No generation with VULKAN backend for some parameters

[olivbrau]

Hi,
I've tried the VULKAN backend and encountered strange results.
(I used model 2.1, but the issues arise also with other models)

1) no image if no --vae-on-cpu parameter
sd -m .\v2-1_768-nonema-pruned.safetensors --sampling-method euler --steps 20 -H 512 -W 512--type q8_0 -p "a cute birman cat"
--> the generation phase is realised, and then during the phase where the logs says "decoding latents", suddenly the simulation ends suddenly and no image is written
--> if I add --vae-on-cpu, it works

2) black image for some image size
sd -m .\v2-1_768-nonema-pruned.safetensors --sampling-method euler --steps 20 -H 512 -W 512 --type q8_0 -p "a cute birman cat" --vae-on-cpu -->OK
sd -m .\v2-1_768-nonema-pruned.safetensors --sampling-method euler --steps 20 -H 768 -W 768 --type q8_0 -p "a cute birman cat" --vae-on-cpu -->KO the phase "generating image"hangs and the script ends suddenly
sd -m .\v2-1_768-nonema-pruned.safetensors --sampling-method euler --steps 20 -H 512 -W 832 --type q8_0 -p "a cute birman cat" --vae-on-cpu --> KO the process goes until the end, but the image is totally black
For the 2 last examples, the same command with CPU backend works fine

[stduhpf]

• Does it work if you use --vae-tilinginstead of --vae-on-cpu?
• Can you try sync: update ggml #509 to see if it fixes anything?

[olivbrau]

With --vae-tiling instead of --vae-on-cpu, it worked

For the ggml update, I don't know how to try, I've not yet implemented a build environnement for this stable-diffusion.cpp project

[stduhpf]

The ggml update might fix the black image. Not sure about what's causing the crash when generating at 768x768, maybe you're just running out of memory?

[olivbrau]

So I'm waiting for the next release ! :-)

For the crash, I think you're right : with 512x512 it needs 2.4 Go VRAM on a total of 4 Go for my card, and 768x768 is 2.25 times more pixels than 512*512, so it won't run in my case. It is strange, because sometimes, if I let f32 type, it crashes with an explicit message : out of memory, with the amount it is trying to put on the GPU

[stduhpf]

Btw, I think SD2.1 support is broken (unrelated to Vulkan). I don't get black images like you do, but still very bad results. (see here #122 (comment))