Use einsum on ADF calculator

[SamTov]

What feature would you like to see added? Currently it is not possible for us to always use einsum in the ADF computation. Rather we allow the user to select tf.function which will use considerable more memory but is much faster. Einsum would likely improve the speed further. Once we have access to more intelligent memory management, we should allow for internal selection of the einsum procedure to optimized computation time.

Describe how this feature would improve the code It would make it much faster.

Describe how this feature would work/possible implementations We would need to check that the machine can handle the memory load and if so, use einsum. We must keep in mind that some monitoring may be necessary to ensure other processes don't disrupt it, hence the necessity for intelligent memory management.