JP-3632: Change the Spec of Ramp Fitting to Select Algorithm (spacete…

…lescope#8503)

CHANGES.rst

@@ -124,6 +124,11 @@ ramp_fitting
   to use uint16 instead of uint8, in order to avoid potential
   overflow/wraparound problems. [#8377]
 
+- Changed the spec for ramp fitting that allows for selecting
+  the algorithm "OLS" to use the python implementation of ramp
+  fitting or "OLS_C" to use the C extension implementation of
+  ramp fitting. [#8503]
+
 resample
 --------
 

docs/jwst/ramp_fitting/arguments.rst

@@ -2,6 +2,11 @@ Arguments
 =========
 The ramp fitting step has the following optional arguments that can be set by the user:
 
+* ``--algorithm``: A string to select the desired algorithm.  The available
+  values are "OLS" to select the python implementation of the Ordinary
+  Least Squares algorithm and  "OLS_C" to select the C extension
+  implementation of OLS.  The algorithm defaults to "OLS".
+
 * ``--save_opt``: A True/False value that specifies whether to write
   the optional output product. Default is False.
 

jwst/ramp_fitting/ramp_fit_step.py

@@ -385,6 +385,7 @@ class RampFitStep(Step):
     class_alias = "ramp_fit"
 
     spec = """
+        algorithm = option('OLS', 'OLS_C', default='OLS') # Can be 'OLS_C' to select the C extension
         int_name = string(default='')
         save_opt = boolean(default=False) # Save optional output
         opt_name = string(default='')
@@ -399,8 +400,8 @@ class RampFitStep(Step):
     # As of 04/26/17, the only allowed algorithm is 'ols', and the
     #      only allowed weighting is 'optimal'.
 
-    algorithm = 'ols'      # Only algorithm allowed for Build 7.1
-#    algorithm = 'gls'       # 032520
+    # algorithm = 'ols'      # Only algorithm allowed for Build 7.1
+    # algorithm = 'gls'       # 032520
 
     weighting = 'optimal'  # Only weighting allowed for Build 7.1