[Development] More on QDateTime / QTimeZone

[John Layt]

On Saturday 14 Sep 2013 03:04:45 John Layt wrote:
> * Rather strangely timeSpec() is 30% slower despite now only returning the
> member directly instead of having to do a switch based on the member, a few
> other calls are equally confusing.

Ah, stupid me, I was including the creation in the timings, remove that and 
they're the same or faster.  Here's some revised numbers for just the 
functions themselves, as before 3650 different dates per iteration:

Action                      Base    Msecs   %
create():                   0.299   0.418   40
isNull():                   0.082   0.103   26
isValid():                  0.087   0.152   75
date():                     0.060   0.290  383
time():                     0.060   0.292  387
offsetFromUtc():            6.929   8.242   19
toMSecsSinceEpoch():        6.256   8.201   31
toMSecsSinceEpoch1950():    7.065   3.262  -54
toMSecsSinceEpoch2050():    8.143   9.983   23
setDate():                  0.449   0.814   81
setTime():                  0.428   0.812   90
setMSecsSinceEpoch():       6.512   3.971  -39
addDays():                  0.456   0.828   82
addMonths():                1.598   1.989   24
addYears():                 1.574   1.965   25
addMSecs():                12.600   9.766  -22
toTimeSpec():               6.642   8.647   30
toOffsetFromUtc():          6.983   8.691   24
daysTo():                   0.117   0.603  415
msecsTo():                 12.850  16.660   30
equivalentDiffSpec():       6.290   8.089   29
lessThanDiffSpec():         6.288   8.054   28
currentDateTime():          1.110   0.315  -72
fromMSecsSinceEpoch():      6.083   2.462  -60

As I said, I'm testing a speed-up for toMSecsSinceEpoch() which makes it 
faster than the old version, which feeds through to most of the other slower 
functions.  I'll also have a look at date() and time() for improvements which 
will also improve things like daysTo(), but they will always be slower now.

One other note, these are only after the msecs change, adding in the "missing 
hour" fix has a marginal effect except on toValid() which balloons out to 
8.576 as it has to check the tz now.

John.