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by sillysaurusx
1215 days ago
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> On a single multi-GPUs server, even with the highest-end A100 80GB GPU, PyTorch can only launch ChatGPT based on small models like GPT-L (774M), due to the complexity and memory fragmentation of ChatGPT. Hence, multi-GPUs parallel scaling to 4 or 8 GPUs with PyTorch's DistributedDataParallel (DDP) results in limited performance gains. Where are these numbers coming from? An 80GB A100 GPU is certainly more than capable of hosting a 1.5B GPT. We were running 774M on rinky-dink cards back in 2019 for our inference purposes. I don’t understand how they went from talking about 175B params across 32 cards to 774M on one card. 175B divided by 32 is 5.4B. In fact, I’m not sure what they’re saying in general. They seem to be confusing data parallelism with model parallelism with memory fragmentation, while namedropping a bunch of training techniques. The hard part of ChatGPT isn’t the size. It’s the training process. It took a small army of contractors rating outputs as good or bad. Once that dataset gets replicated, we can start talking about size. Hopefully LAION will deliver. |
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>I don’t understand how they went from talking about 175B params across 32 cards to 774M on one card. 175B divided by 32 is 5.4B.
They claim 774M is the size of GPT-L which if run in conjunction with their RLHF would require 80GB A100 GPU to train (using their RLHF PyTorch implementation). They additionally claim that training GPT-3(175B params) plus RLHF would need 64 * 80gb = 5120gb of memory if using PyTorch implementation of RLHF or 32 * 80gb = 2560gb if going Colossal AI route.
To be honest, these numbers do look to me to be a bit of a cheesy ad for their product but hey they need to put food on their table too. I'm not sure if the dataset would be such a huge problem otherwise Britannica would still be ahead of Wikipedia. Given an army of volunteers willing to produce it OpenAI brigade of contractors has no chance.