Path: utzoo!attcan!uunet!mcsun!ub4b!kulcs!alain
From: alain@kulcs.uucp (Alain Callebaut)
Newsgroups: comp.lang.prolog
Subject: Re: Why is bagof so slow?
Message-ID: <1974@kulcs.kulcs.uucp>
Date: 28 May 90 08:12:13 GMT
Reply-To: alain@kulcs.UUCP ()
Organization: Katholieke Universiteit Leuven, Dept. Computer Science
Lines: 20


In article <2556@randvax.UUCP> Sanjai Narain writes : 

> In the following program, there is one fact about f, namely f(1). 
> Running times of two queries, each run a thousand times, are compared:
> 
> 	f(X).
> 	bagof(X,f(X),S). 
> 
> The first takes about 25ms, whereas the second about 1200ms. Why a
> 40-fold difference in speed? Are there ways to speed up computation 
> of sets? Timings are for Quintus Prolog on a SPARC station, running
> UNIX, with 16mb of main memory.

If you don't need the full flexibility of bagof, you could use findall 
instead : that's much faster.  I did the same timings, on a SPARCstation 1, 
with 16 MB, for BIM_Prolog 2.5.  The f(X) took 10ms, the bagof 330ms and 
a findall 150ms. 

Alain Callebaut