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POC spinning off a process to compute parallactic angles #266

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POC spinning off a process to compute parallactic angles #266

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31 changes: 21 additions & 10 deletions africanus/rime/parangles_casa.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
# -*- coding: utf-8 -*-

import threading
from multiprocessing import Process, Queue

import numpy as np

Expand All @@ -16,23 +16,33 @@
casa_import_error = None
have_casa_parangles = True

# Create thread local storage for the measures server
_thread_local = threading.local()


@requires_optional('pyrap.measures', 'pyrap.quanta', casa_import_error)
def casa_parallactic_angles(times, antenna_positions, field_centre,
zenith_frame='AZEL'):

q = Queue()
p = Process(
target=_casa_parallactic_angles,
args=(times, antenna_positions, field_centre, zenith_frame, q)
)

p.start()
parangles = q.get()
p.join()

return parangles


@requires_optional('pyrap.measures', 'pyrap.quanta', casa_import_error)
def _casa_parallactic_angles(times, antenna_positions, field_centre,
zenith_frame, q):
"""
Computes parallactic angles per timestep for the given
reference antenna position and field centre.
"""

try:
meas_serv = _thread_local.meas_serv
except AttributeError:
# Create a measures server
_thread_local.meas_serv = meas_serv = pyrap.measures.measures()
meas_serv = pyrap.measures.measures()

# Create direction measure for the zenith
zenith = meas_serv.direction(zenith_frame, '0deg', '90deg')
Expand All @@ -47,7 +57,7 @@ def casa_parallactic_angles(times, antenna_positions, field_centre,
fc_rad = meas_serv.direction('J2000', *(pq.quantity(f, 'rad')
for f in field_centre))

return np.asarray([
q.put(np.asarray([
# Set current time as the reference frame
meas_serv.do_frame(meas_serv.epoch("UTC", pq.quantity(t, "s")))
and
Expand All @@ -58,3 +68,4 @@ def casa_parallactic_angles(times, antenna_positions, field_centre,
for rp in reference_positions
]
for t in times])
)