Migrating to 0.4¶

Polarism 0.4 reworks result output. Simulation numerics are unchanged; a run with the same configuration produces the same fields as in 0.3.

Renamed result datasets¶

Saved result names are now ASCII. Plots and movie titles keep the old text as display labels.

0.3 name	0.4 name
`\|ψ\|²`	`density`
`N(t)`	`norm`
`Pump`	`pump`

Code that opens HDF5 files directly must use the new paths, for example fields/density instead of fields/|ψ|², and NPY keys such as field_density. The simplest migration is to read through polarism.load_results, which also opens 0.3 files and maps their names:

import polarism as ps

with ps.load_results(run_dir) as result:
    density = result.fields["density"][:]

cfg.result.animation_fields still accepts the 0.3 names with a DeprecationWarning.

Static pump¶

A pump that does not change in time is stored once as static/pump (HDF5) or static_pump.npy (NPY) instead of one copy per frame. Pulsed pumps and pumps with a positive delay are still stored per frame under fields/pump. result.static["pump"] and result.fields["pump"] distinguish the two cases.

Compression¶

HDF5 output is uncompressed by default (0.3 used gzip level 4), and NPY batches use numpy.savez instead of numpy.savez_compressed. Files are larger, but writing is several times faster. Set cfg.result.compression = "lzf" or "gzip" to compress.

File metadata¶

HDF5 files carry format_version = 2 and polarism_version root attributes, grid/x and grid/y coordinates, and label/units dataset attributes. NPY runs write metadata.json, grid_x.npy and grid_y.npy.

Scalar result nodes¶

For scalar nodes (is_field=False), storage now records the value returned by compute_fn; reduce_dim_fn is applied only for CPU visitors such as the live view. Built-in nodes are unaffected. A custom node whose reduce_dim_fn does more than convert the value should move that computation into compute_fn.

Storage backends¶

Built-in backends are created through the storage registry with the constructor StorageClass(output_dir, batch_size, config, x, y) and receive host arrays on a background thread. Subclasses of BaseStorage must implement write_static(name, field) in addition to dump_batch and finalize.

New options¶

Option	Purpose
`result.formats`	output formats, including plugin formats
`result.observables`	extra result nodes from observable plugins
`result.compression`, `result.compression_level`	HDF5 compression
`result.save_psi`	store the complex condensate field
`checkpoint.every_steps`, `checkpoint.path`, `checkpoint.resume_from`, `checkpoint.on_signal`	checkpoint and restart