implement multi-farm support in pywake_api

[kilojoules]

No description provided.

[bjarketol]

Hi @kilojoules,

I did a quick agent-based review. It found a few things.

High

• Per-farm AEP normalization mismatch — wifa/pywake_api.py:1040-1043, 1252-1254. For time-series cases, aep_per_turbine is computed with normalize_probabilities=True while total AEP uses normalize_probabilities=False. Multi-farm per-farm AEP is derived from aep_per_turbine, so it is on a different basis than total AEP. Fix: use the same normalization (False) for per-turbine AEP in time-series, then slice/sum per farm.

• Turbine deduplication by name only — wifa/pywake_api.py:285-293 (_build_multifarm_turbines). Two farms whose turbine YAMLs share a name (e.g. IEA-15MW) but differ in power curve/geometry are silently merged into the first farm's spec — wrong physics, no warning. Fix: dedupe by structural fingerprint, or raise when distinct specs share a name. At minimum warn on reuse.

Medium

• hub_heights collision across farms — wifa/pywake_api.py:97-100, 294, 1234. Single-type farms always key hub_heights with local "0"; hub_heights.update(hh) overwrites prior farms. Distinct hub heights are lost, breaking height-dependent site interpolation / FUGA setup. Fix: key by global turbine-type index (or farm-scoped key) and derive first_hh from merged global turbine objects.

• generate_outputs still receives a list in multi-farm path — wifa/pywake_api.py:~1249. generate_outputs(sim_results, system_dat, ...) was written for a single-farm dict; in the multi-farm branch system_dat["wind_farm"] is a list. Either crashes iterating farm_dat["layouts"] or silently writes only farm 0's artifacts. The new test only checks the return value. Fix: teach generate_outputs to handle a farm list (per-farm outputs), or branch/skip and document the gap. Extend the test to assert output-dir contents.

• farm_dat = farms[0] as a single-farm stand-in — wifa/pywake_api.py:~1218. Inline comment admits "assumes shared turbine spec across farms." Any downstream code reading farm_dat (e.g. rd lookup, layout-derived state) silently uses farm 0 only — defeating the point of multi-farm. Fix: refactor downstream usages to operate per-farm, or assert single-turbine-type in the multi-farm path. Don't paper over with a comment.

• Flaky wall-clock assertion — tests/test_pywake.py:~516 (test_pywake_multifarm_runs_fast). assert elapsed < 10.0 is flaky on shared CI and doesn't validate correctness. Fix: drop the timing assertion (or move to an opt-in benchmark) and rename the test to reflect what it verifies (per-farm AEP + wake interaction).

Low

• Unused _type_names — wifa/pywake_api.py:~284. Unpacked from _build_farm_turbine_list but never used; the type-name → global-index map is rebuilt from wt.name(), inconsistent with the per-farm "0"-style keys. Fix: remove the unused return, or use _type_names consistently.

• layouts shape assumption — wifa/pywake_api.py:~136 (_build_farm_turbine_list). The multi-type branch indexes farm_dat["layouts"][0]["turbine_types"] while the single-type branch handles both list and dict forms; a multi-type config with dict-form layouts crashes with an opaque error. Fix: normalize layouts to a list once at the top of the helper.

[SchmJo]

is this only for pywake? can we setup a new example case, such that I can also adopt foxes to read multiple farms from windio? Thanks