Browse thread
References, compact bollean values (and other questions)
- Seth J. Fogarty
[
Home
]
[ Index:
by date
|
by threads
]
[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: | 2005-11-03 (23:34) |
From: | Seth J. Fogarty <sfogarty@g...> |
Subject: | References, compact bollean values (and other questions) |
So I am implementing a DPLL procedure for CNF sat. This is the first time, for me, that I've been programming in ocaml that speed is absolutely critical. I will have a small code base running for literally days on end. Thus I have some speed/efficiently questions. First question: I notice references are implemented using mutable records. Does this imply tuples of references are slower than mutable records? I.E. type a = int ref * int ref * int ref vs type a = {mutable a : int; mutable b : int; mutable c : int} Second: I need a non-varient data type. It needs to store three integers and six mutable boolean. I would like this to be done as compactly as possible, ideally in 128 contiguious bits. Will either records or tuples store these contiguously? If I use tuples and references, will ocamlc 'compact' booleans, or give them 32 bits each? I think this is highly unlikely. If I use records, will ocamlc 'compact' booleans, or give them 32 bits each? If I use an integer to represent all six booleans, is there an easy way to gain access to/flip a single bit? I can only find shifting operations in pervasives Third question: How aggressive/intelligent is the ocamlc inlining? Should I worry about inlining functions that I expect to be used millions of times? Fourth question: If you got this far and still want to help, is there anything obviously wrong with the following imperitive linked list implementation in terms of speed? I expect traversal to be rare. I have defined add, delete, and insert operations (that are easily undoable). type 'a ll = Nul | Node of 'a * 'a ll ref | Head of 'a ll ref type 'a llptr = 'a ll * 'a ll (*the predecessor and the node pointed to.*) type 'a undo = 'a ll ref * 'a ll let undo ((a, b) : 'a undo) = a := b let delete (llptr : 'a llptr) : 'a undo = match llptr with |(Head b, (Node (_, b') as deleted)) |(Node (_, b), (Node (_, b') as deleted)) -> b := !b'; (b, deleted) |_ -> failwith "delete" -- Seth Fogarty sfogarty@[gmail.com|rice.edu|livejournal] Neep-neep at large AIM: Sorrath "I know there are people in this world who do not love their fellow human beings - and I hate people like that" --Tom Lehrer.