[PATCH weston v2 12/21] Introduce a 'double fixed' data type abstraction
Jonas Ådahl
jadahl at gmail.com
Wed May 13 03:26:33 PDT 2015
The 'double fixed' value type is a fixed point data type implemented as
two signed 32 bit integers. It is intended to be sent over the wire and
used when wl_fixed_t is not detailed enough.
Two helper functions are introduced: wl_double_fixed_to_double and
wl_double_fixed_from_double that can be used for conversion.
The type is implemented by separating the integral part from the
fractional part, storing them in individual signed 32 bit integers.
Converting to a double could be implemented with:
double = integral + fraction / 2147483648
Converting to a double could be implemented with:
integral = integral part of double
fraction = fractional part of double * 2147483648
The implementation provided in this patch is slightly faster than the
above methods, but assumes that the IEEE 754 double-precision binary
floating-point format is used internally. It is based on the wl_fixed_t
conversion functions from wayland-util.h.
Signed-off-by: Jonas Ådahl <jadahl at gmail.com>
---
Makefile.am | 6 +++
shared/util.h | 57 +++++++++++++++++++++
tests/double-fixed-benchmark.c | 110 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 173 insertions(+)
create mode 100644 shared/util.h
create mode 100644 tests/double-fixed-benchmark.c
diff --git a/Makefile.am b/Makefile.am
index 2f16fac..0a30cb4 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -990,6 +990,7 @@ noinst_PROGRAMS += \
$(shared_tests) \
$(weston_tests) \
$(ivi_tests) \
+ double-fixed-benchmark \
matrix-test
test_module_ldflags = \
@@ -1102,6 +1103,11 @@ matrix_test_SOURCES = \
matrix_test_CPPFLAGS = -DUNIT_TEST
matrix_test_LDADD = -lm -lrt
+double_fixed_benchmark_SOURCES = \
+ tests/double-fixed-benchmark.c \
+ shared/util.h
+double_fixed_benchmark_LDADD = -lm
+
if ENABLE_IVI_SHELL
module_tests += \
ivi-layout-internal-test.la \
diff --git a/shared/util.h b/shared/util.h
new file mode 100644
index 0000000..97a6f9b
--- /dev/null
+++ b/shared/util.h
@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2008 Kristian Høgsberg
+ * Copyright © 2015 Red Hat Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission. The copyright holders make no representations
+ * about the suitability of this software for any purpose. It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#ifndef WESTON_SHARED_UTIL_H
+#define WESTON_SHARED_UTIL_H
+
+#include <math.h>
+
+static inline double
+wl_double_fixed_to_double(int32_t i, int32_t f)
+{
+ union {
+ double d;
+ int64_t i;
+ } u;
+
+ u.i = ((1023LL + (52LL - 31LL)) << 52) + (1LL << 51) + f;
+
+ return i + (u.d - (3LL << (52 - 32)));
+}
+
+static inline void
+wl_double_fixed_from_double(double d, int32_t *i, int32_t *f)
+{
+ double integral;
+ union {
+ double d;
+ int64_t i;
+ } u;
+
+ u.d = modf(d, &integral) + (3LL << (51 - 31));
+
+ *i = integral;
+ *f = u.i;
+}
+
+#endif /* WESTON_SHARED_UTIL_H */
diff --git a/tests/double-fixed-benchmark.c b/tests/double-fixed-benchmark.c
new file mode 100644
index 0000000..e4e5685
--- /dev/null
+++ b/tests/double-fixed-benchmark.c
@@ -0,0 +1,110 @@
+/*
+ * Copyright © 2012 Intel Corporation
+ * Copyright © 2015 Red Hat Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission. The copyright holders make no representations
+ * about the suitability of this software for any purpose. It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <time.h>
+#include <assert.h>
+#include <stdint.h>
+#include "shared/util.h"
+
+volatile double global_d;
+
+static void
+noop_conversion(void)
+{
+ int32_t fp;
+
+ union {
+ int64_t i;
+ double d;
+ } u;
+
+ for (fp = 0; fp < INT32_MAX; fp++) {
+ u.i = fp;
+ global_d = u.d;
+ }
+}
+
+static void
+magic_conversion(void)
+{
+ int32_t fp;
+
+ for (fp = 0; fp < INT32_MAX; fp++) {
+ global_d = wl_double_fixed_to_double(fp, fp);
+ }
+}
+
+static void
+mul_conversion(void)
+{
+ int32_t fp;
+
+ for (fp = 0; fp < INT32_MAX; fp++) {
+ global_d = fp + fp / 2147483648.0;
+ }
+}
+
+double factor = 2147483648.0;
+
+static void
+div_conversion(void)
+{
+ int32_t fp;
+
+ for (fp = 0; fp < INT32_MAX; fp++) {
+ global_d = fp + fp / factor;
+ }
+}
+
+static void
+benchmark(const char *s, void (*f)(void))
+{
+ struct timespec start, stop, elapsed;
+
+ clock_gettime(CLOCK_MONOTONIC, &start);
+ f();
+ clock_gettime(CLOCK_MONOTONIC, &stop);
+
+ elapsed.tv_sec = stop.tv_sec - start.tv_sec;
+ elapsed.tv_nsec = stop.tv_nsec - start.tv_nsec;
+ if (elapsed.tv_nsec < 0) {
+ elapsed.tv_nsec += 1000000000;
+ elapsed.tv_sec--;
+ }
+ printf("benchmarked %s:\t%ld.%09lds\n",
+ s, elapsed.tv_sec, elapsed.tv_nsec);
+}
+
+int
+main(int argc, char *argv[])
+{
+ benchmark("noop", noop_conversion);
+ benchmark("magic", magic_conversion);
+ benchmark("div", div_conversion);
+ benchmark("mul", mul_conversion);
+
+ return 0;
+}
--
2.1.4
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