332.2M - 333.9M (aka 100M digit range)

[VBCurtis]

I didn't ask what method you used to determine 400M; I asked how long P95 takes to do that stage 2, instead of GMP-ECM.

The fact you found GMP-ECM most efficient at 1/10th of its default B2, where I usually find GMP-ECM most efficient at default to 2x default B2, suggests to me that GMP-ECM is not a great choice for the numbers you're working on. That's why I asked how P95 does instead of GMP.

[VBCurtis]

Originally Posted by chalsall

Sigh... Why do we not understand how hyperthreads work (repeatedly)?

It's a bit like being asked to teach a graduate course, but then have to entertain kindergarten children....

Chris-
Can you explain what you mean by this? If I understand your implication, it may be you who needs to freshen your understanding of HT, specifically that different programs respond quite differently to using HT "cores".

[Uncwilly]

Can a mod please move all of the off topic replies from 581 forward to a new thread please?

[Gordon]

Originally Posted by VBCurtis

I didn't ask what method you used to determine 400M; I asked how long P95 takes to do that stage 2, instead of GMP-ECM.

The fact you found GMP-ECM most efficient at 1/10th of its default B2, where I usually find GMP-ECM most efficient at default to 2x default B2, suggests to me that GMP-ECM is not a great choice for the numbers you're working on. That's why I asked how P95 does instead of GMP.

Thought I had answered it, sorry.

P95 - 117 secs

GMP - 89 secs

[LaurV]

Originally Posted by Gordon

Task manager shows 8 threads, all at about 50% or so

Oh boy...

Edit: agree with Uncwilly that a mod should move out or delete the futile posts, and agree with RDS that some of us are worthless..

[chalsall]

Originally Posted by VBCurtis

Can you explain what you mean by this? If I understand your implication, it may be you who needs to freshen your understanding of HT, specifically that different programs respond quite differently to using HT "cores".

Sure...

Those who are serious about their code (like George) work so close "to the metal" that getting 50% CPU utilization (with hyperthreading enabled) is exactly what we want.

I would argue that sub-optimal code (which does anything useful) will almost never get to 100% CPU utilization, even with hyperthreading enabled, because of memory bandwidth issues and lack of explicit affinity.

Happy to be counter argued....

[Prime95]

Originally Posted by chalsall

Those who are serious about their code (like George) work so close "to the metal" that getting 50% CPU utilization (with hyperthreading enabled) is exactly what we want.

Happy to be counter argued....

Code efficiency has nothing to do with Task Manager's CPU utilization number.

Task Manager simply measures the percentage of time the OS had a process available to assign to the logical CPU.

The most common source of confusion is that prime95 defaults to 4 workers on a hyperthreaded quad core. With only 4 active threads and 8 logical processors you get a 50% CPU utililization. We must then explain to newbies that since prime95 is super-efficient, the 4 physical CPUs are actually getting used to their maximum.

Gordon's original post of "Task manager shows 8 threads, all at about 50% or so" is a different case entirely. The way I read that statement, we have 8 workers and 8 logical cores and we should be seeing 100% logical CPU utilization. He must have some kind of problem with affinity settings that is preventing the OS from letting the workers occupy all 8 logical CPUs.

[Gordon]

Originally Posted by Prime95

Code efficiency has nothing to do with Task Manager's CPU utilization number.

Task Manager simply measures the percentage of time the OS had a process available to assign to the logical CPU.

The most common source of confusion is that prime95 defaults to 4 workers on a hyperthreaded quad core. With only 4 active threads and 8 logical processors you get a 50% CPU utililization. We must then explain to newbies that since prime95 is super-efficient, the 4 physical CPUs are actually getting used to their maximum.

Gordon's original post of "Task manager shows 8 threads, all at about 50% or so" is a different case entirely. The way I read that statement, we have 8 workers and 8 logical cores and we should be seeing 100% logical CPU utilization. He must have some kind of problem with affinity settings that is preventing the OS from letting the workers occupy all 8 logical CPUs.

I was reporting what I saw when running 4 instances of gmp-ecm. Is that the os doing the threading or is gmp-ecm multi-processor aware?

[chalsall]

Originally Posted by Gordon

I was reporting what I saw when running 4 instances of gmp-ecm. Is that the os doing the threading or is gmp-ecm multi-processor aware?

We don't yet know exactly what is happening.

Further empirical testing would be useful.

[VBCurtis]

GMP-ECM is not thread-aware. 4 GMP processes on 8 logical cores should read 50% across all 8 logical cores, as windows will bounce a process from core to core to try to "use" all available cores (I think). If some affinity mask is set, you might get 4 at 100% instead.

I believe GMP-ECM runs better with more processes than physical cores; on an old i7 laptop, 8 processes ran about 20% more curves per day than 4 processes. I never ran stage 1 and stage 2 separately, and I haven't found P95-ECM (using FFT's) to have a similar speedup; but you might still benefit from 4x P95 and 2x GMP stage 2 at the same time.

Chris- I definitely misunderstood your posting about HT, sorry.

[chalsall]

Originally Posted by VBCurtis

Chris- I definitely misunderstood your posting about HT, sorry.

Absolutely no problem. I often make mistakes, and want to be corrected.

Peace, brother!