Structure(cell, coded_species, pos, cutoff, descriptors) MemoryError: std::bad_alloc

I am trying to learn `sparse_gp_tutorial.ipynb`. When I increase the size of `training_size` and `validation_size`, an error occured.

```python
Structure(cell, coded_species, pos, cutoff, descriptors) 
    MemoryError: std::bad_alloc
```

I want to use it to deal with large system. How can I prevent the this error?