[Python-checkins] peps: PEP 418: Add a table summarizing system clocks

[victor.stinner]

http://hg.python.org/peps/rev/215b14945a3f
changeset:   4175:215b14945a3f
user:        Victor Stinner <victor.stinner at gmail.com>
date:        Fri Mar 30 23:16:06 2012 +0200
summary:
  PEP 418: Add a table summarizing system clocks

files:
  pep-0418.txt |  41 +++++++++++++++++++++++++++++++++++----
  1 files changed, 36 insertions(+), 5 deletions(-)


diff --git a/pep-0418.txt b/pep-0418.txt
--- a/pep-0418.txt
+++ b/pep-0418.txt
@@ -185,20 +185,25 @@
 
 Table summarizing all monotonic clocks:
 
-
 ========================= =============== =============== ================ ====================
 Name                      Resolution      Accuracy        Adjusted by NTP? Action on suspend
 ========================= =============== =============== ================ ====================
-CLOCK_MONOTONIC_RAW       1 ns            ?               No               Stopped
-gethrtime                 1 ns            ?               No               Not stopped
+CLOCK_MONOTONIC_RAW       1 ns            (*)             No               Stopped
+gethrtime                 1 ns            (*)             No               Not stopped
+CLOCK_HIGHRES             1 ns            (*)             No               ?
+CLOCK_MONOTONIC           1 ns            (*)             Yes on Linux     Stopped on Linux
 mach_absolute_time()      1 ns            ?               No               ?
-CLOCK_HIGHRES             1 ns            ?               No               ?
-CLOCK_MONOTONIC           1 ns            ?               Yes on Linux     Stopped on Linux
 QueryPerformanceCounter() \-              0.3 ns - 5 ns   No               Accuracy issue
 GetTickCount[64]()        1 ms            1 ms - 15 ms    No               Include suspend time
 timeGetTime()             1 ms            1 ms - 15 ms    No               ?
 ========================= =============== =============== ================ ====================
 
+(*) The accurary of monotonic clocks depends on the operating system.
+
+ * Linux: ?
+ * FreeBSD: ?
+ * Solaris: ?
+
 The resolution is the smallest difference between two timestamps supported by
 the format used by the clock. For example, clock_gettime() uses a timespec
 structure which has two integer fileds, tv_sec and tv_nsec, so the resolution
@@ -401,6 +406,32 @@
 System time
 -----------
 
+The system time can be set manually by the system administrator or
+automatically by a NTP daemon.
+
+Summary
+^^^^^^^
+
+Table summarizing all system time clocks:
+
+========================= =============== ===============
+Name                      Resolution      Accuracy
+========================= =============== ===============
+CLOCK_REALTIME            1 ns            (*)
+GetSystemTimeAsFileTime   100 ns          1 ms - 15 ms
+gettimeofday()            1 µs            (*)
+ftime()                   1 ms            (*)
+time()                    1 sec           1 sec
+========================= =============== ===============
+
+(*) The accurary of system clocks depends on the operating system.
+
+ * Windows: 1 ms - 15 ms
+ * Linux: ?
+ * Mac OS X: ?
+ * FreeBSD: ?
+
+
 Windows: GetSystemTimeAsFileTime
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

-- 
Repository URL: http://hg.python.org/peps