From b981be01012859e3d61e134932d8dd6cdfedc9a2 Mon Sep 17 00:00:00 2001
From: mloubout <mathias.louboutin@gmail.com>
Date: Sat, 18 Jan 2025 18:16:03 -0500
Subject: [PATCH] compiler: fix missing algorithm include for min/max

---
 devito/operator/operator.py        |  5 +++--
 devito/passes/iet/languages/CXX.py |  1 +
 devito/passes/iet/misc.py          | 31 ++++++++++++++++--------------
 tests/test_gpu_openacc.py          | 13 ++++++++++++-
 4 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/devito/operator/operator.py b/devito/operator/operator.py
index 3966da4378..a5fef9b84f 100644
--- a/devito/operator/operator.py
+++ b/devito/operator/operator.py
@@ -470,6 +470,7 @@ def _lower_iet(cls, uiet, profiler=None, **kwargs):
             * Finalize (e.g., symbol definitions, array casts)
         """
         name = kwargs.get("name", "Kernel")
+        lang = cls._Target.lang()
 
         # Wrap the IET with an EntryFunction (a special Callable representing
         # the entry point of the generated library)
@@ -488,10 +489,10 @@ def _lower_iet(cls, uiet, profiler=None, **kwargs):
         cls._Target.instrument(graph, profiler=profiler, **kwargs)
 
         # Extract the necessary macros from the symbolic objects
-        generate_macros(graph, **kwargs)
+        generate_macros(graph, lang=lang, **kwargs)
 
         # Add type specific metadata
-        lower_dtypes(graph, lang=cls._Target.lang(), **kwargs)
+        lower_dtypes(graph, lang=lang, **kwargs)
 
         # Target-independent optimizations
         minimize_symbols(graph)
diff --git a/devito/passes/iet/languages/CXX.py b/devito/passes/iet/languages/CXX.py
index 17003c0d8f..bfa6bebe35 100644
--- a/devito/passes/iet/languages/CXX.py
+++ b/devito/passes/iet/languages/CXX.py
@@ -45,6 +45,7 @@ class CXXBB(LangBB):
 
     mapper = {
         'header-memcpy': 'string.h',
+        'header-algorithm': 'algorithm',
         'host-alloc': lambda i, j, k:
             Call('posix_memalign', (i, j, k)),
         'host-alloc-pin': lambda i, j, k:
diff --git a/devito/passes/iet/misc.py b/devito/passes/iet/misc.py
index 28e1cc4f7b..d978936053 100644
--- a/devito/passes/iet/misc.py
+++ b/devito/passes/iet/misc.py
@@ -144,7 +144,7 @@ def generate_macros(graph, **kwargs):
 
 
 @iet_pass
-def _generate_macros(iet, tracker=None, **kwargs):
+def _generate_macros(iet, tracker=None, lang=None, **kwargs):
     # Derive the Macros necessary for the FIndexeds
     iet = _generate_macros_findexeds(iet, tracker=tracker, **kwargs)
 
@@ -152,7 +152,8 @@ def _generate_macros(iet, tracker=None, **kwargs):
     headers = sorted((ccode(define), ccode(expr)) for define, expr in headers)
 
     # Generate Macros from higher-level SymPy objects
-    headers.extend(_generate_macros_math(iet))
+    mheaders, includes = _generate_macros_math(iet, lang=lang)
+    headers.extend(mheaders)
 
     # Remove redundancies while preserving the order
     headers = filter_ordered(headers)
@@ -160,7 +161,6 @@ def _generate_macros(iet, tracker=None, **kwargs):
     # Some special Symbols may represent Macros defined in standard libraries,
     # so we need to include the respective includes
     limits = FindApplications(ValueLimit).visit(iet)
-    includes = set()
     if limits & (set(limits_mapper[np.int32]) | set(limits_mapper[np.int64])):
         includes.add('limits.h')
     elif limits & (set(limits_mapper[np.float32]) | set(limits_mapper[np.float64])):
@@ -195,35 +195,38 @@ def _generate_macros_findexeds(iet, sregistry=None, tracker=None, **kwargs):
     return iet
 
 
-def _generate_macros_math(iet):
+def _generate_macros_math(iet, lang=None):
     headers = []
+    includes = []
     for i in FindApplications().visit(iet):
-        headers.extend(_lower_macro_math(i))
+        header, include = _lower_macro_math(i, lang)
+        headers.extend(header)
+        includes.extend(include)
 
-    return headers
+    return headers, set(includes) - {None}
 
 
 @singledispatch
-def _lower_macro_math(expr):
-    return ()
+def _lower_macro_math(expr, lang):
+    return (), {}
 
 
 @_lower_macro_math.register(Min)
 @_lower_macro_math.register(sympy.Min)
-def _(expr):
+def _(expr, lang):
     if has_integer_args(*expr.args) and len(expr.args) == 2:
-        return (('MIN(a,b)', ('(((a) < (b)) ? (a) : (b))')),)
+        return (('MIN(a,b)', ('(((a) < (b)) ? (a) : (b))')),), {}
     else:
-        return ()
+        return (), (lang.get('header-algorithm'),)
 
 
 @_lower_macro_math.register(Max)
 @_lower_macro_math.register(sympy.Max)
-def _(expr):
+def _(expr, lang):
     if has_integer_args(*expr.args) and len(expr.args) == 2:
-        return (('MAX(a,b)', ('(((a) > (b)) ? (a) : (b))')),)
+        return (('MAX(a,b)', ('(((a) > (b)) ? (a) : (b))')),), {}
     else:
-        return ()
+        return (), (lang.get('header-algorithm'),)
 
 
 @_lower_macro_math.register(SafeInv)
diff --git a/tests/test_gpu_openacc.py b/tests/test_gpu_openacc.py
index bdf732a12d..8c4813db0b 100644
--- a/tests/test_gpu_openacc.py
+++ b/tests/test_gpu_openacc.py
@@ -2,7 +2,7 @@
 import numpy as np
 
 from devito import (Grid, Function, TimeFunction, SparseTimeFunction, Eq, Operator,
-                    norm, solve)
+                    norm, solve, Max)
 from conftest import skipif, assert_blocking, opts_device_tiling
 from devito.data import LEFT
 from devito.exceptions import InvalidOperator
@@ -171,6 +171,17 @@ def test_multi_tile_blocking_structure(self):
             assert len(iters) == len(v)
             assert all(i.step == j for i, j in zip(iters, v))
 
+    def test_std_max(self):
+        grid = Grid(shape=(3, 3, 3))
+        x, y, z = grid.dimensions
+
+        u = Function(name='u', grid=grid)
+
+        op = Operator(Eq(u, Max(1.2 * x / y, 2.3 * y / x)),
+                      platform='nvidiaX', language='openacc')
+
+        assert '<algorithm>' in str(op)
+
 
 class TestOperator: