wall clock time

[aegis]

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

 

[Lew Pitcher]

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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)
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[Zoran Cutura]

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.

 

[Mike Wahler]

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

 

[Gordon Burditt]

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

 

[Merrill & Michele]

"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

 

[Goran Larsson]

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.

 

[Keith Thompson]

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.

 

[Lawrence Kirby]

"aegis"

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

 

[Merrill & Michele]

"Lawrence Kirby"


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

 

[Lawrence Kirby]

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

 

[Merrill & Michele]

"Lawrence Kirby"

Merrill & Michele wrote:

...


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

 

[infobahn]

"Lawrence Kirby"

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.

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

"C Unleashed" is not a reference text.