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PEP 418: Add precision in Python of FreeBSD clocks

This commit is contained in:
Victor Stinner 2012-04-13 23:24:44 +02:00
parent 5837b185c5
commit 165038702e
2 changed files with 22 additions and 19 deletions
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33
pep-0418.txt
View File

@ -678,8 +678,8 @@ NTP has different methods to adjust a clock:
* "slewing": change the clock frequency to be slightly faster or * "slewing": change the clock frequency to be slightly faster or
slower (which is done with ``adjtime()``). Since the slew rate is slower (which is done with ``adjtime()``). Since the slew rate is
limited to 0.5 ms/s, each second of adjustment requires an limited to 0.5 millisecond per second, each second of adjustment requires an
amortization interval of 2000 s. Thus, an adjustment of many amortization interval of 2000 seconds. Thus, an adjustment of many
seconds can take hours or days to amortize. seconds can take hours or days to amortize.
* "stepping": jump by a large amount in a single discrete step (which * "stepping": jump by a large amount in a single discrete step (which
is done with ``settimeofday()``) is done with ``settimeofday()``)
@ -713,6 +713,7 @@ CLOCK_HIGHRES 1 ns No Yes ?
CLOCK_MONOTONIC 1 ns Slewed on Linux Yes No CLOCK_MONOTONIC 1 ns Slewed on Linux Yes No
CLOCK_MONOTONIC_RAW 1 ns No Yes No CLOCK_MONOTONIC_RAW 1 ns No Yes No
CLOCK_BOOTTIME 1 ns ? Yes Yes CLOCK_BOOTTIME 1 ns ? Yes Yes
CLOCK_UPTIME 1 ns No Yes ?
mach_absolute_time() 1 ns No Yes No mach_absolute_time() 1 ns No Yes No
QueryPerformanceCounter() \- No Yes ? QueryPerformanceCounter() \- No Yes ?
GetTickCount[64]() 1 ms No Yes Yes GetTickCount[64]() 1 ms No Yes Yes
@ -724,14 +725,15 @@ Examples of clock precision on x86_64:
========================= ================ ========= =================== ========================= ================ ========= ===================
Name Operating system Precision Precision in Python Name Operating system Precision Precision in Python
========================= ================ ========= =================== ========================= ================ ========= ===================
CLOCK_MONOTONIC_RAW Linux 3.2 1 ns 3.0 µs CLOCK_MONOTONIC_RAW Linux 3.2 1 ns 3 µs
CLOCK_MONOTONIC Linux 3.2 1 ns 1.6 µs CLOCK_MONOTONIC Linux 3.2 1 ns 2 µs
CLOCK_HIGHRES SunOS 5.11 2 ns ? CLOCK_HIGHRES SunOS 5.11 2 ns ?
CLOCK_MONOTONIC SunOS 5.11 2 ns ? CLOCK_MONOTONIC SunOS 5.11 2 ns ?
QueryPerformanceCounter Windows Seven 10 ns ? QueryPerformanceCounter Windows Seven 10 ns ?
CLOCK_MONOTONIC FreeBSD 8.2 11 ns ? CLOCK_UPTIME FreeBSD 8.2 11 ns 9 µs
CLOCK_MONOTONIC FreeBSD 8.2 11 ns 7 µs
CLOCK_MONOTONIC OpenBSD 5.0 10 ms ? CLOCK_MONOTONIC OpenBSD 5.0 10 ms ?
GetTickCount Windows Seven 15.6 ms ? GetTickCount Windows Seven 16 ms ?
========================= ================ ========= =================== ========================= ================ ========= ===================
For CLOCK_xxx clocks, the precision of this table is the result of For CLOCK_xxx clocks, the precision of this table is the result of
@ -974,11 +976,11 @@ Examples of clock precision on x86_64:
========================= ================ ========= =================== ========================= ================ ========= ===================
Name Operating system Precision Precision in Python Name Operating system Precision Precision in Python
========================= ================ ========= =================== ========================= ================ ========= ===================
CLOCK_REALTIME Linux 3.2 1 ns 1.9 µs CLOCK_REALTIME Linux 3.2 1 ns 2 µs
CLOCK_REALTIME FreeBSD 8.2 11 ns ? CLOCK_REALTIME FreeBSD 8.2 11 ns 7 µs
CLOCK_REALTIME SunOS 5.11 10 ms ? CLOCK_REALTIME SunOS 5.11 10 ms ?
CLOCK_REALTIME OpenBSD 5.0 10 ms ? CLOCK_REALTIME OpenBSD 5.0 10 ms ?
GetSystemTimeAsFileTime Windows Seven 15.6 ms ? GetSystemTimeAsFileTime Windows Seven 16 ms ?
========================= ================ ========= =================== ========================= ================ ========= ===================
For CLOCK_REALTIME, the precision of this table is the result of For CLOCK_REALTIME, the precision of this table is the result of
@ -1042,14 +1044,15 @@ Examples of clock precision on x86_64:
========================= ================ ========= =================== ========================= ================ ========= ===================
Name Operating system Precision Precision in Python Name Operating system Precision Precision in Python
========================= ================ ========= =================== ========================= ================ ========= ===================
CLOCK_PROCESS_CPUTIME_ID Linux 3.2 1 ns 3.3 µs CLOCK_PROCESS_CPUTIME_ID Linux 3.2 1 ns 3 µs
clock() SunOS 5.11 1 µs ? clock() SunOS 5.11 1 µs ?
getrusage() Linux 3.0 4 ms 4 ms getrusage() Linux 3.0 4 ms 4 ms
clock() FreeBSD 8.2 7.8 ms ? getrusage() FreeBSD 8.2 - 1 µs
clock() FreeBSD 8.2 8 ms 8 ms
clock() Linux 3.2 1 µs 10 ms clock() Linux 3.2 1 µs 10 ms
times() Linux 3.0 10 ms 10 ms times() Linux 3.0 10 ms 10 ms
clock() OpenBSD 5.0 10 ms ? clock() OpenBSD 5.0 10 ms ?
GetProcessTimes() Windows Seven 15.6 ms ? GetProcessTimes() Windows Seven 16 ms ?
========================= ================ ========= =================== ========================= ================ ========= ===================
The precision of clock() in this table is the result of 1 / The precision of clock() in this table is the result of 1 /
@ -1102,9 +1105,9 @@ Examples of clock precision on x86_64:
========================= ================ =============== =================== ========================= ================ =============== ===================
Name Operating system Precision Precision in Python Name Operating system Precision Precision in Python
========================= ================ =============== =================== ========================= ================ =============== ===================
CLOCK_THREAD_CPUTIME_ID Linux 3.2 1 ns ? CLOCK_THREAD_CPUTIME_ID Linux 3.2 1 ns 6 µs
CLOCK_THREAD_CPUTIME_ID FreeBSD 8.2 1 µs ? CLOCK_THREAD_CPUTIME_ID FreeBSD 8.2 1 µs 1 µs
GetThreadTimes() Windows Seven 15.6 ms ? GetThreadTimes() Windows Seven 16 ms ?
========================= ================ =============== =================== ========================= ================ =============== ===================
For CLOCK_THREAD_CPUTIME_ID, the precision of this table is the result For CLOCK_THREAD_CPUTIME_ID, the precision of this table is the result

8
pep-0418/clock_precision.py
View File

@ -24,11 +24,11 @@ def compute_precision(func):
def format_duration(dt): def format_duration(dt):
if dt >= 1e-3: if dt >= 1e-3:
return "%.1f ms" % (dt * 1e3) return "%.0f ms" % (dt * 1e3)
if dt >= 1e-6: if dt >= 1e-6:
return "%.1f µs" % (dt * 1e6) return "%.0f µs" % (dt * 1e6)
else: else:
return "%.1f ns" % (dt * 1e9) return "%.0f ns" % (dt * 1e9)
def test_clock(name, func): def test_clock(name, func):
precision = compute_precision(func) precision = compute_precision(func)
@ -42,7 +42,7 @@ for name in ('clock', 'perf_counter', 'process_time', 'monotonic', 'time'):
info = time.get_clock_info(name) info = time.get_clock_info(name)
if 'precision' in info: if 'precision' in info:
print("- announced precision: %s" % format_duration(info['precision'])) print("- announced precision: %s" % format_duration(info['precision']))
print("- function: %s" % info['function']) print("- implementation: %s" % info['implementation'])
print("- resolution: %s" % format_duration(info['resolution'])) print("- resolution: %s" % format_duration(info['resolution']))
clock_ids = [name for name in dir(time) if name.startswith("CLOCK_")] clock_ids = [name for name in dir(time) if name.startswith("CLOCK_")]