refactor template histogram creation to accept list of tasks

example.py

@@ -17,7 +17,20 @@
     cabinetry.configuration.print_overview(config)
 
     # create template histograms
-    cabinetry.templates.build(config, method="uproot")
+    from dask.distributed import Client, LocalCluster, wait
+
+    def produce_single_template(template):
+        cabinetry.templates.build(config, template_list=[template])
+
+    template_list = cabinetry.route.required_templates(config)
+
+    with LocalCluster(n_workers=2) as cluster:
+        client = Client(cluster)
+        wait(client.map(produce_single_template, template_list))
+
+    # cabinetry.templates.build(config, template_list=template_list)
+
+    raise SystemExit
 
     # perform histogram post-processing
     cabinetry.templates.postprocess(config)

src/cabinetry/route.py

@@ -2,7 +2,7 @@
 
 import fnmatch
 import logging
-from typing import Any, Callable, Dict, List, Literal, Optional
+from typing import Any, Callable, Dict, List, Literal, Optional, Tuple
 
 import boost_histogram as bh
 
@@ -38,6 +38,12 @@
 # (which returns a histogram) into a function that returns None
 WrapperFunc = Callable[[UserTemplateFunc], ProcessorFunc]
 
+# type of tuple capturing all relevant information to obtain a template histogram
+# this includes region, sample, systematic and template (up/down)
+TemplateHistogramInformation = Tuple[
+    Dict[str, Any], Dict[str, Any], Dict[str, Any], Optional[Literal["Up", "Down"]]
+]
+
 
 class Router:
     """Holds user-defined processing functions and matches functions to templates.
@@ -257,33 +263,18 @@ def _find_template_builder_match(
         return None
 
 
-def apply_to_all_templates(
-    config: Dict[str, Any],
-    default_func: ProcessorFunc,
-    *,
-    match_func: Optional[MatchFunc] = None,
-) -> None:
-    """Applies the supplied function ``default_func`` to all templates.
-
-    The templates are specified by the configuration file. The function takes four
-    arguments in this order:
-
-    - the dict specifying region information
-    - the dict specifying sample information
-    - the dict specifying systematic information
-    - the template being considered: "Up", "Down", or None for the nominal template
-
-    In addition it is possible to specify a function that returns custom overrides. If
-    one is found for a given template, it is used instead of the default.
+def required_templates(config: Dict[str, Any]) -> List[TemplateHistogramInformation]:
+    """Returns relevant information needed to produce all required template histograms.
 
     Args:
         config (Dict[str, Any]): cabinetry configuration
-        default_func (ProcessorFunc): function to be called for every template by
-            default
-        match_func: (Optional[MatchFunc], optional): function that returns user-defined
-            functions to override the call to ``default_func``, defaults to None (then
-            it is not used)
+
+    Returns:
+        List[TemplateHistogramInformation]: list of relevant information for each
+        template histogram
     """
+    all_templates = []
+
     for region in config["Regions"]:
         log.debug(f"  in region {region['Name']}")
 
@@ -321,22 +312,52 @@ def apply_to_all_templates(
                         f"{' ' + template if template is not None else ''}"
                     )
 
-                    func_override = None
-                    if match_func is not None:
-                        # check whether a user-defined function was registered that
-                        # matches this region-sample-systematic-template
-                        systematic_name = (
-                            systematic["Name"] if template is not None else ""
-                        )
-                        func_override = match_func(
-                            region["Name"], sample["Name"], systematic_name, template
-                        )
-                    if func_override is not None:
-                        # call the user-defined function
-                        log.debug(
-                            f"executing user-defined override {func_override.__name__}"
-                        )
-                        func_override(region, sample, systematic, template)
-                    else:
-                        # call the provided default function
-                        default_func(region, sample, systematic, template)
+                    all_templates.append((region, sample, systematic, template))
+
+    return all_templates
+
+
+def apply_to_templates(
+    default_func: ProcessorFunc,  # BREAKING API CHANGE
+    template_list: List[TemplateHistogramInformation],
+    *,
+    match_func: Optional[MatchFunc] = None,
+) -> None:
+    """Applies the supplied function ``default_func`` to all templates.
+
+    The templates are specified by the configuration file. The function takes four
+    arguments in this order:
+
+    - the dict specifying region information
+    - the dict specifying sample information
+    - the dict specifying systematic information
+    - the template being considered: "Up", "Down", or None for the nominal template
+
+    In addition it is possible to specify a function that returns custom overrides. If
+    one is found for a given template, it is used instead of the default.
+
+    Args:
+        default_func (ProcessorFunc): function to be called for every template by
+            default
+        template_list (List[TemplateHistogramInformation]): list of template information
+            to apply function to
+        match_func: (Optional[MatchFunc], optional): function that returns user-defined
+            functions to override the call to ``default_func``, defaults to None (then
+            it is not used)
+    """
+    for region, sample, systematic, template in template_list:
+        func_override = None
+        if match_func is not None:
+            # check whether a user-defined function was registered that
+            # matches this region-sample-systematic-template
+            systematic_name = systematic["Name"] if template is not None else ""
+            func_override = match_func(
+                region["Name"], sample["Name"], systematic_name, template
+            )
+        if func_override is not None:
+            # call the user-defined function
+            log.debug(f"executing user-defined override {func_override.__name__}")
+            func_override(region, sample, systematic, template)
+        else:
+            # call the provided default function
+            default_func(region, sample, systematic, template)

src/cabinetry/templates/__init__.py

@@ -2,7 +2,7 @@
 
 import logging
 import pathlib
-from typing import Any, Dict, Optional
+from typing import Any, Dict, List, Optional
 
 from cabinetry import route
 from cabinetry.templates import builder
@@ -18,6 +18,7 @@ def build(
     *,
     method: str = "uproot",
     router: Optional[route.Router] = None,
+    template_list: Optional[List[route.TemplateHistogramInformation]] = None,
 ) -> None:
     """Produces all required histograms specified by the configuration file.
 
@@ -31,6 +32,8 @@ def build(
             "uproot"
         router (Optional[route.Router], optional): instance of cabinetry.route.Router
             that contains user-defined overrides, defaults to None
+        template_list (Optional[List[route.TemplateHistogramInformation]]): list of
+            information for templates to process, defaults to None (all templates)
     """
     # create an instance of the class doing the template building
     histogram_folder = pathlib.Path(config["General"]["HistogramFolder"])
@@ -44,12 +47,21 @@ def build(
         # get a function that can be queried to return a user-defined template builder
         match_func = router._find_template_builder_match
 
-    route.apply_to_all_templates(
-        config, template_builder._create_histogram, match_func=match_func
+    # get list of required templates to process if not provided already
+    if template_list is None:
+        template_list = route.required_templates(config)
+
+    route.apply_to_templates(
+        template_builder._create_histogram, template_list, match_func=match_func
     )
 
 
-def collect(config: Dict[str, Any], *, method: str = "uproot") -> None:
+def collect(
+    config: Dict[str, Any],
+    *,
+    method: str = "uproot",
+    template_list: Optional[List[route.TemplateHistogramInformation]] = None,
+) -> None:
     """Collects all required histograms specified by the configuration file.
 
     Histograms must already exist, and this collects and saves them in the format used
@@ -60,6 +72,8 @@ def collect(config: Dict[str, Any], *, method: str = "uproot") -> None:
         config (Dict[str, Any]): cabinetry configuration
         method (str, optional): backend to use for histogram production, defaults to
             "uproot"
+        template_list (Optional[List[route.TemplateHistogramInformation]]): list of
+            information for templates to process, defaults to None (all templates)
     """
     histogram_folder = pathlib.Path(config["General"]["HistogramFolder"])
     general_path = config["General"]["InputPath"]
@@ -71,15 +85,30 @@ def collect(config: Dict[str, Any], *, method: str = "uproot") -> None:
     processor = collector._collector(
         histogram_folder, general_path, variation_path, method
     )
-    route.apply_to_all_templates(config, processor)
 
+    # get list of required templates to process if not provided already
+    if template_list is None:
+        template_list = route.required_templates(config)
+
+    route.apply_to_templates(processor, template_list)
 
-def postprocess(config: Dict[str, Any]) -> None:
+
+def postprocess(
+    config: Dict[str, Any],
+    template_list: Optional[List[route.TemplateHistogramInformation]] = None,
+) -> None:
     """Applies postprocessing to all histograms.
 
     Args:
         config (Dict[str, Any]): cabinetry configuration
+        template_list (Optional[List[route.TemplateHistogramInformation]]): list of
+            information for templates to process, defaults to None (all templates)
     """
     histogram_folder = pathlib.Path(config["General"]["HistogramFolder"])
     processor = postprocessor._postprocessor(histogram_folder)
-    route.apply_to_all_templates(config, processor)
+
+    # get list of required templates to process if not provided already
+    if template_list is None:
+        template_list = route.required_templates(config)
+
+    route.apply_to_templates(processor, template_list)