Insane memory footprint difference between progressive and bucket sampler?

[Art48]

I notied that scenes tend to use more RAM with the progressive sampler. But I got a beast here which is a really simple scene. 1 plane and a couple hundred instances of an 8-sided cylinder. Rendering at 30k the bucket sampler uses close to 20GB of the 64GB of available RAM which is totally reasonable regarding having 3 render elements on top. When I switch to progressive sampler, the RAM completely blows up and max crashes. Is this expected behaviour? What could be the issue? This is not a high priority problem for us at all, we render mostly using the bucket sampler and the rendering is already finished and delivered, I just found it really curious.

Max 2016 and VRay 3.60.03

I may be able to provide a scene if neccassary.

[yavor.rubenov]

Hello,

This is expected - one of the main differences between the bucket and the progressive sampler is that the progressive one needs to allocate buffers for the whole image output and for each render element at the start of the render. It also has to allocate additional memory for the image AA filtering buffers which in the progressive case have to be proportional to the output image size.
The bucket sampler on the other hand needs much fewer buffers - only for the currently rendering buckets.
So if you render such big resolutions (30k) - it's better to use the bucket sampler.

Best regards,
Yavor

[Art48]

I see, thank you for the clarification.