Why is there such high variation on the render rates of the same scene from one render attempt to the next?

[Deleted member 1121028]

Honestly, I don't think you understand what fault I'm describing. :-/

I don't think you understand how it works.
That being said, it's not really important, I (sincerely) wish you the best for you project o/

 

[K.T.L.]

Daz has many faults, but not the one OP describe (or maybe he just broke a major flaw in the monte carlo method, who knows?).

It certainly does. Happens on my system as well and searches have shown that it's a very common IRay issue. It doesn't release VRAM after completing a render, even if all the render windows are closed. If your GPU is a little tight for spare memory, it can tilt subsequent renders into CPU processing. I have to shut Daz down between renders to get around this annoying issue. That makes batch rendering almost pointless.

 

[Deleted member 167032]

You could try Man Friday's batch render facility. It closes DAZ completely i believe adn then strart it up with next scene to render. This may break the memory cache that DAZ seems to hold onto like Lord of the rings's ring

It certainly does. Happens on my system as well and searches have shown that it's a very common IRay issue. It doesn't release VRAM after completing a render, even if all the render windows are closed. If your GPU is a little tight for spare memory, it can tilt subsequent renders into CPU processing. I have to shut Daz down between renders to get around this annoying issue. That makes batch rendering almost pointless.

 

[K.T.L.]

You could try Man Friday's batch render facility. It closes DAZ completely i believe adn then strart it up with next scene to render. This may break the memory cache that DAZ seems to hold onto like Lord of the rings's ring

I'll look into that. Thanks

 

[Deleted member 1121028]

It doesn't release VRAM after completing a render, even if all the render windows are closed.

With all due respect, it doesn't matter, even an 'unpurged' scene fits VRAM or does not (and fallback to cpu). Variance in iterations/sec (without cpu fallback) for a same scene is a way more concerning problem (as OP describe).