dqmc-generate

name	dqmc-generate
description	Create HDF5 simulation files for DQMC with specified physical parameters. Use when setting up new simulations, specifying lattice size, interaction strength U, chemical potential mu, temperature (via dt and L), or number of Monte Carlo sweeps.

Generate Simulation Files

Inputs

Input	Required	Default	Description
Nx, Ny	No	8	Lattice dimensions
U	No	6.0	On-site interaction strength
mu	No	0.0	Chemical potential
tp	No	0.0	Next-nearest neighbor hopping
dt	No	0.1	Imaginary time step
L	No	40	Number of time slices (beta = L*dt)
n_sweep_warm	No	200	Warmup sweeps
n_sweep_meas	No	2000	Measurement sweeps
Nfiles	No	1	Number of independent bins
prefix	No	sim	Output path prefix
period_uneqlt	No	0	Unequal-time period (0=disabled)

Outputs

• {prefix}_0.h5, {prefix}_1.h5, ... - HDF5 simulation files
• {prefix}.h5.params - common params HDF5 file

Procedure

Option A: CLI (simple cases)

dqmc-util gen Nx=6 Ny=6 U=4.0 mu=0.0 dt=0.1 L=50 Nfiles=4 prefix=data/run/bin

Option B: Python (parameter scans)

from dqmc_util import gen_1band_hub

gen_1band_hub.create_batch(
    prefix="data/run/bin", Nfiles=4,
    Nx=6, Ny=6, U=4.0, mu=0.0, tp=0.0, dt=0.1, L=50
)

Choosing dt and L for a target temperature T:

import numpy as np
T = 0.25  # target temperature
U = 4.0
beta = 1.0 / T
dt = min((0.05/U)**0.5, beta / 10)  # Trotter error constraint
L = int(np.ceil(beta / dt / 5) * 5)  # L must be divisible by n_matmul and period_eqlt (defaults: 5)
dt = beta / L  # recalculate exact dt

Validation

• Files created: ls {prefix}_*.h5 {prefix}.h5.params
• Trotter error check: U * dt^2 <= 0.05

Failure Modes

Symptom	Cause	Recovery
"File exists" error	Previous files not cleaned	Remove old files or use overwrite=1 argument
ValueError: L must be divisible ...	L must be multiple of n_matmul and period_eqlt	Adjust value of L and dt, keeping their product (beta) constant

Do Not

• Overwrite existing simulation files without confirmation
• Ignore the Trotter error bound (U * dt^2 <= 0.05)