X4 Ray Tracing - Optimal CPU

[Ian Pellant]

Thanks James,

Yes, I ran X4 with 4 copies of the test plan and it queued them up and ran sequentially. All times were the same as the single test run.

The pain is tuning the settings for the ray tracer to get desired image quality. Times go up exponentially and hours or days can elapse before the balance is found. It used to be weeks.

Found a few reviews of the FX8150 that compared it with the i7 2600. Many of the tests indicated that the AMD was significantly slower than the Intel... until the AMD was overclocked to about 4.5GHz (without OC it bumps up to around 4.2GHz). Add water cooling and it will OC to 5GHz or more. 4.5GHz is okay on air cooling.

The CPU pricing is Aus $292 for the FX8150 and $334 for the i7 2600; but the AMD can use more expensive / faster DIMM so the total costs come out about the same.

From the web reviews it seems that most application code (compiled on Visual Studio) will not be optimal for high core count processors. Win 7 doesn't spread loads across cores. That is expected to be improved in Win 8. AMD have 2 cores per module - 8 cores / 4 modules. Intel have 4 cores with hyperthreading to virtualise cores.... at present, Win 7 and most code compilers favor the Intel model.

Single thread code seems to run 50% slower on the AMD compared to the Intel. With Overclocking the AMD comes closer.

In the longer view, AMD may be on the right track.... but Intel seem to have the speed edge today.

Cheers.

[Ian Pellant]

James,

Post script:

Have you tried running several intances of Chief at the same time and seeing if that loads up the cores more effectively?

It's am old Chief trick:
After starting Chief Architect once, start another session while holding down the <Ctrl> key. Then with 2 instances of Chief open, run the ray tracer in each.... halves the overall time?

Hypothesis:
With 8 cores, run 4 sessions of Chief and ray trace 4 plans at the same time.

Cheers.

[marty]

Ian you havent mentioned overclocking on the i7 2600k. I have mine clocked to 3.7 but reviews suggest it will go over 4.5 with suitable cooling.

[Ian Pellant]

Hi Marty,

Darn it.... oc the i7...

I'm using TechBuy (www.techbuy.com.au) as my supplier... they added some new i7 processors yesterday. But they all need really fast RAM to get the most out of them. RAM over 1600 is uncommon and expensive, in Aus. The new Intels seem to be asking for 2100 or even 2400 RAM.... If the i7 needs fast RAM to overclock then it really could be pricey... I dunno.

Web reviews indicated that the AMD with memory faster than 1600 will overclock fine (spent a lot of time parsing the motherboard, memory web sites for the best choices, then trying to find them on TechBuy was tedious).

I just did a 2 session Chief test, running the test plan ray trace simultaneously. Ran fine... but each ray trace took exactly twice as long as running a single session. In other words - no time improvement over running a single session queueing the ray traces conseqeutively.

I expected that since it ran on an old Intel single core, which hyperthreads to pretend it is 2 cores. (Intel: the core count pretender?)

So: now the big question is whether the AMD FX can run multiple sessions of Chief and the ray tracers simultaneously, at no speed loss in each session.... or can Intel do it better?

From what I read on the web reviews, they didn't load up 4 copies of an application and run those simultaneously. Possibly the AMD FX will run applications in its' modules (4 modules, 2 physical cores per module... thread sharing between those 2 cores... 4 virtual computers at the same time?).

If Chief has not been compiled to support multiple instances so each can run in a separate core... Doug: why not?

Cheers.

[marty]

I had a look on line and it seems 4.5Ghz to 5Ghz is easily achievable with the i7 2600k
http://benchmarkreviews.com/index.ph...&limitstart=14

[Ian Pellant]

Marty,

Dare I ask you to run the test plan ray trace on your computer; then overclock it and see what the difference is?

Thanks.

[jpremodeler]

Marty,

Dare I ask you to run the test plan ray trace on your computer; then overclock it and see what the difference is?

Thanks.

I had a tough time at 5.0 keeping stable. I am air cooled, and my ram config only let me use 1 fan on my heat sink. If you can keep the 2600k stable at 5.0 with air, hat's off.

I did not benchmark my pre/post overclock, but it was a decent bump in speed. If I burn the cpu in a year, the time saved is worth it.

[Allen Brown]

James,

Post script:

Have you tried running several intances of Chief at the same time and seeing if that loads up the cores more effectively?

It's am old Chief trick:
After starting Chief Architect once, start another session while holding down the <Ctrl> key. Then with 2 instances of Chief open, run the ray tracer in each.... halves the overall time?

Hypothesis:
With 8 cores, run 4 sessions of Chief and ray trace 4 plans at the same time.

Cheers.

Ian, you sure about that? You cannot open the same plan in two sessions of Chief, unless you do a "file>save-as" and change the name.

[Ian Pellant]

File locking will prevent a plan being opened by another session of Chief....

I need to ray trace many plans. Not many views of a single plan. (Brochures only need one view per house plan).

So what I tested was opening 2 copies of the test plan and ray tracing them simultaneously. I did not open the same plan file twice. In practice, they will be plans of different houses.

On my old P4 the cumulative processing time for two simultaneous sessions was the same as running from a single session of Chief and batch queing two ray traces. No time gain.

Overclocking has shown promise. The over clock ratio gives a very linear improvement in the ray tracer - probably due to it being almost completely CPU bound. Turning on overclocking with a software tool once Chief is loaded seems the best way to overclock - it allows overclocking to be turned off for "normal" use after ray tracing, which reduces power consumption, heat, system stress, etc.

Cheers.

[lbuttery]

Allen:

turn off "file locking" in preferences

it is highly recommended to not make edits to both plans while they are open this way - could lead to file corruption

probably best to clone the plan before doing this - for safety

I have used this method for doing presentations

instance A shows one view or set of views

instance B is then used to move around the plan to show other view(s)
while being able to hop back to instance A view(s) and not lose postion in either

this can also be done while comparing Chief X3 versus chief X4 for example

Lew