Copilot Mar 22, 2026
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32 changes: 14 additions & 18 deletions src/ProvidedTypes.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -4586,29 +4586,25 @@ module internal AssemblyReader =

let mkCacheInt32 lowMem _infile _nm _sz =
if lowMem then (fun f x -> f x) else
let cache = Dictionary<int32, _>()
let syncObj = obj()
let cache = ConcurrentDictionary<int32, _>()
fun f (idx:int32) ->
lock syncObj (fun () ->
let mutable res = Unchecked.defaultof<_>
if cache.TryGetValue(idx, &res) then res
else
let v = f idx
cache.[idx] <- v
v)
match cache.TryGetValue idx with
| true, v -> v
| false, _ ->
let v = f idx
cache.TryAdd(idx, v) |> ignore
cache.[idx]
Comment on lines +4589 to +4596
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Copilot AI Mar 22, 2026

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cache.TryGetValue idx uses the F# out-arg-to-tuple translation, which allocates a tuple on every cache access (including hits). Since this cache is likely hot, consider using the byref overload (let mutable res = Unchecked.defaultof<_>; if cache.TryGetValue(idx, &res) then res else ...) to avoid per-call allocations. Also, after TryAdd you can return v directly when the add succeeds to avoid a second dictionary lookup.

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let mkCacheGeneric lowMem _inbase _nm _sz =
if lowMem then (fun f x -> f x) else
let cache = Dictionary<'T, _>()
let syncObj = obj()
let cache = ConcurrentDictionary<'T, _>()
fun f (idx :'T) ->
lock syncObj (fun () ->
match cache.TryGetValue idx with
| true, cached -> cached
| false, _ ->
let v = f idx
cache.[idx] <- v
v)
match cache.TryGetValue idx with
| true, v -> v
| false, _ ->
let v = f idx
cache.TryAdd(idx, v) |> ignore
cache.[idx]
Comment on lines +4602 to +4607
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Copilot AI Mar 22, 2026

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After computing v on a miss, the code does TryAdd and then unconditionally reads cache.[idx], which forces another lookup. Consider returning v when TryAdd succeeds (and only falling back to reading from the dictionary when it fails due to a concurrent add). This keeps the concurrent behavior but avoids extra work on every miss.

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let seekFindRow numRows rowChooser =
let mutable i = 1
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