netket.experimental.sampler.MetropolisLocalPt

class netket.experimental.sampler.MetropolisLocalPt

Bases:

Sampler acting on one local degree of freedom.

This sampler acts locally only on one local degree of freedom \(s_i\), and proposes a new state: \(s_1 \dots s^\prime_i \dots s_N\), where \(s^\prime_i \neq s_i\).

The transition probability associated to this sampler can be decomposed into two steps:

1. One of the site indices \(i = 1\dots N\) is chosen with uniform probability.

2. Among all the possible (\(m\)) values that \(s_i\) can take, one of them is chosen with uniform probability.

For example, in the case of spin \(1/2\) particles, \(m=2\) and the possible local values are \(s_i = -1,+1\). In this case then MetropolisLocal is equivalent to flipping a random spin.

In the case of bosons, with occupation numbers \(s_i = 0, 1, \dots n_{\mathrm{max}}\), MetropolisLocal would pick a random local occupation number uniformly between \(0\) and \(n_{\mathrm{max}}\).

Parameters:

• hilbert – The hilbert space to sample

• n_chains – The number of Markov Chain to be run in parallel on a single process.

• sweep_size – The number of exchanges that compose a single sweep. If None, sweep_size is equal to the number of degrees of freedom being sampled (the size of the input vector s to the machine).

• n_chains – The number of batches of the states to sample (default = 8)

• machine_pow – The power to which the machine should be exponentiated to generate the pdf (default = 2).

• dtype – The dtype of the states sampled (default = np.float32).