From 58356197ff0f2ef9d288357b60c8a7387512fed0 Mon Sep 17 00:00:00 2001
From: Andreas Kloeckner <inform@tiker.net>
Date: Sun, 29 Jul 2012 20:40:17 -0400
Subject: [PATCH] Shift responsibility for segmentation to scan_expr.
---
pyopencl/scan.py | 139 ++++++++++++++++++++++++++-------------------
test/test_array.py | 5 +-
2 files changed, 84 insertions(+), 60 deletions(-)
diff --git a/pyopencl/scan.py b/pyopencl/scan.py
index d4744e5c..6565682f 100644
--- a/pyopencl/scan.py
+++ b/pyopencl/scan.py
@@ -47,11 +47,7 @@ from pyopencl.tools import context_dependent_memoize
SHARED_PREAMBLE = CLUDA_PREAMBLE + """//CL//
#define WG_SIZE ${wg_size}
-/* SCAN_EXPR has no right know the indices it is scanning at because
-each index may occur an undetermined number of times in the scan tree,
-and thus index-based side computations cannot be meaningful. */
-
-#define SCAN_EXPR(a, b) ${scan_expr}
+#define SCAN_EXPR(a, b, across_seg_boundary) ${scan_expr}
#define INPUT_EXPR(i) (${input_expr})
%if is_segmented:
#define IS_SEG_START(i, a) (${is_segment_start_expr})
@@ -272,13 +268,15 @@ void ${name_prefix}_scan_intervals(
first_segment_start_in_k_group = unit_base + K*LID_0;
%endif
- if (LID_0 == 0 && unit_base != interval_begin
- %if is_segmented:
- && !l_segment_start_flags[0][0]
- %endif
- )
+ if (LID_0 == 0 && unit_base != interval_begin)
{
- ldata[0][0] = SCAN_EXPR(ldata[K][WG_SIZE - 1], ldata[0][0]);
+ ldata[0][0] = SCAN_EXPR(ldata[K][WG_SIZE - 1], ldata[0][0],
+ %if is_segmented:
+ (l_segment_start_flags[0][0])
+ %else:
+ false
+ %endif
+ );
}
// }}}
@@ -308,11 +306,16 @@ void ${name_prefix}_scan_intervals(
first_segment_start_in_k_group = min(
first_segment_start_in_k_group,
seq_i);
- sum = tmp;
}
- else
%endif
- sum = SCAN_EXPR(sum, tmp);
+
+ sum = SCAN_EXPR(sum, tmp,
+ %if is_segmented:
+ (l_segment_start_flags[k][LID_0])
+ %else:
+ false
+ %endif
+ );
ldata[k][LID_0] = sum;
}
@@ -357,12 +360,13 @@ void ${name_prefix}_scan_intervals(
if (K*LID_0 < offset_end)
% endif
{
- %if is_segmented:
- if (l_first_segment_start_in_subtree[LID_0] == NO_SEG_BOUNDARY)
- val = SCAN_EXPR(tmp, val);
- %else:
- val = SCAN_EXPR(tmp, val);
- %endif
+ val = SCAN_EXPR(tmp, val,
+ %if is_segmented:
+ (l_first_segment_start_in_subtree[LID_0] != NO_SEG_BOUNDARY)
+ %else:
+ false
+ %endif
+ );
}
%if is_segmented:
@@ -428,19 +432,19 @@ void ${name_prefix}_scan_intervals(
for(index_type k = 0; k < K; k++)
{
- bool do_update = true;
%if is_tail:
- do_update = K * LID_0 + k < offset_end;
+ if (K * LID_0 + k < offset_end)
%endif
- %if is_segmented:
- do_update = unit_base + K * LID_0 + k
- < first_segment_start_in_k_group;
- %endif
-
- if (do_update)
{
scan_type tmp = ldata[k][LID_0];
- ldata[k][LID_0] = SCAN_EXPR(sum, tmp);
+ ldata[k][LID_0] = SCAN_EXPR(sum, tmp,
+ %if is_segmented:
+ (unit_base + K * LID_0 + k
+ >= first_segment_start_in_k_group)
+ %else:
+ false
+ %endif
+ );
}
}
}
@@ -542,28 +546,24 @@ void ${name_prefix}_final_update(
index_type update_i = interval_begin+LID_0;
- <%def name="update_loop_plain(end)">
- for(; update_i < ${end}; update_i += WG_SIZE)
- {
- scan_type partial_val = partial_scan_buffer[update_i];
- scan_type item = SCAN_EXPR(carry, partial_val);
- index_type i = update_i;
-
- { ${output_statement}; }
- }
- </%def>
-
- // {{{ update to the first intra-interval segment boundary
-
%if is_segmented:
index_type seg_end = min(first_seg_start_in_interval, interval_end);
- ${update_loop_plain("seg_end")}
- carry = ${neutral};
%endif
- // }}}
+ for(; update_i < interval_end; update_i += WG_SIZE)
+ {
+ scan_type partial_val = partial_scan_buffer[update_i];
+ scan_type item = SCAN_EXPR(carry, partial_val,
+ %if is_segmented:
+ (update_i >= seg_end)
+ %else:
+ false
+ %endif
+ );
+ index_type i = update_i;
- ${update_loop_plain("interval_end")}
+ { ${output_statement}; }
+ }
// }}}
%else:
@@ -585,10 +585,13 @@ void ${name_prefix}_final_update(
{
scan_type tmp = partial_scan_buffer[update_i];
- %if is_segmented:
- if (update_i < first_seg_start_in_interval)
- %endif
- { tmp = SCAN_EXPR(carry, tmp); }
+ tmp = SCAN_EXPR(carry, tmp,
+ %if is_segmented:
+ (update_i >= first_seg_start_in_interval)
+ %else:
+ false
+ %endif
+ );
ldata[LID_0] = tmp;
@@ -703,7 +706,7 @@ _PREFIX_WORDS = set("""
_IGNORED_WORDS = set("""
typedef for endfor if void while endwhile endfor endif else const printf
- None return bool n char
+ None return bool n char true false
set iteritems len setdefault
@@ -716,7 +719,7 @@ _IGNORED_WORDS = set("""
_final_update _scan_intervals _debug_scan
- positions all padded integer its previous write based true writes 0
+ positions all padded integer its previous write based writes 0
has local worth scan_expr to read cannot not X items False bank
four beginning follows applicable item min each indices works side
scanning right summed relative used id out index avoid current state
@@ -747,7 +750,7 @@ _IGNORED_WORDS = set("""
update_loop first_seg
a b prev_item i prev_item_unavailable_with_local_update prev_value
- N NO_SEG_BOUNDARY
+ N NO_SEG_BOUNDARY across_seg_boundary
""".split())
def _make_template(s):
@@ -807,6 +810,21 @@ class _GenericScanKernelBase(object):
modified by the scan, it should live in `b`.
This expression may call functions given in the *preamble*.
+
+ Another value available to this expression is `across_seg_boundary`,
+ a C `bool` indicating whether this scan update is crossing a
+ segment boundary, as defined by `is_segment_start_expr`.
+ The scan routine does not implement segmentation
+ semantics on its own. It relies on `scan_expr` to do this.
+ This value is available (but always `false`) even for a
+ non-segmented scan.
+
+ .. note::
+
+ In early pre-releases of the segmented scan,
+ segmentation semantics were implemented *without*
+ relying on `scan_expr`.
+
:arg input_expr: A C expression, encoded as a string, resulting
in the values to which the scan is applied. This may be used
to apply a mapping to values stored in *arguments* before being
@@ -1230,13 +1248,16 @@ void ${name_prefix}_debug_scan(
prev_item = item;
%if is_segmented:
- {
- bool is_seg_start = IS_SEG_START(i, my_val);
- if (is_seg_start)
- prev_item = ${neutral};
- }
+ bool is_seg_start = IS_SEG_START(i, my_val);
%endif
- item = SCAN_EXPR(prev_item, my_val);
+
+ item = SCAN_EXPR(prev_item, my_val,
+ %if is_segmented:
+ is_seg_start
+ %else:
+ false
+ %endif
+ );
{
${output_statement};
diff --git a/test/test_array.py b/test/test_array.py
index bef04fb9..694f5a51 100644
--- a/test/test_array.py
+++ b/test/test_array.py
@@ -957,7 +957,7 @@ def test_segmented_scan(ctx_factory):
arguments="__global %s *ary, __global char *segflags, __global %s *out"
% (ctype, ctype),
input_expr="ary[i]",
- scan_expr="a+b", neutral="0",
+ scan_expr="across_seg_boundary ? b : (a+b)", neutral="0",
is_segment_start_expr="segflags[i]",
output_statement=output_statement,
options=[])
@@ -1117,6 +1117,9 @@ def test_view(ctx_factory):
@pytools.test.mark_test.opencl
def no_test_slice(ctx_factory):
+ context = ctx_factory()
+ queue = cl.CommandQueue(context)
+
from pyopencl.clrandom import rand as clrand
l = 20000
--
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