5 add fab build script

CONTRIBUTORS.md

@@ -1,7 +1,8 @@
 # Contributors
 
-| GitHub user     | Real Name       | Affiliation           | Date       |
-| --------------- | --------------- | --------------------- | ---------- |
-| james-bruten-mo | James Bruten    | Met Office            | 2025-12-09 |
-| trjr            | Todd Jones      | University of Reading | 2026-05-01 |
-| yaswant         | Yaswant Pradhan | Met Office            | 2026-07-17 |
+| GitHub user     | Real Name       | Affiliation                      | Date       |
+| --------------- | --------------- | -------------------------------- | ---------- |
+| james-bruten-mo | James Bruten    | Met Office                       | 2025-12-09 |
+| trjr            | Todd Jones      | University of Reading            | 2026-05-01 |
+| yaswant         | Yaswant Pradhan | Met Office                       | 2026-07-17 |
+| hiker           | Joerg Henrichs  | Bureau of Meteorology, Australia | 2026-07-30 |

fab/.gitignore

@@ -0,0 +1 @@
+fab-workspace

fab/README.md

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+# Fab Build Scripts for MONC
+
+This directory contains the files for building MONC with Fab.
+
+You need Fab version 2.2.0 (or later).
+
+## Building
+The build script is a Python script that relies on Fab.
+MONC can be compiled by providing the required
+command line options to the script.
+
+Please read the Fab documentation (esp the 
+[introduction to the Fab base class](https://metoffice.github.io/fab/fab_base/index.html)
+for details. See also the next section ('setup') if you need site-specific
+modifications.
+
+The actual build is defined by command line parameters to the
+``fab_monc.py`` script. Use the ``-h`` option to list all available
+options. Many options are inherited from the Fab base class, only
+MONC specific options are defined in ``fab_monc.py`` and are grouped
+at the end of the help output::
+
+    MONC configuration options:
+      --petsc               Enable the usage of PETSc. (default: False)
+      --casim               Enable the usage of CASIM. (default: False)
+      --casim-profile-dgs   Enable the usage of CASIM profile dgs. (default: False)
+      --socrates            Enable the usage of SOCRATES. (default: False)
+
+In the ``site_specific`` directory are various site-specific
+setups. The main one is called ``default``, and it contains setting
+for any compiler currently supported by Fab. But each site can
+modify the settings. Have a look at the existing configurations
+already contained in MONC, and check the
+[Fab documentation](https://metoffice.github.io/fab/fab_base/config.html)
+for a full explanation of the available options. 
+
+Specific for MONC, I have added a `NfConfig.py` class, which wraps
+the detection of NetCDF using the `nf-config` tools. This is a copy
+of the file used in LFRic_core. A site can overwrite the settings
+if e.g. `nf-config` is not available or not working properly.
+
+An example build can be done as follows::
+
+    ./fab_monc.py   --site nci --platform gadi --suite gnu  --profile debug
+
+The compilers are selected by specifying a suite (Fab supports out of
+the box ``gnu``, ``intel-classic``, ``intel-llvm``, ``nvidia`` and
+``cray``), and it will use the corresponding Fortran and C compiler.
+If MPI is enabled (which is the default), Fab will search for
+corresponding ``mpif90`` and ``mpicc`` compiler wrapper, and verify
+that they are indeed of the right suite. If you need to use say
+a different C compiler (e.g. use ``gcc`` in an otherwise Intel build),
+use the ``-cc`` command line option.
+
+Any Fab script also supports the ``--available-compilers`` flag, which
+just lists all compilers that Fab knows about that are available on the
+system. Example output (of a system that has ``gfortran`` and ``mpif90``
+as a wrapper for gfortran)::
+
+    ----- Available compiler and linkers -----
+    Gcc - gcc: gcc
+    Mpicc - mpicc-gcc: mpicc
+    Gfortran - gfortran: gfortran
+    Mpif90 - mpif90-gfortran: mpif90
+    Linker - linker-gcc: gcc
+    Linker - linker-gfortran: gfortran
+    Linker - linker-mpif90-gfortran: mpif90
+    Linker - linker-mpicc-gcc: mpicc
+
+The Fab workspace defaults to ``./fab-workspace``, but this can be
+changed using the ``--fab-workspace`` command line option.
+
+If the build finished successfully, the binary will be in the
+directory ``fab-workspace/monc-debug-gfortran/``, it is
+called ``monc_driver``. The actual directory name will depend on the
+options specified of course.
+
+## Setting up site-specific options
+If you need site-specific options (e.g. you want to change the
+default compiler flags used for your compiler), create
+a directory with the name of your site and platform under
+``site-specific``. Please check the existing
+[Fab documentation](https://metoffice.github.io/fab/fab_base/config.html)
+for examples on setting up options, or the existing
+site-specific setups under ``fab/site-specific``.

fab/fab_monc.py

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+#!/usr/bin/env python3
+##############################################################################
+# (c) Crown copyright Met Office. All rights reserved.
+# For further details please refer to the file COPYRIGHT
+# which you should have received as part of this distribution
+##############################################################################
+
+'''
+This module contains a Fab-based build script for the Unified Model.
+'''
+
+import argparse
+import logging
+from pathlib import Path
+from typing import cast, Iterable, List, Optional, Union
+
+from fab.fab_base.fab_base import FabBase
+from fab.api import (AddFlags, Category, Compiler, Exclude, find_source_files,
+                     grab_folder, Include, root_inc_files)
+
+# Since we don't have a proper python package, we cannot use __name__, so set
+# up an appropriate dotted name for logging:
+logger = logging.getLogger("monc.fab.fab_monc")
+
+
+class FabMonc(FabBase):
+    '''
+    A class to build MONC using Fab as base class.
+
+    :param str name: name of the build.
+    '''
+
+    def __init__(self, name):
+        super().__init__(name)
+        # We need to overwrite the name of the main program, it
+        # defaults to `monc`.
+        self.set_root_symbols("monc_driver")
+        # Store the root directory of MONC:
+        self._root = Path(__file__).resolve().parents[1]
+
+    def define_command_line_options(
+            self,
+            parser: Optional[argparse.ArgumentParser] = None
+            ) -> argparse.ArgumentParser:
+        '''
+        Adds the additionally required command line options for the UM.
+
+        :param Optional[argparse.ArgumentParser] parser: a pre-defined
+        argument parser. If not, a new instance will be created.
+
+        :returns: the argument parser with the UM specific options added.
+        '''
+
+        parser = super().define_command_line_options(parser)
+        parser = cast(argparse.ArgumentParser, parser)
+
+        monc_config = parser.add_argument_group("MONC configuration options")
+        monc_config.add_argument(
+            "--petsc", action="store_true", default=False,
+            help="Enable the usage of PETSc.")
+        monc_config.add_argument(
+            "--casim", action="store_true", default=False,
+            help="Enable the usage of CASIM.")
+        monc_config.add_argument(
+            "--casim-profile-dgs", action="store_true",
+            default=False, help="Enable the usage of CASIM profile dgs.")
+        monc_config.add_argument(
+            "--socrates", action="store_true", default=False,
+            help="Enable the usage of SOCRATES.")
+
+        return parser
+
+    def grab_files_step(self) -> None:
+        '''
+        Extracts all the required source files from the repositories.
+        It then sets the include path (since include files are not
+        copied into the build tree).
+
+        :raises RuntimeError: the expected `rose-meta/um-atmos` file
+            does not exist, indicating an invalid directory structure.
+        '''
+        for directory in ["components", "io", "misc", "model_core",
+                          "testcases"]:
+            grab_folder(self.config, self._root / directory,
+                        dst_label=directory)
+
+    def find_source_files_step(
+            self,
+            path_filters: Optional[Iterable[Union[Exclude, Include]]] = None
+            ):
+        '''
+        Finds all the UM sources files to analyse. If the tests are
+        being compiled, only search the tests directory.
+        '''
+        path_filters = [Exclude("model_core/test")]
+        if self.args.petsc:
+            # Exclude the stub if we are using PETSc
+            path_filters.append(Exclude("petsc_solver_stub.F90"))
+        else:
+            # No PETSc, ignore the solver (and use the stub)
+            path_filters.append(Exclude("petsc_solver.F90"))
+
+        if self.args.casim:
+            path_filters.append(Exclude("casim_stub.F90"))
+        else:
+            path_filters.append(Exclude("casim.F90"))
+
+        if self.args.casim_profile_dgs:
+            path_filters.append(Exclude("casim_profile_dgs_stub.F90"))
+        else:
+            path_filters.append(Exclude("casim_profile_dgs.F90"))
+
+        if self.args.socrates:
+            path_filters.append(Exclude("socrates_couple_stub.F90"))
+        else:
+            path_filters.append(Exclude("socrates_couple.F90"))
+
+        find_source_files(self.config,
+                          path_filters=path_filters)
+        root_inc_files(self.config, [".h", ".static"])
+
+    def define_preprocessor_flags_step(self) -> None:
+        '''
+        Defines the preprocessor flags.
+        '''
+        super().define_preprocessor_flags_step()
+
+        flags = ['-DU_ACTIVE', '-DV_ACTIVE', '-DW_ACTIVE',
+                 '-DENFORCE_THREAD_SAFETY', '-D__DARWIN',
+                 '-D_XOPEN_SOURCE=700',
+                 '-I$output',
+                 ]
+        if self.args.profile == "debug":
+            flags.append("-DDEBUG_MODE")
+
+        self.add_preprocessor_flags(flags)
+
+    def compile_fortran_step(
+            self,
+            common_flags: Optional[List[str]] = None,
+            path_flags: Optional[List[AddFlags]] = None
+            ) -> None:
+
+        fc = self.config.tool_box.get_tool(Category.FORTRAN_COMPILER)
+        fc = cast(Compiler, fc)
+        new_flags = []
+        if common_flags:
+            new_flags.extend(common_flags)
+
+        super().compile_fortran_step(common_flags=new_flags,
+                                     path_flags=path_flags)
+
+    def get_linker_flags(self) -> List[str]:
+        return ["netcdf"]
+
+
+# ==========================================================================
+if __name__ == "__main__":
+
+    # Initialise a top-level logger
+    logger = logging.getLogger('um')
+    logger.setLevel(logging.DEBUG)
+    handler = logging.StreamHandler()
+    formatter = logging.Formatter('%(levelname)s: %(name)s: %(message)s')
+    handler.setFormatter(formatter)
+    logger.addHandler(handler)
+
+    fab_monc = FabMonc("monc")
+    fab_monc.build()

fab/nf_config.py

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+##############################################################################
+# (c) Crown copyright Met Office. All rights reserved.
+# For further details please refer to the file COPYRIGHT
+# which you should have received as part of this distribution
+##############################################################################
+
+"""This file contains the class to interface with NetCDF's nf-config script.
+"""
+
+from typing import List
+
+from fab.tools.category import Category
+from fab.tools.tool import Tool
+
+
+class NfConfig(Tool):
+    '''This class interfaces with NetCDF's nf-config tool. It is not added
+    to the ToolRepository, it is intended for site-specific configurations
+    to make it easier to query for NetCDF settings.
+    '''
+
+    def __init__(self):
+        super().__init__("nf-config", "nf-config", Category.MISC)
+
+    def get_compiler_flags(self) -> List[str]:
+        """
+        :returns: the compilation flags to use for NetCDF.
+        """
+        flags = self.run(additional_parameters=["--fflags"])
+        return flags.split()
+
+    def get_linker_flags(self) -> List[str]:
+        """
+        :returns: the linker flags to use for NetCDF.
+        """
+        flags = self.run(additional_parameters=["--flibs"])
+        return flags.split()