Based on the info you have posted, this is a LuxRays bug. The referenced file is one of their own internal source files. I am the author of Fractal Architect for Mac and iOS. I am not having any issues with my own app. In fact, it looks like Apple has fixed issues I reported back in Catalina. I have had an OpenCL app on MacOS since 2009. And yes OpenCL has been broken 5 years ago when El Capitan was released, but since then it has been robust for single GPU renders. OpenCL has been problematic for multiple GPU rendering, whereas Metal works properly. I have not yet retested the multiple GPU kernel scheduling bug in Big Sur.

device const sphericalparams * params [[buffer(2)]] --- Metal ... xyout[index].x = params->x + params->scale * x; xy_out[index].y = params->y + params->scale * y; vs float scale, float x0, float y0 --- OpenCL xyout[i].even = x0 + scale * x; xyout[i].odd = y0 + scale * y; The compiler code optimizer most likely likes the OpenCL approach. The params -> indirection may be costly.

Essentially this is the same as setting up a new Mac. You will need to import the certs that you had imported. I use git from the command line to download my apps' source onto the new Mac. The certs are needed so you install your app on a iOS device. For Mac apps, the certs let you upload your app to the app store. Notarized apps need certs too.

Xcode 12 takes 28 GB installed + a place to hold the compressed app image of about 14Gb, that is 42 Gb. The compressed image can be deleted AFTER the install completes. The error message is legitimate.

Xcode 12 is BIG. Its possible your hard drive is almost full, so the OS has to compress your SWAP space, which really slows things down. So check your disk free space. 500 GB SSDs are not that big.