It sounds like you don't have any real experience in working with
large datasets (in Stata or otherwise) and have no actual measured
results of different computing platforms in terms of speed, but
instead want to promote some agenda. It may be "rare" for you to work
with very large datasets, but some people do it on a regular basis,
especially those that work with large scale admistrative databases
(e.g., national health programs or, in my case, utility company
databases which I admit only tend to run up to about 1GB).
You are incorrect that you only need 64bit computing if you are going
to use more 4GB of data-- do you know of a 32bit OS/hardware platform
that can allocate 4GB of ram to a process? or even 3GB? There have
been Statalist postings showing about 2GB data area max for Mac OS
10.3 on a G5 and other posts indicating that about 2GB will be the max
for most 32bit OSs. Maybe 32bit Linux can allocate more, but I
haven't heard that. 64bit also provides potential speed improvements,
not just max RAM allocation (see below).
I don't think it makes much sense to start writing your own data
analysis system in C if you already have a developed and tested tool
(like Stata) that does what you want. It is far easier (and cheaper
by an order of magnitude or more) to buy a 64bit platform, load it
with RAM and use Stata than it is to write your own code from
scratch, especially if you want to do many things. Perhaps if you
have one big repeating analysis it may make sense to write some code,
but Stata is actually quite fast even with very large datasets,
especially if you know what you're doing to optimize your Stata code.
While Windows has many shortcomings, your comment that 64bit computing
under Windows is "stupid" does not appear to be backed up by any
actual tests or comparisons. You say that Windows is "inexcusably
slow" but all of the comparisons I've seen posted to Statalist and
elsewhere seem to indicate that, for massive data analysis, the speed
of execution is comparable across equal-bit operating systems.
Comparisons of GAUSS speed on different platforms/OSs at
http://www.scientificweb.com/testreport/gaussbench2.html
doesn't seem to show Windows lagging Linux, results are mixed across
tests. I'd be interested in seeing any actual data you have showing
Win64 being substantially slower at computational tasks than another
OS since I am considering moving to 64bit soon.
There was a Statalist posting that showed moving from 32bit WinXP to
64bit Linux (both with AMD 64bit processors, but different models)
led to 29%-34% speed improvements in calculating some complex gllamm
models. But this difference is between 32bit and 64bit. see:
http://www.stata.com/statalist/archive/2004-04/msg00620.html
Michael Blasnik
[email protected]
----- Original Message ----- From: "James Muller"
<[email protected]>
To: <[email protected]>
Sent: Monday, June 20, 2005 8:31 AM
Subject: Re: st: Addressing > 2 gig of RAM
At the outset, I don't have experience with 64-bit Stata at all, but
I can give you some of my _opinions_ on 64-bit computing:
First, you don't need 64 bit if you're going to use no more than 4Gb.
32 bit is 2^32=4Gb. You only actually need 64 bit if you're actually
going to need more than 4Gb.
Related, second, are you actually going to need to have >4Gb of data
in memory all at the same time? That is a massive amount of data -
Stata's most detailed data type is double, which is 8 bytes. That
means that you would have to _need_ at some moment in time to be
using 2^26=67108864 double objects, which is rare. There is a strong
argument then to store your data in a dedicated database, pulling out
only the data you need when you need it, and dropping it from memory
when it's not needed. And if you did that then Stata is not the best
way to go - again, it's worth looking at c or fortran. There are good
open source libraries for doing lots of fun things in those
languages, and the methods usually aren't too hard to implement
oneself anyway. In my opinion worth it for such large apps.
Third, if you're actually doing 64 bit computing then you're after
some pretty hardcore efficiency. It is worth at least considering
more scientific methods of computing, for example writing custom
programs for your application in c or fortran. Like I say, I don't
have any experience with 64-bit Stata, but I'd suspect that not too
many people would keep using Stata for such large applications.
Fourth, 64-bit computing under Windows is just plain stupid. Sorry
for anybody who disagrees, but Windows is an operating system that is
inexcusably slow and memory-hungry. Again, 64-bit computing is just
that - computing. You're after efficiency so that you're not waiting
the next 5 months for the task to end, and you certainly want
something stable for time-consuming tasks. Learning to use a proper
OS (and using very efficient software in general) is worth it if
you're getting into the heavy stuff. Additionally, as is pointed out
in a post just before this, Stata needs a contiguous block of memory.
Windows does not handle memory well, i.e. you'll not have the whole
set of RAM available. A shame after investing in it, not to be able
to use it...
Fifth, as far as I'm aware (and I may well have my wires crossed
here), current Mac OS's use a variation the Linux kernel, and do so
because they are after efficiency and stability. While the hardware
of G4/similar is excellent, I'd expect Linux to run better than MacOS
on a equivalent hardware.
Sixth, and this definitely depends on the scale of your project, if
you're doing stuff that is slow (i.e. trillions and trillions of
calculations) then it's worth looking into parallel processing. This,
however, steps into the realm of employing a programmer or spending
lots of time studying.
Seventh, if you end up going with 64-bit linux, make sure you have an
efficient system. 'Linux' has a big reputation as being fast and
efficient, but many out-of-the-box distributions pile a bucketload of
features that aren't necessary for a lot of situations. They all eat
up resources and you end up losing a lot of the advantages. Thus, if
you go with something like Fedora Core 64, spend the time giving your
system a good haircut - and look carefully at performance reviews and
comparisons. Also, ask the guys at Stata about whether their 64-bit
Linux Stata will work on the BSDs. BSD is quite nice and should not
be dismissed.
Eigth, if you go with 64-bit and choose a PC for your platform, be
sure to look into Athlon 64bit CPU.
Overall, my opinion is that if somebody's going to spend the cash to
purchase more than 4Gb of RAM and a good 64-bit processor (or
processors) then they should spend the time getting their system to
do justice to that investment. That means really looking into getting
things optimized, which means looking seriously at alternative ways
of approaching the problem.
Righto, my sixteen cents there. Hope it's useful.
James
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