Common Parameters

The following input parameters are common to most ALPS applications.

Lattice definition

ALPS applications on lattices specify the lattice with the following three parameters (see Lattice Definitions for how the lattice library itself is built):

Parameter	Default	Meaning
LATTICE_LIBRARY	lattices.xml	path to a file containing lattice descriptions
LATTICE		name of the lattice, specified by dimensionality, extent and unit cell
GRAPH		as an alternative to LATTICE, a specific arbitrary graph defined in the lattice library can be referenced directly

In addition, the lattice description can require further parameters (e.g. L or W) as specified in the lattice description file.

Model definition

ALPS quantum lattice models can be specified using the following parameters (see ALPS Model Definitions for how the model library itself is built):

Parameter	Default	Meaning
MODEL_LIBRARY	models.xml	path to a file containing model descriptions
MODEL		name of the model (for example “spin” or “boson”)

The model description can also require further parameters (e.g. S=1/2 or S=1, h=0.5 for spin models, t=1.5 or mu=0.5 for boson models) as specified in the model description file.

Parameters for finite temperature simulations

Parameter	Meaning
T	the temperature
BETA	inverse of temperature, used instead of T if T is not given

Additional parameters for Monte Carlo simulations

Parameter	Default	Meaning
SEED	0	the random number seed for this run. It is incremented by one each time a new run is created for the same task, so that repeated runs don’t reuse the same seed.
RNG	“mt19937”	the pseudo-random number generator to use. Allowed values are “lagged_fibonacci607” and “mt19937”.
WORK_FACTOR	1	a multiplier applied to this simulation’s estimated workload when the scheduler load-balances multiple tasks against each other.
SWEEPS		number of Monte Carlo steps (after thermalization)
THERMALIZATION		number of Monte Carlo sweeps for thermalization

These are parameters set in the parameter file itself. When running from the command line, the scheduler also accepts a separate set of runtime flags — such as --time-limit, --checkpoint-time, --Tmin/--Tmax, and --mpi/--Nmin/--Nmax for parallel runs — passed directly to the program rather than written into the parameter file; see Using the command line for the full list.

Additional parameters for exact diagonalization

These parameters are specific to the sparsediag and fulldiag applications:

Parameter	Default	Meaning
CONSERVED_QUANTUMNUMBERS		specifies conserved global quantum numbers, used to split the computation into smaller computations for the different sectors. If more than one quantum number is conserved, they are listed in double quotes and separated by commas, as in CONSERVED_QUANTUMNUMBERS=“N,Sz”
N_total, Sz_total, …		fixes the corresponding quantum number to a specific value, provided a `<CONSTRAINT>` for it is defined in the model (see Lattice Basis). Such a constraint is applied only when the parameter is given a value and the quantum number is also listed in CONSERVED_QUANTUMNUMBERS.
TRANSLATION_SYMMETRY	true	fulldiag and sparsediag exploit translational symmetry and classify eigenstates by their momentum quantum numbers when possible. This symmetry reduction can be switched off with TRANSLATION_SYMMETRY=false.
TOTAL_MOMENTUM		fixes the value of the total momentum. Further explanations can be found below.
MEASURE_ENERGY	false	fulldiag and sparsediag do not store any information on eigenstates by default unless measurements are explicitly specified. The energy can always be computed for any eigenstate, however; set MEASURE_ENERGY=true to include it in the output even when no other measurements are requested.

Note: Instead of true and false, you can also specify 1 and 0, respectively.

If the lattice supports translation symmetries, you can specify the total momentum quantum numbers, but you should be quite careful in doing so. TOTAL_MOMENTUM takes the momentum quantum numbers as a vector, i.e. a space-separated list of numbers. Typically, each momentum quantum number $k_i$ will be of the form

$k_i = 2\pi n_i/L_i$ ,

where $n_i$ is an integer and $L_i$ the linear extent in the corresponding direction. It is possible to specify a symbolic number such as 2Pi/5 if you put the values in quotation marks, e.g. TOTAL_MOMENTUM=“2Pi/5 0”.

Warning: An illegal value of TOTAL_MOMENTUM may lead to incorrect results without any further error message.

For how the LATTICE/LATTICE_LIBRARY parameters relate to the lattice library, see Lattice Definitions. For how the MODEL/MODEL_LIBRARY parameters relate to the model library, see ALPS Model Definitions. For the other ALPS documentation sections, see the General Introduction.

ALPS Custom Measurement