From 8fee963218430749f37344285828c6860091eb33 Mon Sep 17 00:00:00 2001
From: Lawrence Mitchell <lawrence@wence.uk>
Date: Fri, 26 Jun 2020 17:18:09 +0100
Subject: [PATCH 1/2] codegen: Ensure lower and upper slabs are distinct

When specifying split_iname with both lower and upper slabs, we need
to ensure that for loops shorter than the split length only one of the
two peeled slabs is run. Do so by ensuring that the upper slab is
conditioned on being larger than the end of the lower slab.

Fixes #215.
---
 loopy/codegen/loop.py | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/loopy/codegen/loop.py b/loopy/codegen/loop.py
index b3a877988..bc013307f 100644
--- a/loopy/codegen/loop.py
+++ b/loopy/codegen/loop.py
@@ -80,11 +80,16 @@ def get_slab_decomposition(kernel, iname):
 
         if upper_incr:
             assert upper_incr > 0
-            upper_slab = ("final", isl.BasicSet.universe(space)
-                    .add_constraint(
-                        isl.Constraint.inequality_from_aff(
-                            iname_rel_aff(space,
-                                iname, ">", upper_bound_aff-upper_incr))))
+            upper_bset = isl.BasicSet.universe(space).add_constraint(
+                isl.Constraint.inequality_from_aff(
+                    iname_rel_aff(space,
+                        iname, ">", upper_bound_aff-upper_incr)))
+            if lower_incr:
+                # Ensure that this slab is actually distinct from the
+                # lower one, if it exists.
+                _, lower_bset = lower_slab
+                upper_bset, = upper_bset.subtract(lower_bset).get_basic_sets()
+            upper_slab = ("final", upper_bset)
             upper_bulk_bound = (
                     isl.Constraint.inequality_from_aff(
                         iname_rel_aff(space,
-- 
GitLab


From b527a66a1a155f4338179f0655c3d901b2586d53 Mon Sep 17 00:00:00 2001
From: Lawrence Mitchell <lawrence@wence.uk>
Date: Fri, 26 Jun 2020 18:27:43 +0100
Subject: [PATCH 2/2] test: Check iname slab splitting handles corner cases

See #215.
---
 test/test_split_iname_slabs.py | 66 ++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 test/test_split_iname_slabs.py

diff --git a/test/test_split_iname_slabs.py b/test/test_split_iname_slabs.py
new file mode 100644
index 000000000..47f311ab5
--- /dev/null
+++ b/test/test_split_iname_slabs.py
@@ -0,0 +1,66 @@
+__copyright__ = "Copyright (C) 2020 Lawrence Mitchell"
+
+__license__ = """
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+"""
+import loopy as lp
+import numpy as np
+import pyopencl as cl  # noqa
+import pyopencl.array as clarray
+import pytest
+from loopy.version import LOOPY_USE_LANGUAGE_VERSION_2018_2  # noqa
+from pyopencl.tools import \
+    pytest_generate_tests_for_pyopencl as pytest_generate_tests  # noqa
+
+
+@pytest.fixture
+def vanilla():
+    k = lp.make_kernel("{ [i] : k <= i < n}",
+                       """
+                       a[i] = a[i] + 1
+                       """,
+                       [lp.ValueArg("k", dtype="int32"),
+                        lp.ValueArg("n", dtype="int32"),
+                        lp.GlobalArg("a", shape=(None, ),
+                                        dtype="int32")])
+    k = lp.assume(k, "k >= 0 and n >= k")
+    return k
+
+
+@pytest.fixture
+def split(vanilla):
+    k = lp.split_iname(vanilla, "i", 4, slabs=(1, 1))
+    k = lp.prioritize_loops(k, "i_outer,i_inner")
+    return k
+
+
+@pytest.fixture(params=[(1, 4), (1, 5), (4, 8)],
+                ids=lambda x: "{k=%s, n=%s}" % x)
+def parameters(request):
+    return dict(zip("kn", request.param))
+
+
+def test_split_slabs(ctx_factory, vanilla, split, parameters):
+    ctx = ctx_factory()
+    queue = cl.CommandQueue(ctx)
+    expect = clarray.zeros(queue, 8, dtype=np.int32)
+    actual = clarray.zeros(queue, 8, dtype=np.int32)
+    _, (expect, ) = vanilla(queue, a=expect, **parameters)
+    _, (actual, ) = split(queue, a=actual, **parameters)
+    assert np.array_equal(expect.get(), actual.get())
-- 
GitLab