64-bit sieving

[paleseptember]

Sorry, me again.

Is there a significant speed improvement running the 64-bit version of the sieve compared to the 32-bit version?

If so, is there a way to run the 64-bit version on Windoze xp pro (32-bit version)? Sorry if that's a daft question!

To the knowledgeable people who reply, thanks in advance!

[mdettweiler]

Originally Posted by paleseptember

Sorry, me again.

Is there a significant speed improvement running the 64-bit version of the sieve compared to the 32-bit version?

If so, is there a way to run the 64-bit version on Windoze xp pro (32-bit version)? Sorry if that's a daft question!

To the knowledgeable people who reply, thanks in advance!

First of all, yes, you do get about double the speed from running a 64-bit sieve program versus a 32-bit one. (This is in contrast to LLR, PRP, and other similar work, for which there is not much of any difference between 32-bit and 64-bit.)

As for running a 64-bit program on 32-bit Windows: nope, sorry, that won't work. You have to have a 64-bit operating system to run 64-bit programs. (Not a daft question, though; it is a common point of confusion, especially since most modern processors are 64-bit compatible even though people usually run 32-bit operating systems on them. )

[paleseptember]

Originally Posted by mdettweiler

First of all, yes, you do get about double the speed from running a 64-bit sieve program versus a 32-bit one. (This is in contrast to LLR, PRP, and other similar work, for which there is not much of any difference between 32-bit and 64-bit.)

Looks like my efforts would be better suited to PRPing then :) Let those with shiny linux systems run the sieving! (Or vista, I suppose )

[mdettweiler]

Originally Posted by paleseptember

Looks like my efforts would be better suited to PRPing then :) Let those with shiny linux systems run the sieving!

Well, don't get me wrong, 32-bit systems still do fine at sieving, too--in fact, they usually don't become inefficient until the sieving progresses to a relatively high level (or if there are plenty of 64-bit machines to handle the sieving easily by themselves, as doesn't seem to be the case here). So, you'd probably be fine with either sieving or PRP'ing for this project.

Phil, would you recommend that the project as a whole focus its efforts on sieving at the moment, or are sieving and PRP both at roughly the same priority level given the current sieve depths and whatnot?

[philmoore]

Originally Posted by mdettweiler

Well, don't get me wrong, 32-bit systems still do fine at sieving, too--in fact, they usually don't become inefficient until the sieving progresses to a relatively high level (or if there are plenty of 64-bit machines to handle the sieving easily by themselves, as doesn't seem to be the case here). So, you'd probably be fine with either sieving or PRP'ing for this project.

Phil, would you recommend that the project as a whole focus its efforts on sieving at the moment, or are sieving and PRP both at roughly the same priority level given the current sieve depths and whatnot?

Maybe Geoff could clear this up for us. I am assuming that the 64-bit version of sr2sieve uses the 64-bit instructions through optimized assembly code. If so, why can't it be run even in a 32-bit operating system? It certainly seems it would be a strong advantage to run it on a 64-bit processor.

I estimate that PRP-ing to 2.1 million would take about the same amount of time as sieving to 100 trillion on a 32-bit machine. That would be a good sieve depth at that level, so I would rate the priorities as roughly equal for now.

[geoff]

Originally Posted by philmoore

Maybe Geoff could clear this up for us. I am assuming that the 64-bit version of sr2sieve uses the 64-bit instructions through optimized assembly code. If so, why can't it be run even in a 32-bit operating system? It certainly seems it would be a strong advantage to run it on a 64-bit processor.

It can't be done (At least not in Windows or Linux). The 64-bit instructions are not simply additions to the 32-bit instruction set, they use incompatible opcodes. The same binary opcodes are interpreted as different instructions depending on whether the process is running in 64-bit mode or 32-bit (compatibility) mode. Windows and Linux 32-bit kernels are not able to start 64-bit processes because they themselves run in 32-bit mode. But Windows and Linux 64-bit kernels can start processes in either mode.

I think the main reason sr2sieve is faster in 64-bit mode is that it uses a method of modular arithmetic that does both floating point and integer multiplication. While the floating point multiplication is about the same speed in 32-bit and 64-bit modes, the integer multiplication is 3-4 times faster in 64-bit mode.

[Kevin]

If your processor supports it (ie, is VT enabled), there's a way to run a 64 bit OS on a virtual machine within a 32 bit OS. You get the benefits of 64 bit computing without having to change your existing OS.

[henryzz]

Originally Posted by Kevin

If your processor supports it (ie, is VT enabled), there's a way to run a 64 bit OS on a virtual machine within a 32 bit OS. You get the benefits of 64 bit computing without having to change your existing OS.

oh i didnt know that
will virtualbox do it

[mdettweiler]

Originally Posted by henryzz

oh i didnt know that
will virtualbox do it

VirtualBox is supposed to support various hardware virtualization stuff, so yes, I would imagine it would work fine. (Hey, I need to try that myself, since I already use VirtualBox frequently for 32-bit virtual machines! )

[Kevin]

All the information I know about this subject is coming from the thread for Ars Technica's ABC@home team (http://episteme.arstechnica.com/eve/...007328831/p/10), since that project has the same benefit of a 64-bit OS. Pretty much everything I'm saying on this subject is coming directly from there.

Apparently virtual box doesn't let you run a virtual 64 bit os from inside a 32 bit one, but vmware does. All of the quad cores and E6xxx/E8xxx are VT enabled, but you might have to enable some setting in the BIOS.

[henryzz]

sorry to bring up an old subject but there is a new version of virtualbox that claims to run a 64-bit operations system in a 32-bit host