# 4.7. Known limitations of using GPUs

If you use DeePMD-kit in a GPU environment, the acceptable value range of some variables is additionally restricted compared to the CPU environment due to the software’s GPU implementations:

1. The number of atom types of a given system must be less than 128.

2. The maximum distance between an atom and its neighbors must be less than 128. It can be controlled by setting the rcut value of training parameters.

3. Theoretically, the maximum number of atoms that a single GPU can accept is about 10,000,000. However, this value is limited by the GPU memory size currently, usually within 1000,000 atoms even in the model compression mode.

4. The total sel value of training parameters(in model/descriptor section) must be less than 4096.

5. The size of the last layer of the embedding net must be less than 1024 during the model compression process.