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.

[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

[Doug Park]

There is no advantage to running multiple ray traces simultaneously in X4. Ray tracing is a highly parallel task that takes advantage of all the cores most of the time.

Any advantage that you might have during the few times that the ray tracer is not taking full advantage of all the cores would probably be lost in task switching overhead.

[Ian Pellant]

Thanks Doug,

I suspected that may be the case.

Indications are that the AMD FX18150 would require overclocking to match or exceed the Intel 17 2600.

Cheers.

[marty]

Ian I am not a tech type user. I had my PC overclocked when I bought it and thought it was beyond the average user to make changes.

Is there a program which can do it?

[marty]

Ian I did a bit of looking and have cranked my PC up to 4.2Ghz. I ran the windows experience index and the processor rating increased from 7.5 to 7.7 (7.9 is the highest ranking) The SSD rates at 7.8

I downloaded your sample but there are no trees. Did you export the plan before zipping?

[Ian Pellant]

marty,

It depends on the processor and the motherboard vendor.

My old box is a "Shuttle" - over the years I've built 3 others based on AMD... mine is an Intel P4 660 3.6GHz. Shuttle provide what they call "XPC Tools" - a software utility for monitoring the system (temperatures, fan speed, etc) and overclocking. It makes it easy to experiment with overclcoking. If the system locks, a reboot will clear the settings. Quit XPC Tools and the system is back to normal. My old box overclocks to just under 4GHz by bumping the FSB from 200 up to 220. Ray tracing improvement seems in a linear relationship with the system speed.

Intel tend to discourage overclocking for a few commercial reasons as well as technical. It was fuin to run the Intel Processor ID utility (can find it on the Intel web site) and see the big red warning that the system was overclocked.

The AMD FX-8nnn series processors black edition are "unlocked" to almost encourage overclocking. The Asrock motherboards come with Turbo Boost utilities to allow overclocking. The nominal bump top speed of the FX-8150 is 4.2 GHz. It can easily be boosted to 5GHz on air cooling; perhaps more. WIth liquid cooling, it should be able to run happily at 5.5GHz.

If your motherboard manufacturer did not provide software tools for overclocking, then it can be done manually by entering the BIOS at boot time and setting the core cpu speed or voltage, the FSB (Front Side Bus) speed and the memory speed or voltage. If you get it wrong the system won't boot.... that is why systems intended for enthusiasts will have "system reset" button somewhere in a recessed hole on the back of the computer... without that, using the BIOS clear jumper on the motherboard to clear the settings (or remove the 2032 battery for a few minutes).

If you web search you may find an article specific to your CPU and motherboard.

If you have a run of the mill, brand name system, then the manufacturer has probably tried to discourage overclocking... it will "void the warranty".

I like Shuttles because they are compact and very cost effective. Also means the case, motherboard and power supply are all warranteed by the same company and they do proide overclock tools. (see www.shuttle.com). Shuttle will cost about Aus $1400 for an i7 2600 with CPU, memory, hard drive, optical drive, Win 7 Pro. They do not have a box for the AMD FX-8150... which is a big hint that they are not favouring AMD this year. It will be my i7 choice.

Cheers.

[Ian Pellant]

marty (Gordon)

The trees are images from the CA X4 Core Plant libraries. If you have all the core libraries installed, they should be there. Chief should have flagged warnings ig it couldn't find them.

Cheers

[marty]

OK I played around a little more.
I reset the processor to 3.4Ghz and got a time of 1:27min
Went back and changed it again this time to 4.5Ghz and got a time of 55 secs which was slower than the 47 sec result at 4.2Ghz.????
Re did the ray trace and got 55 again.

I am not sure what is happening but regardless the improvement is at least 30% which is quite significant

[marty]

Last time - I am now going to do some work!!

Re set to 4.2Ghz and got 57, 55, 58 seconds so the 47 seconds first time up was a one off? Is it the clock thats a problem?

I think I will leave it at 4.2 as the small improvement going to 4.5 doesnt seem worth the potential problems that could come with pushing the system. I have an extra big fan but no other special cooling features.