iray render doesn't progress

Passero

I sometimes have a render where the progress is stuck but the rendering continues and I see new iterations only the % doesn't advance. 

For example the scene I am currently rendering is stuck at 10.53% since +/- iteration 100. I am currently at itteration 460 and it is still 10.53%. 
I also don't see the image change that much. There is still quite a bit of noise in the render so I am wondering what could be the reason for this? 

I believe I have lit the scene properly. It's an inside scene where I use a dome for the exterior with HDR image and the windows all have the iray glass shader. 
I also added some lights inside to properly light the subject but even my subject has a fair bit of noise. 

I am using the default rendering setting but only increased the max time from 7200 seconds to 72000 seconds. 

BeeMKay

You could set the noise filter to "on" to improve the quality (but that will render even longer).

Also, in tonemapping, try setting the shutter speed to 100, and f/stop value to around 5.6, or even lower to 2.8. That should give more light to your scene (also, you don't have to stop your render for this. At the left hand of the render screen, you can open several render settings, which can be manipulated during the render). See if this speeds up the render time.

Testing6790

It'll progress. I don't know why it does this, but the rendering isn't linear from my experience. In my current scene I get less than 1% convergance for the first ~10 min / 500 iterations and then it starts cruising. I normally stop at 10% convergance just because I'm impatient.

I've read that a good trick with physically based renders to improve quality is to render it at twice the size you want and then rescale it down after. Apparently the 2x smaller at 50% convergance is "cleaner" than the 1x at 100%, from what I've read. I still need to try it.