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name: dqmc-advanced description: Advanced DQMC features including unequal-time measurements, analytic continuation, and queue system internals. Use when enabling dynamical correlations, performing MaxEnt continuation, or understanding HDF5 data structure.

Advanced Topics

Unequal-Time Measurements

Enable by setting period_uneqlt > 0 during file generation:

Copydqmc-util gen period_uneqlt=8 ...

Required for:

• nnrw0, zzrw0 - Zero-frequency susceptibilities
• dwq0t - D-wave pair susceptibility
• Any time-dependent correlation functions

Note: Unequal-time measurements significantly increase runtime and memory usage.

Analytic Continuation

Use maximum entropy for continuing imaginary-time data to real frequencies:

Copyfrom dqmc_util import maxent

# Solve G = K A given:
# - G: binned data, shape (nbin, ntau)
# - K: kernel, shape (ntau, nw)
# - m: default model, shape (nw,)
A_omega = maxent.calc_A(G, K, m)

HDF5 File Structure

Copy/metadata/     # Model info (mu, Nx, Ny, beta)
/params/       # Simulation parameters, precomputed matrices
/state/        # RNG state, sweep number, aux field config
/meas_eqlt/    # Equal-time measurements (n_sample, sign, den, ...)
/meas_uneqlt/  # Unequal-time measurements (optional)

Queue System Internals

The sharded queue uses:

• 128 shards to avoid lock contention on distributed filesystems
• Atomic rename() operations for task claiming
• Symlinks moved: todo/ -> running/ -> done/
• Checkpointed jobs returned to todo/ for resumption