Does more RAM make simulations bake faster?

Blender's renderer and external renderer export

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Deaxman123
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Does more RAM make simulations bake faster?

Post by Deaxman123 » Wed Jul 24, 2013 2:53 pm

I just bought a new computer with 16 GB RAM and a GTX 680 Graphics Card. I used to have a weak computer with 4 GB RAM and a ATI Radeon HD 4650 Graphics Card. With the new computer cycles is working great and much faster :)

But when i bake a fluid simulation it takes the same time as before :(

I would think that RAM makes baking faster but does it?

And if yes why isn't it working.

Thank you very much :)

sendodo123
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Post by sendodo123 » Mon Jul 29, 2013 3:54 am

I think ram doesn't increase the speed very much. But the main point of increasing ram is to prevent it doesn't have enough ram and stops while baking

Deaxman123
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Post by Deaxman123 » Mon Jul 29, 2013 10:27 am

Ok thanks but I think it's baking too slow can I speed it up somehow. I can't believe that it should take so long to bake a fluid simulation.

stiv
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Post by stiv » Mon Jul 29, 2013 6:09 pm

As long as you have enough RAM to keep from swapping (which is horribly slow) or running out, you should be good.

Fluid sims are computationally expensive. The more CPU you can bring to bear, the better. Computational Fluid Dynamics is one of the reasons people build super computers.

I don't know if the fluid sim stuff is multi-threaded. I suspect not.

zeitrafa
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Faster Baking

Post by zeitrafa » Tue Jul 30, 2013 3:39 pm

I know Bakingdata for Simulation is written to hdd, for caching reasons. Thats the reason why its good to save the file before baking.
I thing a ssd or a fast hd or defragmenting your 80 of 100gb free hd could be useful, because blender writes and reads this data from hdd.

look here :
http://www.blender.org/development/rele ... nd-baking/

Caching

As animation is played, each physics system writes each frame to disk, between the simulation start and end frames. These files are stored in folders with prefix blendcache, next to the .blend file. The cache is cleared automatically on changes. Note that for the cache to fill up, one has to start playback before or on the frame that the simulation starts. The cache can be freed per physics system with a button in the panels, or with the Ctrl+B shortcut key to free it for all selected objects.

arittner
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Post by arittner » Mon Aug 12, 2013 1:29 pm

stiv wrote:As long as you have enough RAM to keep from swapping (which is horribly slow) or running out, you should be good.

Fluid sims are computationally expensive. The more CPU you can bring to bear, the better. Computational Fluid Dynamics is one of the reasons people build super computers.

I don't know if the fluid sim stuff is multi-threaded. I suspect not.
You can chosse the threads near under the baking button of the domain object.

br, josh

Deaxman123
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Multiple Threads???

Post by Deaxman123 » Mon Aug 12, 2013 1:38 pm

Thanks a lot :)

But what does multi-threading do?
And what would the best number of threads be?

WilkyBoy
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Post by WilkyBoy » Mon Sep 30, 2013 6:55 pm

I ran a water simulation with 32 simulation threads, however, during the simulation, blender was running 47 threads and afterwards it was running 46.

Does anyone know what that option does?
//Benjamin
\\I play games. too many games.

WilkyBoy
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Post by WilkyBoy » Mon Sep 30, 2013 11:12 pm

UPDATE: Selecting simulation threads does multi thread the simulation process,
however whether it makes it faster or not I don't know.

One thing to bear in mind, when you finish the simulation (or in my case cancel it) it only appears to drop one thread, but keeps the others running

Blender crashed before my bake, so it was a good chance to look at thread numbers:

Before start of bake = 15 threads
bake = 32 threads (47 threads)
end of bake = (4 threads dropped)
bake = 32 threads (79 threads)

or 15 + 32 - 4 + 32 = 79

This may be cause for concern as too many threads can crash your computer
100s of threads per application is a cause for concern and 1000s will almos certainly kill it.

As for speed, I'll do some time tests tomorrow and let you know.

All the best,
//Benjamin
\\I play games. too many games.

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