feat: Bookkeep fixed parameters (#989)

* Add functionality into _ModelConfig to bookkeep fixed systematics (all parameters for a given systematic)
* Add fixed into tests for paramsets
* Add tests for fixed parameters

Author: kratsg

src/pyhf/modifiers/histosys.py

@@ -20,6 +20,7 @@ def required_parset(cls, sample_data, modifier_data):
             'is_shared': True,
             'inits': (0.0,),
             'bounds': ((-5.0, 5.0),),
+            'fixed': False,
             'auxdata': (0.0,),
         }
 

src/pyhf/modifiers/lumi.py

@@ -20,6 +20,7 @@ def required_parset(cls, sample_data, modifier_data):
             'op_code': cls.op_code,
             'inits': None,  # lumi
             'bounds': None,  # (0, 10*lumi)
+            'fixed': False,
             'auxdata': None,  # lumi
             'sigmas': None,  # lumi * lumirelerror
         }

src/pyhf/modifiers/normfactor.py

@@ -19,6 +19,7 @@ def required_parset(cls, sample_data, modifier_data):
             'is_shared': True,
             'inits': (1.0,),
             'bounds': ((0, 10),),
+            'fixed': False,
         }
 
 

src/pyhf/modifiers/normsys.py

@@ -20,6 +20,7 @@ def required_parset(cls, sample_data, modifier_data):
             'is_shared': True,
             'inits': (0.0,),
             'bounds': ((-5.0, 5.0),),
+            'fixed': False,
             'auxdata': (0.0,),
         }
 

src/pyhf/modifiers/shapefactor.py

@@ -19,6 +19,7 @@ def required_parset(cls, sample_data, modifier_data):
             'is_shared': True,
             'inits': (1.0,) * len(sample_data),
             'bounds': ((0.0, 10.0),) * len(sample_data),
+            'fixed': False,
         }
 
 

src/pyhf/modifiers/shapesys.py

@@ -27,6 +27,7 @@ def required_parset(cls, sample_data, modifier_data):
             'is_shared': False,
             'inits': (1.0,) * n_parameters,
             'bounds': ((1e-10, 10.0),) * n_parameters,
+            'fixed': False,
             # nb: auxdata/factors set by finalize. Set to non-numeric to crash
             # if we fail to set auxdata/factors correctly
             'auxdata': (None,) * n_parameters,

src/pyhf/modifiers/staterror.py

@@ -19,6 +19,7 @@ def required_parset(cls, sample_data, modifier_data):
             'is_shared': True,
             'inits': (1.0,) * len(sample_data),
             'bounds': ((1e-10, 10.0),) * len(sample_data),
+            'fixed': False,
             'auxdata': (1.0,) * len(sample_data),
         }
 

src/pyhf/parameters/paramsets.py

@@ -6,6 +6,7 @@ def __init__(self, **kwargs):
         self.n_parameters = kwargs.pop('n_parameters')
         self.suggested_init = kwargs.pop('inits')
         self.suggested_bounds = kwargs.pop('bounds')
+        self.fixed = kwargs.pop('fixed')
 
 
 class unconstrained(paramset):

src/pyhf/parameters/utils.py

@@ -12,6 +12,7 @@ def reduce_paramsets_requirements(paramsets_requirements, paramsets_user_configs
         'auxdata',
         'factors',
         'sigmas',
+        'fixed',
     ]
 
     # - process all defined paramsets
@@ -27,6 +28,7 @@ def reduce_paramsets_requirements(paramsets_requirements, paramsets_user_configs
         combined_paramset = {}
         for k in paramset_keys:
             for paramset_requirement in paramset_requirements:
+                # undefined: the modifier does not support configuring that property
                 v = paramset_requirement.get(k, 'undefined')
                 combined_paramset.setdefault(k, set([])).add(v)
 

src/pyhf/pdf.py

@@ -93,6 +93,7 @@ def _paramset_requirements_from_modelspec(spec, channel_nbins):
         paramset_type = paramset_requirements.get('paramset_type')
         paramset = paramset_type(**paramset_requirements)
         _sets[param_name] = paramset
+
     return _sets
 
 
@@ -229,8 +230,8 @@ def __init__(self, spec, **config_kwargs):
         )
 
         if config_kwargs:
-            raise KeyError(
-                f"""Unexpected keyword argument(s): '{"', '".join(config_kwargs.keys())}'"""
+            raise exceptions.Unsupported(
+                f"Unsupported options were passed in: {list(config_kwargs.keys())}."
             )
 
         self.par_map = {}
@@ -265,6 +266,31 @@ def par_slice(self, name):
     def param_set(self, name):
         return self.par_map[name]['paramset']
 
+    def suggested_fixed(self):
+        """
+        Identify the fixed parameters in the model.
+
+        Returns:
+            List: A list of booleans, ``True`` for fixed and ``False`` for not fixed.
+
+        Something like the following to build fixed_vals appropriately:
+
+        .. code:: python
+
+            fixed_pars = pdf.config.suggested_fixed()
+            inits = pdf.config.suggested_init()
+            fixed_vals = [
+                (index, init)
+                for index, (init, is_fixed) in enumerate(zip(inits, fixed_pars))
+                if is_fixed
+            ]
+        """
+        fixed = []
+        for name in self.par_order:
+            paramset = self.par_map[name]['paramset']
+            fixed = fixed + [paramset.fixed] * paramset.n_parameters
+        return fixed
+
     def set_poi(self, name):
         if name not in [x for x, _ in self.modifiers]:
             raise exceptions.InvalidModel(