Am I the poster-child for needing a Mac Pro?

[firstyearprof]

Hi All,

Disclosure: I'm a long-time PC user and have never owned a Mac... indeed until recently, I used to disparage them , but working in a UNIX environment + lots of online reading has made me see the light. All this to say that my questions come from a near total Mac newbie.

I'm a recent hire at a big university and have been given a very generous start-up package (translation: money isn't much of an issue, although I'd prefer spending $10K to $50K). Come ~ August or Sept, I'll need to buy a desktop and laptop plus perhaps (I'm less sure abt this one) some servers. A lot of my work involves running the R statistical program. To be productive, I need to run several scripts simultaneously - say 5 or 10. These scripts use a ton of CPU (like near 100%) and can run for hours if not days (or weeks!). I have considered buying some servers and installing UNIX on them, but then I had the thought that perhaps a single MacPro might be what I'm looking for.

Questions:
1) I've read several threads & links to online mags that are saying the 8-core is overkill, and that it doesn't improve performance. But is it the case that the biggest advantage of the 8-core processors is that you can run 8 different processes at full speed? I.e., could I be running 7 R-scripts and be doing normal computer activities (typing away in MS Word/surfing/etc.. ) on top of those with no noticeable slow-down?

2) Given my needs (a computer that could basically be used as if it were a server, such that it runs lots of different processes simultaneously), am I a poster-child for needing a Mac Pro, or is there something subtle (or not so) that I'm missing?

3) Would it be tough to call my MacPro with my laptop over the internet (when I'm working at home, at conferences, etc) so that I can control my computer from afar? I assume, given mac's unix core, this would be simple.

4) Finally, if anyone wanted to give me specs of their dream machine(s), I'd be all ears. I'm kind of thinking of a suped up Mac Pro (e.g., like 8 GB RAM, 750GB HD, 3Ghz), a 30" screen, and a smallish Mac Book to go along.

Thanks in advance!!!

 

[diehardmacfan]

you will have to instal mac osx server on it for monitoring.

 

[Lord Flashheart]

Yes osx server and it sounds like you need the octo. 8 gigs ram, get after market hd's.

 

[iSee]

One issue with the octo Mac Pro vs. say, two separate 3GHz quad machine, is the memory bandwidth. That is, all eight cores share the same bus to main memory. I don't really know how pronounced the impact on performance this would have though--I'm just speculating...

 

[NewbieNerd]

You definitely don't have to have OSX Server if you're comfortable with unix and sshing into your machine is enough. It is also easy enough to get the unix vncviewer (see darwinports and/or fink) or some other Mac-specific VNC client and VNC server (OSXvnc, for instance). Another alternative is the Apple Remote Desktop software, which you can find for cheap on eBay.

 

[trainguy77]

you don't have to have the server version of X to do what you want. Now the biggest question will be is if the programs you run require large amounts of memory bandwidth as well as CPU power as the memory bandwidth may be in short supply. I would personally go with a Mac pro thats decked out like you said. See how that goes and if its still a little sluggish when under heavy usage buy a cheap mini or imac for the day to day use and just have the mac pro cracking away, as the servers don't have the 8 cores. But I have a feeling that one mac pro should be all right. Its hard to say. Also for remote controlling the system this guide may get you somewhere http://guides.macrumors.com/Remotely_Controlling_another_Mac

 

[biggiemacman]

Don't buy a power mac. Bottleneck problems prevent their being worth it

Hi firstyearprof,

I'm also a statistician and my work recently purchased an 8-core powermac for me. I have been quite disappointed with its performance to date, relative to what I was expecting with 8 cores. Obviously, someone else had this problem too - this was recently posted on the R-Mac board:

I run R 2.4.1 on the 8-core Mac Pro. Tests using 2,4, and 8 threads
yielded somewhat disappointing results. The 4 thread process
is fastest. With 8 threads, all the cores max out at about 70% power,
and even then it is slower than the 4 thread process which maxes out the
4 threads at about 90-95%. This suggests the additional 4 cores on the
Mac Pro embarrassingly do not improve performance.

I'm guessing this has to do with the mac pro motherboard's
inability to keep all eight cores supplied with data from memory at an
adequate rate.

THUS - the new 8-core mac pros aren't what they're cracked up to be, at least not with what I can tell. Would love to be corrected on this... Take home = wait to buy an 8-core until mac has their head out of their butts and fixes the bottleneck.

 

[brooker]

Hi firstyearprof,

I'm also a statistician and my work recently purchased an 8-core powermac for me. I have been quite disappointed with its performance to date, relative to what I was expecting with 8 cores. Obviously, someone else had this problem too - this was recently posted on the R-Mac board:

I run R 2.4.1 on the 8-core Mac Pro. Tests using 2,4, and 8 threads
yielded somewhat disappointing results. The 4 thread process
is fastest. With 8 threads, all the cores max out at about 70% power,
and even then it is slower than the 4 thread process which maxes out the
4 threads at about 90-95%. This suggests the additional 4 cores on the
Mac Pro embarrassingly do not improve performance.

I'm guessing this has to do with the mac pro motherboard's
inability to keep all eight cores supplied with data from memory at an
adequate rate.

THUS - the new 8-core mac pros aren't what they're cracked up to be, at least not with what I can tell. Would love to be corrected on this... Take home = wait to buy an 8-core until mac has their head out of their butts and fixes the bottleneck.

Sorry to hear it hasn't been working out for you. I've been reading and thinking on these issues a lot lately.

The problem is not the memory bandwidth, but rather the swapping that happens when processes are moved between cores, but still need to access cache data on the die they left. The 2x2x2 config of the clovertowns exacerbates this problem.

There are two likely solutions that i have discovered:
1) Leopard: Every one hopes and expects that Leopard will have better thread scheduling and multi-core awareness. This should drastically improve performance.

2) In the mean time, it may be possible to run a virtual machine that is tied to some subset of your cores. So if your process runs well on 4 cores, keep it at that, and install a VMWare installation of Linux that gets access to the other 4 cores. Run a separate instance of your app within that virtual machine. Theoretically, this could keep processes on the same chips at least, and could therefore eliminate a lot of the cross-cache traffic that inhibits the usefulness of the full 8-core set up. You can get the VMWare beta by registering for free here: https://register.vmware.com/content/beta/fusion/registration.html


Hope that helps! I don't have an 8-core, so this is a bit of educated guess work on my part. If you get a chance to try it, please please let us know how it goes!

Thanks!

 

[Pressure]

Hi firstyearprof,

I'm also a statistician and my work recently purchased an 8-core powermac for me. I have been quite disappointed with its performance to date, relative to what I was expecting with 8 cores. Obviously, someone else had this problem too - this was recently posted on the R-Mac board:

I run R 2.4.1 on the 8-core Mac Pro. Tests using 2,4, and 8 threads
yielded somewhat disappointing results. The 4 thread process
is fastest. With 8 threads, all the cores max out at about 70% power,
and even then it is slower than the 4 thread process which maxes out the
4 threads at about 90-95%. This suggests the additional 4 cores on the
Mac Pro embarrassingly do not improve performance.

I'm guessing this has to do with the mac pro motherboard's
inability to keep all eight cores supplied with data from memory at an
adequate rate.

THUS - the new 8-core mac pros aren't what they're cracked up to be, at least not with what I can tell. Would love to be corrected on this... Take home = wait to buy an 8-core until mac has their head out of their butts and fixes the bottleneck.

Have you tried running with 5-, 6- or even 7-threads instead of just 8?

Note, I have no idea how that program works but remember that performance does not scale linear with the number of cores!

 

[observer]

Dream machine isn't just one machine

Look at MacResearch <http://www.macresearch.org/> for info and tools for XGrid. Statistics problems tend to be easy to run on grids, and if you could get access to a lab full of iMacs, you'd have a supercomputer available for free. Add to that a big iMac on your desk for writing, and a 4-core Mac Pro with 8 GB and some biggish disks for the occasional problem needing huge files. And a MacBook for travel.

The combination of several separate machines is dramatically more powerful than one monster, unless you've got one problem that needs the monster to run at all.

XGrid is valuable for managing sequences of tasks on a single dual-processor machine, too.

Peter

 

[trainguy77]

THUS - the new 8-core mac pros aren't what they're cracked up to be, at least not with what I can tell. Would love to be corrected on this... Take home = wait to buy an 8-core until mac has their head out of their butts and fixes the bottleneck.

This is correct however this one you can't blame on apple.....phone up intel get on there case. Dell systems have the same problem.

 

[johnee]

I don't know the intel bus subsystem, but it sounds like it's severely constrained. I would go with the grid suggestion.

 

[dogbait]

Intel are integrating the memory controller into their CPUs in 2008 much like AMD did a few years ago. It should solve this problem if that's any consolation. However if you want something here and now the only single system with eight cores and enough memory bandwidth to feed them all would be an AMD quad processor box. Not OSX friendly unfortunately and very expensive, since AMD have no quad core CPUs yet. However, in the next six months AMD are coming out with quad core processors which should spank Intel handily when comparing heavily multithreaded apps with more than 4 threads.

I am no AMD fan boy, I assure you. But it is 'horses for courses' at the end of the day, and unfortunately, despite the fact that the Xeon is a faster processor than AMD's Opteron, it has a narrower memory bus. The difference in memory bandwidth between Intel and AMD platforms is about 1:2.
http://www.techreport.com/reviews/2006q4/xeon-vs-opteron/index.x?pg=5

 

[gnasher729]

I don't know the intel bus subsystem, but it sounds like it's severely constrained. I would go with the grid suggestion.

I'd check the price for two 2.66 GHz quad core MacPros and for half a dozen MacMinis. (Mac Minis wouldn't be recommended in an environment where things tend to walk away on their own; too easy to pick one up when nobody's watching)

 

[2pac]

your suggestions are priceless. Its only his way to choose.

 

[biggiemacman]

Why the 8-core is so SLOW...

It is my understanding that there are two problems with the 8-core that make it slower than it should be for multi-threading:
1) the bus bottleneck
2) the Tiger OS doesn't know how to allocate multiple processes over 8 cores.

I've heard that of these two, the last is the biggest problem now, and that this may get corrected for Leopard. That gives me hope - if my 8-core starts running better after Leopard, then I only have to wait till Oct to get the machine I thought I was getting... Any thoughts???

 

[crazzyeddie]

Look at MacResearch <http://www.macresearch.org/> for info and tools for XGrid. Statistics problems tend to be easy to run on grids, and if you could get access to a lab full of iMacs, you'd have a supercomputer available for free. Add to that a big iMac on your desk for writing, and a 4-core Mac Pro with 8 GB and some biggish disks for the occasional problem needing huge files. And a MacBook for travel.

The combination of several separate machines is dramatically more powerful than one monster, unless you've got one problem that needs the monster to run at all.

XGrid is valuable for managing sequences of tasks on a single dual-processor machine, too.

Peter

This does sound like a viable option. Given that you can get the iMac 17" for a mere $1099 (or maybe even less for large EDU purchases) you could have alot of power and a lab for your students. Each iMac would have a dual 2.0ghz processor and 1GB of RAM... more than enough for use in a powerful XGrid cluster.

Add to that a Quad core 2.66 or 3.0 Mac Pro and Macbook (Pro) for yourself and it would be wonderful. You could then get Apple's Remote Desktop (10 client for $149 or unlimited clients for $299) and you could manage the entire lab, including software updates and GUI or terminal access, from anywhere in the world.

You might even be able to get additional funding from the university for this and create an even larger lab (now or down the road!).

EDIT: I saw someone above mention Mac Minis as well. Those would be a good choice if all you wanted the machines for was number-crunching, but if you wanted students to use these machines at all you would need to add a monitor. Just for comparison, a Dual Core 1.66ghz Mac mini with 512MB of RAM is $579 ($647 with 1GB of RAM), so you could get almost 2 of them for the price of an iMac. However I still think the iMacs are a better choice... more usability, more power and longer life due to a better GPU, etc...

 

[firstyearprof]

thanks!

hi everyone,

Thanks for all the replies. I've learned a good deal. It sounds like I might be better off buying a laptop now, and waiting until Leopard arrives to see how it deals with the 8-cores. If I need desktops before then, I might get more bang for my buck by using clusters of smaller computers, which are more efficient at handling their CPUs, than buying one do-it-all 8-core.

I must admit that I find it a little strange that apple would have introduced the 8-core before the OS it runs on was able to take advantage of it ... After using windows machines for so long and just recently joining the Apple bandwagon, I guess I had kind of gotten swept up in apple-mania, and thought they could do no wrong.

Once again, thanks for all the advice...

 

[observer]

It's not fair to say that the OS doesn't handle 8 cores -- it's more that it doesn't handle them efficiently, once things get past a certain point. The issue is that each core has its own cache, which it uses very efficiently, and if the task given to each core fits in cache then everything gets done very fast. For some benchmarks, the 8-core machine is almost twice as fast as the 4-core. However, when there are more than 8 tasks, or the tasks require swapping out from cache, the OS may move threads from one core to another, and may do it badly -- moving across from one of the two chips to the other. On some benchmarks, the 8-core is no faster than the 4-core, even though all 8 cores are chugging away.

It's likely that Leopard will address this issue to some extent, but it's not as if it's clear what the solution should be. Using the multiple cores in these machines as a shared-memory parallel computer requires a shift in thinking in both application and OS.

XGrid is a way to do very simpleminded parallel computing on a roomful of machines, like a lab. If the lab is already there, it's a great tool. But I don't think that implies that a stack of MacMinis is better than an 8-core MacPro of equal cost.

Actually, what I'd like is for you to spend your money on a variety of machines, including an 8-core Pro and a stack of minis, and then figure out how to do statistics on them in the fastest, cheapest, bestest way possible. And then I can spend less of my money.

Peter