The NVIDIA RTX A4000, with its 16GB of GDDR6 VRAM, falls short of the 24GB VRAM requirement for the FLUX.1 Dev model when using FP16 precision. This means the entire model cannot be loaded onto the GPU simultaneously, leading to a compatibility failure. The A4000's memory bandwidth of 0.45 TB/s, while respectable, would also become a bottleneck if workarounds like offloading layers to system RAM were attempted, severely impacting performance. Even if the model could be forced to run, the limited VRAM would necessitate extremely small batch sizes, resulting in unacceptably low throughput.
Given the VRAM limitations, running FLUX.1 Dev on the RTX A4000 in FP16 is impractical. Consider exploring quantization techniques such as 8-bit or even 4-bit quantization to reduce the model's memory footprint. Alternatively, you could investigate using a different model with a smaller parameter size that fits within the A4000's VRAM. If feasible, upgrading to a GPU with at least 24GB of VRAM is the most straightforward solution for running FLUX.1 Dev without significant performance compromises.