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From: dewar@merv.cs.nyu.edu (Robert Dewar)
Subject: Re: GNAT uppgrades slows thing down ???
Date: 1997/03/15
Message-ID: <dewar.858439416@merv>#1/1
X-Deja-AN: 225803183
References: <01bc2f1b$4998bba0$355ff482@default>
Organization: New York University
Newsgroups: comp.lang.ada
Date: 1997-03-15T00:00:00+00:00
List-Id: <comp.lang.ada>


Joakim said

<<I've used GNAT 3.01 for ms-dos on 486sx25 8M and it was mm.. fast,
but I uppgraded to GNAT3.05 for ms-dos, that was a slow compiler.

Then when I upgraded my PC to Pentium 133Mhz 16 M and Win95, I got GNAT
3.04a
wow it was fast.
Now I'm back where I started with a slow compiler when I downloaded GNAT
3.09,
 its slower than GNAT3.05 on my old 486.

What has happend to GNAT will just be slower and slower or????>>

No, in fact the GNAT 3.09 compiler is considerably faster than any previous
version, and future versions will be faster, BUT you have to be careful

to install it right. 

You are using a machine with very small memory (16M is very small for most
software today, and is certainly very small for GNAT, especially if you
are running Win95). 

That means that the performance can very delicately depend on how disk
caches are set up, since you are on edge for memory performance, and
disk thrashing can cause HUGE slow downs if you do not tune things 
right. Given that you can upgrade to 32M for about $80, I think you
would do yourself a big favor by doing so (I would not even want to
try running Might and Magic in 16 megs, let alone GNAT!)

GNAT does get slightly bigger (i.e. the actual exectable of the compiler
gets bigger), and that definitely will be a continuing trend as more
features and optimizations are added. This can cause discontinuities
in performance on memory crunched machines (I very well remember the
effect of outgrowing the 2 meg cache on OS/2, before I discovered the
use of emxload).

One of the services we provide to our customers is advice on appropriate
configurations for GNAT and how to install it and tune things so that
it runs fast. Obviously you are not installed optimally, so you need to
get one of these "inside secrets of Win95" books and fiddle (but I would
first save up your $$ for 16 meg, at least, of extra memory, you will find
it makes everything in a Win95 environment much faster. Even though you
have a fairly slow processor (by todays standards), you will find that it
flies by comparison if it is given enough memory. Right now you are probably
spending all your time waiting on your (slow) disk.

Robert dewar
Ada Core Technologies