Ensure (re-)init of RNG at top of INITIALIZE

pyproject.toml

@@ -17,6 +17,7 @@ dependencies = [
     'loguru>=0.7.2',
     'gitpython>=3.1.43',
     'msgspec>=0.19.0',
+    'packaging',
 ]
 description = "ANTLR4 grammars for McStas and McXtrace"
 readme = "README.md"

src/mccode_antlr/reader/registry.py

@@ -519,31 +519,38 @@ def registry_from_specification(spec: str):
 REGISTRY_PRIORITY_HIGHEST=10
 
 
+def _get_remote_repository_version_tags(url):
+    import re
+    import git
+    g = git.cmd.Git()
+    res = g.ls_remote(url, sort='-v:refname', tags=True)
+    ex = re.compile(r'v\d+(?:\.\d+(?:\.\d+)?)?')
+    return list(dict.fromkeys(ex.findall(res)))
+
+def _source_registry_tag():
+    """This causes the confuse config directory to be created, so could fail
+    on read-only systems."""
+    from mccode_antlr.config import config
+    requested_tag = config['mccode_pooch']['tag'].as_str_expanded()
+    registry_url = config['mccode_pooch']['registry'].as_str_expanded()
+    source_url = config['mccode_pooch']['source'].as_str_expanded()
+
+    known_tags = _get_remote_repository_version_tags(registry_url)
+    if requested_tag.lower() == 'latest':
+        requested_tag = known_tags[0]
+    elif requested_tag not in known_tags:
+        raise RuntimeError(f"The specified version tag, {requested_tag}, is not available in {registry_url}")
+    return source_url, registry_url, requested_tag
+
+
+def mccode_registry_version():
+    from packaging.version import Version
+    _, _, tag = _source_registry_tag()
+    return Version(tag)
+
+
 def _mccode_pooch_registries(flavor: Flavor):
-    def get_remote_repository_version_tags(url):
-        import re
-        import git
-        g = git.cmd.Git()
-        res = g.ls_remote(url, sort='-v:refname', tags=True)
-        ex = re.compile(r'v\d+(?:\.\d+(?:\.\d+)?)?')
-        return list(dict.fromkeys(ex.findall(res)))
-
-    def source_registry_tag():
-        """This causes the confuse config directory to be created, so could fail
-        on read-only systems."""
-        from mccode_antlr.config import config
-        requested_tag = config['mccode_pooch']['tag'].as_str_expanded()
-        registry_url = config['mccode_pooch']['registry'].as_str_expanded()
-        source_url = config['mccode_pooch']['source'].as_str_expanded()
-
-        known_tags = get_remote_repository_version_tags(registry_url)
-        if requested_tag.lower() == 'latest':
-            requested_tag = known_tags[0]
-        elif requested_tag not in known_tags:
-            raise RuntimeError(f"The specified version tag, {requested_tag}, is not available in {registry_url}")
-        return source_url, registry_url, requested_tag
-
-    src, reg, tag = source_registry_tag()
+    src, reg, tag = _source_registry_tag()
 
     def make_registry(name):
         return GitHubRegistry(name, src, tag, registry=reg, priority=REGISTRY_PRIORITY_LOWEST)

src/mccode_antlr/translators/c_initialise.py

@@ -225,6 +225,10 @@ def nexus_lines():
 
 
 def cogen_initialize(source, component_declared_parameters, ok_to_skip):
+    from packaging.version import Version
+    from mccode_antlr.reader.registry import mccode_registry_version
+    version = mccode_registry_version()
+
     lines = ["/* *****************************************************************************",
              f"* instrument '{source.name}' and components INITIALISE",
              "***************************************************************************** */",
@@ -244,6 +248,18 @@ def cogen_initialize(source, component_declared_parameters, ok_to_skip):
     lines.extend([
         f'int init(void) {{ /* called by mccode_main for {source.name}:INITIALIZE */',
         '  DEBUG_INSTR();',
+    ])
+    if version > Version("3.5.40"):
+        # McCode https://github.com/mccode-dev/McCode/pull/2227#issuecomment-3613096573
+        # changed `mccode_main.c` and the code-generator to move the random number
+        # seeding before "INITIALIZE" time.
+        # The most-recent release at that time was 3.5.40, so this change is only
+        # compatible with releases after that.
+        lines.extend([
+            '// Initialise rng',
+            '  srandom(_hash(mcseed-1));',
+        ])
+    lines.extend([
         '',
         '  /* code_main/parseoptions/readparams sets instrument parameters value */',
         f'  stracpy(instrument->_name, "{source.name}", {len(source.name)+1});',

src/mccode_antlr/translators/c_raytrace.py

@@ -123,7 +123,7 @@ def cogen_raytrace(source, ok_to_skip):
                 f'      // GROUP {group.name}: from {fn} [{group.first_id}] to {ln} [{1+lid}]',
                 # Skip over when SCATTERED in the group:
                 f'      if (SCATTERED) _particle->_index = {1+lid}; '
-                '// when SCATTERED in GROUP: reach exit of GROUP after {ln}',
+                f'// when SCATTERED in GROUP: reach exit of GROUP after {ln}',
                 #
             ])
             if index == lid: