Calculation Configurations#

Time Evolution Algorithms

class renormalizer.utils.configs.CompressConfig(criteria: Union[CompressCriteria, str] = CompressCriteria.threshold, threshold: float = 0.001, max_bonddim: int = 32, vmethod: str = '2site', vprocedure=None, vrtol=1e-05, vguess_m=(5, 5), dump_matrix_size=inf, dump_matrix_dir='./', ofs: Optional[OFS] = None, ofs_swap_jw: bool = False)[source]#

Bases: object

MPS/MPO Compress Configuration.

Parameters:

criteria (CompressCriteria, optional) – The criteria for compression. Default is CompressCriteria.threshold.
threshold (float, optional) – The threshold to keep states if criteria is set to CompressCriteria.threshold or CompressCriteria.both. Default is \(10^{-3}\).
max_bonddim (int, optional) – Maximum bond dimension M under various bond dimension distributions. Default is 32.
vmethod (str, optional) –
The algorithm used in variational compression. The default is 2site.
- 1site: optimize one site at a time during sweep.
- 2site: optimize two site at a time during sweep.
Note

It is recommended to use the 2site algorithm in variational optimization, though 1site algorithm is much cheaper. The reason is that 1site algorithm is easy to stuck into local minima while 2site algorithm is more robust. For complicated Hamiltonian, the problem is severer. The renormalized basis selection rule used here to partly solve the local minimal problem is according to Chan. J. Chem. Phys. 2004, 120, 3172. For efficiency, you could use 2site algorithm for several sweeps and then switch to 1site algorithm to converge the final mps.

vprocedure (list, optional) –

The procedure to do variational compression. In the sublist, the first element is a CompressConfig, which controls the compression in each sweep. For backward compatibility, it can also be an int, which indicates CompressCriteria.fixed with the int as the max_bonddim. The Default is

if vmethod == "1site":
    vprocedure = [[max_bonddim,1.0],[max_bonddim,0.7],
                  [max_bonddim,0.5],[max_bonddim,0.3],
                  [max_bonddim,0.1]] + [[max_bonddim,0],]*10
else:
    vprocedure = [[max_bonddim,0.5],[max_bonddim,0.3],
                  [max_bonddim,0.1]] + [[max_bonddim,0],]*10

vrtol (float, optional) – The threshold of convergence in variational compression. Default is \(10^{-5}\).
vguess_m (tuple(int), optional) – The bond dimension of compressed_mpo and compressed_mps to construct the initial guess compressed_mpo @ compressed_mps in MatrixProduct.variational_compress. The default is (5,5).
dump_matrix_size (int or float, optional) –
The total bytes threshold for dumping matrix into disks. Every local site matrix in the MPS/MPO with a size larger than the specified size will be moved from memory to the disk at dump_matrix_dir. The matrix will be moved back to memory upon access. The dumped matrices on the disks will be removed once the MPS/MPO is garbage-collected.

Note

If dump_matrix_size is set and the program exits abnormally, it is possible that the dumped matrices are not deleted automatically. A common case when this can happen is that the program is killed by a signal. In such cases it is recommended to check and clean dump_matrix_dir after the exit of the program since the dumped matrices may take a lot of disk space.
dump_matrix_dir (str, optional) – The directory to dump matrix when matrix is larger than dump_matrix_size.
ofs (OFS, optional) – Whether optimize the DOF ordering by OFS. The default value is None which means does not perform OFS.
ofs_swap_jw (bool, optional) – Whether swap the Jordan-Wigner transformation ordering when OFS is enabled. Set to True for and only for ab initio Hamiltonian constructed by the experimental renormalizer.model.h_qc.qc_model. Default is False.