JP-3678: Ensure C extension works with multiprocessing (#268)

* Updating the use of the C extension, making sure the selection of the C extension gets properly set for multiprocessing.

* Updating the change log.

* Changing some logging statements from 'info' to 'debug'.

CHANGES.rst

@@ -14,7 +14,13 @@ Changes to API
 Bug Fixes
 ---------
 
-- 
+
+ramp_fitting
+~~~~~~~~~~~~
+
+- When OLS_C was selected as the ramp fitting algorithm with multiprocessing, the C
+  extension was not called.  The old python code was called.  This bug has been fixed,
+  so the C extension is properly run when selecting multiprocessing. [#268]
 
 1.7.2 (2024-06-12)
 ==================

src/stcal/ramp_fitting/ols_fit.py

@@ -75,6 +75,7 @@ def ols_ramp_fit_multi(ramp_data, buffsize, save_opt, readnoise_2d, gain_2d, wei
     nrows = ramp_data.data.shape[2]
     num_available_cores = cpu_count()
     number_slices = utils.compute_num_slices(max_cores, nrows, num_available_cores)
+    log.info(f"Number of multiprocessing slices: {number_slices}")
 
     # For MIRI datasets having >1 group, if all pixels in the final group are
     #   flagged as DO_NOT_USE, resize the input model arrays to exclude the
@@ -574,6 +575,8 @@ def slice_ramp_data(ramp_data, start_row, nrows):
     ramp_data_slice.start_row = start_row
     ramp_data_slice.num_rows = nrows
 
+    ramp_data_slice.run_c_code = ramp_data.run_c_code
+
     return ramp_data_slice
 
 
@@ -661,19 +664,20 @@ def ols_ramp_fit_single(ramp_data, buffsize, save_opt, readnoise_2d, gain_2d, we
     opt_info : tuple
         The tuple of computed optional results arrays for fitting.
     """
-    # use_c = False
-    # use_c = True  # XXX Change to default as False
-    use_c = ramp_data.dbg_run_c_code
+    use_c = ramp_data.run_c_code
     if use_c:
         c_start = time.time()
 
         ramp_data, gain_2d, readnoise_2d, bswap = endianness_handler(ramp_data, gain_2d, readnoise_2d)
 
         if ramp_data.drop_frames1 is None:
             ramp_data.drop_frames1 = 0
+        log.debug("Entering C extension")
         image_info, integ_info, opt_info = ols_slope_fitter(
                 ramp_data, gain_2d, readnoise_2d, weighting, save_opt)
 
+        log.debug("Returning from C extension")
+
         c_end = time.time()
 
         # Read noise is used after STCAL ramp fitting for the CHARGELOSS
@@ -694,8 +698,10 @@ def ols_ramp_fit_single(ramp_data, buffsize, save_opt, readnoise_2d, gain_2d, we
 
     p_start = time.time()
 
+    log.debug("Entering python code")
     image_info, integ_info, opt_info = ols_ramp_fit_single_python(
         ramp_data, buffsize, save_opt, readnoise_2d, gain_2d, weighting)
+    log.debug("Returning from python ")
 
     p_end = time.time()
     p_diff = p_end - p_start

src/stcal/ramp_fitting/ramp_fit.py

@@ -173,7 +173,7 @@ def ramp_fit(
     ramp_data = create_ramp_fit_class(model, dqflags, suppress_one_group)
 
     if algorithm.upper() == "OLS_C":
-        ramp_data.dbg_run_c_code = True
+        ramp_data.run_c_code = True
 
     return ramp_fit_data(
         ramp_data, buffsize, save_opt, readnoise_2d, gain_2d, algorithm, weighting, max_cores, dqflags

src/stcal/ramp_fitting/ramp_fit_class.py

@@ -40,7 +40,7 @@ def __init__(self):
         self.suppress_one_group_ramps = False
 
         # C code debugging switch.
-        self.dbg_run_c_code = False
+        self.run_c_code = False
 
         self.one_groups_locs = None  # One good group locations.
         self.one_groups_time = None  # Time to use for one good group ramps.