added files for fine-grained linked list as a set#79
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| match temp with | ||
| | Some _ when temp == cur && prev == verify -> insert prev | ||
| | None when cur = None && prev == verify -> insert prev | ||
| | _ -> |
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You could also use a simple conditional
if prev == verify && cur == verify.next then
insert prev
else
...here. This will also be slightly faster, because there is no need to distinguish between Some _ and None.
| let add t value = | ||
| (* x will point to the new node after insertion *) | ||
| let insert x = | ||
| if x.value = value && not (x == t.head) then ( |
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It is usually best to give the notion of equality over values as a parameter, i.e. there should be something like t.eq x.value value here.
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Actually you want t.compare x.value value = 0, because the values need to be ordered.
| | Some node -> node | ||
| | _ -> | ||
| is_tail := true; | ||
| create_node value None |
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Hmm... Is the node created here used for something?
| is_tail := true; | ||
| create_node value None | ||
| in | ||
| if !is_tail then ( |
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Could you avoid allocating a ref cell for the is_tail condition by inlining the continuation branches to the match:
match cur with
| None ->
Mutex.unlock prev.lock;
false
| Some to_find ->
Mutex.lock to_find.lock;
let verify = find_previous_remove t value in
(* ... *)
| let temp = verify.next in | ||
| match temp with | ||
| | Some _ when temp == cur && prev == verify -> | ||
| let res = to_find.value = value in |
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I believe the logic around here could be simplified and the equality check can be moved outside of the critical section. Something like this:
let verify = find_previous_remove t value in
if prev == verify && cur == verify.next then begin
Mutex.unlock prev.lock;
Mutex.unlock to_find.lock;
to_find.value = value (* better to use user defined equality *)
end
else begin
Mutex.unlock prev.lock;
Mutex.unlock to_find.lock;
let again = find_previous_remove t value in
validate again again.next
endThe common prefix of both branches could also be factored out.
| let find_previous_add t key = | ||
| let rec aux prev next = | ||
| match next with | ||
| | Some node when node.value > key -> prev |
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Hmm... I wonder whether the logic and add and remove could be modified slightly so that only a single find_previous helper would be needed without impacting performance.
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Implementation of a Fine-grained linked list (as a set) based on optimistic synchronisation referred from section 9.6 in art of multiprocessor programming. The add function requires only 1 lock, and the remove function requires 2 locks. The linked list works like a set, with elements arranged in ascending order.