(Closes #3157, #3306) Initial implementation of maximal parallel region trans.

changelog

@@ -1,3 +1,7 @@
+   51) PR #3205 for #3306 and towards #3157. Initial implementation of
+   a generic MaximalRegionTrans and specialisations to create spanning
+   OMPParallel regions and NEMO Profiling regions.
+
    50) PR #3338 for #1651. Fixes Reference2ArrayRange issues with
    capitalisation and test nested WHEREs.
 

examples/nemo/eg7/openmp_cpu_nowait_trans.py

@@ -42,67 +42,21 @@
         OMPLoopTrans,
         OMPMinimiseSyncTrans,
         TransformationError,
-        OMPParallelTrans
+        MaximalOMPParallelRegionTrans
 )
 from psyclone.psyir.nodes import (
         Assignment,
         Directive,
-        IfBlock,
         Loop,
-        OMPBarrierDirective,
-        OMPDoDirective,
         Routine,
 )
 
 
-def add_parallel_region_to_contiguous_directives(schedule):
-    '''Adds OMPParallelDirective nodes around areas of the schedule with
-    contiguous OpenMP directives.
-
-    :param schedule: The Schedule to add OpenMPParallelDirectives to.
-    :type schedule: :py:class:`psyclone.nodes.Schedule`
-    '''
-    par_trans = OMPParallelTrans()
-    start = -1
-    end = -1
-    sets = []
-    # Loop through the children, if its an OpenMP directive add it
-    # to the current set
-    for child in schedule:
-        if isinstance(child, (OMPDoDirective, OMPBarrierDirective)):
-            if start < 0:
-                start = child.position
-            end = child.position + 1
-        else:
-            # If we have a non OMPDodirective/OMPBarrierDirective then add
-            # an OMPParallelDirective if needed.
-            if start >= 0:
-                sets.append((start, end))
-                start = -1
-                end = -1
-            # Recurse appropriately to sub schedules:
-            if isinstance(child, Loop):
-                add_parallel_region_to_contiguous_directives(child.loop_body)
-            elif isinstance(child, IfBlock):
-                add_parallel_region_to_contiguous_directives(child.if_body)
-                if child.else_body:
-                    add_parallel_region_to_contiguous_directives(
-                        child.else_body
-                    )
-    # If we get to the end and need to enclose some nodes in a parallel
-    # directive we do it now
-    if start >= 0:
-        sets.append((start, end))
-
-    for subset in sets[::-1]:
-        par_trans.apply(schedule[subset[0]:subset[1]])
-
-
 def trans(psyir):
     ''' Adds OpenMP Loop directives with nowait to Nemo loops over levels.
-    This is followed by applying OpenMP parallel directives as required,
-    before removing barriers where possible.
-
+    This is followed by applying OpenMP parallel directives as required
+    with the OMPMaximalParallelRegionTrans, before removing barriers where
+    possible.
 
     :param psyir: the PSyIR of the provided file.
     :type psyir: :py:class:`psyclone.psyir.nodes.FileContainer`
@@ -130,5 +84,5 @@ def trans(psyir):
     # Apply the largest possible parallel regions and remove any barriers that
     # can be removed.
     for routine in psyir.walk(Routine):
-        add_parallel_region_to_contiguous_directives(routine)
+        MaximalOMPParallelRegionTrans().apply(routine)
         minsync_trans.apply(routine)

examples/nemo/scripts/utils.py

@@ -40,14 +40,14 @@
 
 from psyclone.domain.common.transformations import KernelModuleInlineTrans
 from psyclone.psyir.nodes import (
-    Assignment, Loop, Directive, Node, Reference, CodeBlock, Call, Return,
-    IfBlock, Routine, Schedule, IntrinsicCall, StructureReference)
+    Assignment, Loop, Directive, Node, Reference, CodeBlock, Call,
+    Routine, Schedule, IntrinsicCall, StructureReference, IfBlock)
 from psyclone.psyir.symbols import DataSymbol
 from psyclone.psyir.transformations import (
     ArrayAssignment2LoopsTrans, HoistLoopBoundExprTrans, HoistLocalArraysTrans,
     HoistTrans, InlineTrans, Maxval2LoopTrans, ProfileTrans,
     OMPMinimiseSyncTrans, Reference2ArrayRangeTrans,
-    ScalarisationTrans, IncreaseRankLoopArraysTrans)
+    ScalarisationTrans, IncreaseRankLoopArraysTrans, MaximalRegionTrans)
 from psyclone.transformations import TransformationError
 
 # USE statements to chase to gather additional symbol information.
@@ -474,6 +474,40 @@ def add_profiling(children: Union[List[Node], Schedule]):
         attempt to add profiling regions.
 
     '''
+    class MaximalProfilingOutsideDirectivesTrans(MaximalRegionTrans):
+        '''Applies Profiling to the largest possible region outside of
+        directive regions.
+
+        :param routine_name: The name of the Routine being profiled.
+        '''
+        # We purposely don't encompase Directive, or Return statements
+        # (which would create unclosed hooks).
+        _allowed_contiguous_statements = (Assignment, Call, CodeBlock)
+        _transformation = ProfileTrans
+
+        def _satisfies_minimum_region_rules(self, region: list[Node]) -> bool:
+            '''Returns whether the provided node list satisfies the
+            requirements to create a region for the ProfileTrans.
+
+            :param region: The candidate region to have the transformation
+                applied.
+            :returns: whether the provided node list should have profiling
+                applied.
+            '''
+            if len(region) == 1:
+                if (isinstance(region[0], CodeBlock) and
+                        len(region[0].get_ast_nodes) == 1):
+                    # Don't create profiling regions for CodeBlocks consisting
+                    # of a single statement.
+                    return False
+                if (isinstance(region[0], IfBlock) and
+                    "was_single_stmt" in region[0].annotations and
+                        isinstance(region[0].if_body[0], CodeBlock)):
+                    # We also don't put single statements consisting of
+                    # 'If(condition) call blah()' inside profiling regions.
+                    return False
+            return super()._satisfies_minimum_region_rules(region)
+
     if children and isinstance(children, Schedule):
         # If we are given a Schedule, we look at its children.
         children = children.children
@@ -486,56 +520,6 @@ def add_profiling(children: Union[List[Node], Schedule]):
     parent_routine = children[0].ancestor(Routine)
     if parent_routine and parent_routine.return_symbol:
         return
-
-    node_list = []
-    for child in children[:]:
-        # Do we want this node to be included in a profiling region?
-        if child.walk((Directive, Return)):
-            # It contains a directive or return statement so we put what we
-            # have so far inside a profiling region.
-            add_profile_region(node_list)
-            # A node that is not included in a profiling region marks the
-            # end of the current candidate region so reset the list.
-            node_list = []
-            # Now we go down a level and try again without attempting to put
-            # profiling below directives or within Assignments
-            if isinstance(child, IfBlock):
-                add_profiling(child.if_body)
-                add_profiling(child.else_body)
-            elif not isinstance(child, (Assignment, Directive)):
-                add_profiling(child.children)
-        else:
-            # We can add this node to our list for the current region
-            node_list.append(child)
-    add_profile_region(node_list)
-
-
-def add_profile_region(nodes):
-    '''
-    Attempt to put the supplied list of nodes within a profiling region.
-
-    :param nodes: list of sibling PSyIR nodes to enclose.
-    :type nodes: list of :py:class:`psyclone.psyir.nodes.Node`
-
-    '''
-    if nodes:
-        # Check whether we should be adding profiling inside this routine
-        routine_name = nodes[0].ancestor(Routine).name.lower()
-        if any(ignore in routine_name for ignore in PROFILING_IGNORE):
-            return
-        if len(nodes) == 1:
-            if isinstance(nodes[0], CodeBlock) and \
-               len(nodes[0].get_ast_nodes) == 1:
-                # Don't create profiling regions for CodeBlocks consisting
-                # of a single statement
-                return
-            if isinstance(nodes[0], IfBlock) and \
-               "was_single_stmt" in nodes[0].annotations and \
-               isinstance(nodes[0].if_body[0], CodeBlock):
-                # We also don't put single statements consisting of
-                # 'IF(condition) CALL blah()' inside profiling regions
-                return
-        try:
-            ProfileTrans().apply(nodes)
-        except TransformationError:
-            pass
+    routine_name = parent_routine.name if parent_routine else ""
+    if routine_name not in PROFILING_IGNORE:
+        MaximalProfilingOutsideDirectivesTrans().apply(children)

src/psyclone/psyir/transformations/__init__.py

@@ -94,6 +94,8 @@
 from psyclone.psyir.transformations.loop_trans import LoopTrans
 from psyclone.psyir.transformations.value_range_check_trans import (
     ValueRangeCheckTrans)
+from psyclone.psyir.transformations.maximal_region_trans import (
+    MaximalRegionTrans)
 from psyclone.psyir.transformations.omp_critical_trans import (
     OMPCriticalTrans)
 from psyclone.psyir.transformations.omp_loop_trans import OMPLoopTrans
@@ -126,6 +128,9 @@
     OMPTaskloopTrans
 from psyclone.psyir.transformations.omp_declare_target_trans import \
     OMPDeclareTargetTrans
+from psyclone.psyir.transformations.maximal_omp_parallel_region_trans import (
+    MaximalOMPParallelRegionTrans
+)
 from psyclone.psyir.transformations.omp_parallel_trans import (
     OMPParallelTrans,
 )
@@ -182,6 +187,8 @@
     "ParallelRegionTrans",
     "OMPTaskloopTrans",
     "OMPDeclareTargetTrans",
+    "MaximalRegionTrans",
     "OMPCriticalTrans",
+    "MaximalOMPParallelRegionTrans",
     "OMPParallelTrans",
 ]

src/psyclone/psyir/transformations/maximal_omp_parallel_region_trans.py

@@ -0,0 +1,93 @@
+# -----------------------------------------------------------------------------
+# BSD 3-Clause License
+#
+# Copyright (c) 2017-2025, Science and Technology Facilities Council.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+#   list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+#
+# * Neither the name of the copyright holder nor the names of its
+#   contributors may be used to endorse or promote products derived from
+#   this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+# -----------------------------------------------------------------------------
+# Authors A. B. G. Chalk, STFC Daresbury Lab
+
+'''This module contains the MaximalOMPParallelRegionTrans.'''
+
+from typing import Union
+
+from psyclone.psyir.nodes import (
+        OMPTaskwaitDirective,
+        OMPBarrierDirective,
+        OMPSerialDirective,
+        OMPTaskloopDirective,
+        OMPDoDirective,
+        OMPLoopDirective,
+        OMPTaskDirective,
+        DynamicOMPTaskDirective,
+        Node,
+        Schedule
+)
+from psyclone.psyir.transformations.maximal_region_trans import (
+        MaximalRegionTrans)
+from psyclone.psyir.transformations.omp_parallel_trans import OMPParallelTrans
+from psyclone.utils import transformation_documentation_wrapper
+
+
+@transformation_documentation_wrapper
+class MaximalOMPParallelRegionTrans(MaximalRegionTrans):
+    '''Applies OpenMP Parallel directives around the largest possible sections
+    of the input.
+
+    At current, this will never place OpenMP parallel sections around
+    Assignments that are outside of another OpenMP directive. See #3157 and
+    the discussion on #3205 for more detail.'''
+    # The type of parallel transformation to be applied to the input region.
+    _transformation = OMPParallelTrans
+    # Tuple of statement nodes allowed inside the _transformation
+    _allowed_contiguous_statements = (
+        OMPTaskwaitDirective,
+        OMPBarrierDirective,
+        OMPSerialDirective,
+        OMPTaskloopDirective,
+        OMPDoDirective,
+        OMPLoopDirective,
+        OMPTaskDirective,
+        DynamicOMPTaskDirective,
+    )
+    _required_nodes = (
+        OMPSerialDirective,
+        OMPTaskloopDirective,
+        OMPDoDirective,
+        OMPLoopDirective,
+        OMPTaskDirective,
+        DynamicOMPTaskDirective,
+    )
+
+    def apply(self, nodes: Union[Node, Schedule, list[Node]], **kwargs):
+        '''Applies the transformation to the nodes provided.
+
+        :param nodes: can be a single node, a schedule or a list of nodes.
+        '''
+        super().apply(nodes, **kwargs)