wall clock time

Discussion in 'C Programming' started by aegis, Dec 15, 2004.

  1. aegis

    aegis Guest

    What is wall clock time? the standard doesn't define it
    but I see its use in past posts on clc.



    --
    aegis
    aegis, Dec 15, 2004
    #1
    1. Advertising

  2. aegis

    Lew Pitcher Guest

    -----BEGIN PGP SIGNED MESSAGE-----
    Hash: SHA1

    aegis wrote:
    > What is wall clock time? the standard doesn't define it
    > but I see its use in past posts on clc.


    The term "Wall clock time" refers to the elapsed time that an activity
    takes, and alludes to the method of timing such an activity: look at the
    wall clock when the activity starts, look again when the activity ends,
    compute the difference between the two times.

    We use this term in contrast to "cpu time", which measures the elapsed
    time that an activity takes, excluding all the time the computer is not
    performing tasks for that activity (i.e. "data entry" time, etc.).

    - --

    Lew Pitcher, IT Consultant, Enterprise Data Systems
    Enterprise Technology Solutions, TD Bank Financial Group

    (Opinions expressed here are my own, not my employer's)
    -----BEGIN PGP SIGNATURE-----
    Version: GnuPG v1.2.4 (MingW32)

    iD8DBQFBwGpJagVFX4UWr64RArLiAJ9uccuWUUunxNjj2+E9gC6loQ2PYgCgyXrp
    6NlJdyt4BbThfSQ9yQvEvw4=
    =5AOQ
    -----END PGP SIGNATURE-----
    Lew Pitcher, Dec 15, 2004
    #2
    1. Advertising

  3. aegis

    Zoran Cutura Guest

    aegis <> wrote:
    > What is wall clock time? the standard doesn't define it
    > but I see its use in past posts on clc.


    Well its the time that your clock on the wall shows.
    There need not be any tool, function or else that provides
    your C programs with this information, system specific extensions make
    make this available.

    --
    Z ()
    "LISP is worth learning for the profound enlightenment experience
    you will have when you finally get it; that experience will make you
    a better programmer for the rest of your days." -- Eric S. Raymond
    Zoran Cutura, Dec 15, 2004
    #3
  4. aegis

    Mike Wahler Guest

    "aegis" <> wrote in message
    news:...
    > What is wall clock time?


    I don't know of any standardized meaning for it, but
    I'd guess it means 'local time'.

    > the standard doesn't define it


    Nope.

    > but I see its use in past posts on clc.


    Perhaps if you give context, we could figure out
    what the poster(s) meant.

    -Mike
    Mike Wahler, Dec 15, 2004
    #4
  5. >What is wall clock time? the standard doesn't define it
    >but I see its use in past posts on clc.


    The time according to a clock on a nearby wall, presuming it is
    properly set. This clock would be set according to the local time
    zone, and local daylight savings time conventions (if any). WHOSE
    wall may be an issue if the user and the system are in different
    time zones. A wall clock runs continuously, as distinguished from
    a stopwatch.

    A Football Game Clock runs only when plays are actually in progress,
    and not during timeouts and between plays. A CPU time clock runs
    only when the program is using the CPU. When a program is "using
    the CPU" is a bit system-specific, but on a multi-tasking system
    this generally does not include times the program is waiting for
    input, is waiting for disk I/O, paging, or swapping, or is not
    scheduled due to other programs running.

    Gordon L. Burditt
    Gordon Burditt, Dec 15, 2004
    #5
  6. "aegis"
    > What is wall clock time? the standard doesn't define it
    > but I see its use in past posts on clc.


    At the risk of making the same error twice in a day, I think wall clock time
    is OT as only the difference in time can be handled by C. Otherwise you're
    making a system call. If you stipulate any particular t1 then wall clock
    time is within the scope of ISO C. MPJ
    Merrill & Michele, Dec 15, 2004
    #6
  7. In article <>,
    Merrill & Michele <> wrote:

    > At the risk of making the same error twice in a day, I think wall clock time
    > is OT as only the difference in time can be handled by C.


    What about the standard C function time()?

    > Otherwise you're
    > making a system call.


    Why is a "system call" used by time() different than a "system call"
    used by printf()? A standard C function may, or may not, do one or
    more "system calls" but that is up to the implementation, i.e. it is
    outside of the standard.

    --
    Göran Larsson http://www.mitt-eget.com/
    Goran Larsson, Dec 15, 2004
    #7
  8. Zoran Cutura <> writes:
    > aegis <> wrote:
    >> What is wall clock time? the standard doesn't define it
    >> but I see its use in past posts on clc.

    >
    > Well its the time that your clock on the wall shows.
    > There need not be any tool, function or else that provides
    > your C programs with this information, system specific extensions make
    > make this available.


    See <time.h>. The time() function gives you a representation of what
    I'd refer to as "wall clock time" (as distinct from CPU time).

    I suppose "wall clock time" could refer either to a given moment or to
    an elapsed time; the latter can be computed by calling difftime().

    No system specific extensions are necessary, unless you need some
    particular resolution -- or unless you're using the phrase "wall clock
    time" to refer to something other than what I'm thinking of.

    --
    Keith Thompson (The_Other_Keith) <http://www.ghoti.net/~kst>
    San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
    We must do something. This is something. Therefore, we must do this.
    Keith Thompson, Dec 15, 2004
    #8
  9. On Wed, 15 Dec 2004 13:16:20 -0600, Merrill & Michele wrote:

    >
    > "aegis"
    >> What is wall clock time? the standard doesn't define it
    >> but I see its use in past posts on clc.

    >
    > At the risk of making the same error twice in a day, I think wall clock time
    > is OT as only the difference in time can be handled by C. Otherwise you're
    > making a system call. If you stipulate any particular t1 then wall clock
    > time is within the scope of ISO C. MPJ



    Wall clock time usually refers to time intervals. E.g. a program was
    running for 10 seconds and used 4 seconds of CPU time. The 10 seconds
    there is wall clock time, the 4 seconds isn't.

    Lawrence
    Lawrence Kirby, Dec 16, 2004
    #9

  10. > "Lawrence Kirby"
    > > Merrill & Michele wrote:

    >
    > >
    > > "aegis"
    > >> What is wall clock time? the standard doesn't define it
    > >> but I see its use in past posts on clc.

    > >
    > > At the risk of making the same error twice in a day, I think wall clock

    time
    > > is OT as only the difference in time can be handled by C. Otherwise

    you're
    > > making a system call. If you stipulate any particular t1 then wall

    clock
    > > time is within the scope of ISO C. MPJ

    >
    >
    > Wall clock time usually refers to time intervals. E.g. a program was
    > running for 10 seconds and used 4 seconds of CPU time. The 10 seconds
    > there is wall clock time, the 4 seconds isn't.


    What chapter is that in C Unleashed (you guys didn't do the greatest job of
    indexing. You did the bitshift stuff and I think a couple more, but the
    only way for me to really find anything in that book is sit down and slog
    through 400 pages. Maybe a cleaner presentation in version 2?)? MPJ
    Merrill & Michele, Dec 16, 2004
    #10
  11. On Thu, 16 Dec 2004 12:03:03 -0600, Merrill & Michele wrote:

    ....

    > What chapter is that in C Unleashed (you guys didn't do the greatest job of
    > indexing. You did the bitshift stuff and I think a couple more, but the
    > only way for me to really find anything in that book is sit down and slog
    > through 400 pages. Maybe a cleaner presentation in version 2?)? MPJ


    Well chapter 4 is about times and dates. I don't remember offhand if "wall
    clock time" is mentioned specifically. It could have been but it isn't a
    term that relates specifically to C.

    I'm sure the indexing could be improved, but don't forget the chapter list
    at the start. I don't see the need to slog through 400 pages to find
    relevant sections. :)

    Lawrence
    Lawrence Kirby, Dec 17, 2004
    #11
  12. "Lawrence Kirby"
    > Merrill & Michele wrote:
    >
    > ...
    >
    > > What chapter is that in C Unleashed (you guys didn't do the greatest job

    of
    > > indexing. You did the bitshift stuff and I think a couple more, but the
    > > only way for me to really find anything in that book is sit down and

    slog
    > > through 400 pages. Maybe a cleaner presentation in version 2?)? MPJ

    >
    > Well chapter 4 is about times and dates. I don't remember offhand if "wall
    > clock time" is mentioned specifically. It could have been but it isn't a
    > term that relates specifically to C.
    >
    > I'm sure the indexing could be improved, but don't forget the chapter list
    > at the start. I don't see the need to slog through 400 pages to find
    > relevant sections. :)


    The whole point of a reference text is that you HAVE FORGOTTEN the contents.
    Merry Christmas, Lawrence. If you talk to Mr. Heathfield, tell him that C
    dreams. MPJ
    Merrill & Michele, Dec 18, 2004
    #12
  13. aegis

    infobahn Guest

    Merrill & Michele wrote:
    > "Lawrence Kirby"
    >
    >>Well chapter 4 is about times and dates. I don't remember offhand if "wall
    >>clock time" is mentioned specifically. It could have been but it isn't a
    >>term that relates specifically to C.


    It gets a passing mention on page 123, as a cursory inspection of the
    relevant chapter will reveal. I found it from scratch in about eight
    seconds, so it was no real hardship that the term didn't appear in the
    index.

    >>
    >>I'm sure the indexing could be improved, but don't forget the chapter list
    >>at the start. I don't see the need to slog through 400 pages to find
    >>relevant sections. :)

    >
    >
    > The whole point of a reference text is that you HAVE FORGOTTEN the contents.


    "C Unleashed" is not a reference text.
    infobahn, Dec 18, 2004
    #13
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Peter Hansen
    Replies:
    13
    Views:
    665
    Peter Hansen
    Jul 7, 2005
  2. Coates, Steve (ACHE)

    RE: Determining actual elapsed (wall-clock) time

    Coates, Steve (ACHE), Jul 4, 2005, in forum: Python
    Replies:
    2
    Views:
    375
    Roy Smith
    Jul 4, 2005
  3. Geert Jansen
    Replies:
    1
    Views:
    318
    Dieter Maurer
    Nov 26, 2005
  4. Replies:
    5
    Views:
    1,523
    Ben Bacarisse
    Nov 19, 2006
  5. Replies:
    1
    Views:
    650
    James Kanze
    Oct 18, 2008
Loading...

Share This Page