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INNER {returnImm {Unknow state transition: LINE -> END} {}} CALL {my render_wikit Time {'''`[http://tcl.tk/man/tcl/TclCmd/time.htm%|%time]`''' a [Tcl Commands%|%built-in] Tcl command, repeatedly executes a [script], and reports
elapsed time.



** Synopsis **

    :   '''time''' ''script'' ?''iterations''?



** Description **

'''`time`''' executes ''script'' one time, or optionally, ''iterations'' times,
and reports the average elapsed time per iteration.  Since Tcl version [Changes
in Tcl/Tk 8.5%|%8.5], elapsed time has sub-microsecond resolution,  with
accuracy depending on the timers available from the [operating system%|%OS].

'''Example:'''

======
time {myCommand $arg1 $arg2} 1000
======

, which executes the script 1000 times, and returns a list like this:

 123456 microseconds per iteration


More iterations increase the precision of the returned value, at the cost of
longer execution of `time`.


You can measure the runtime of a lengthy script with the following pattern:

======
set t0 [clock clicks -millisec]
...
...
puts stderr "[expr {([clock clicks -millisec]-$t0)/1000.}] sec" ;# RS
======

[kbk], Tcl's own wizard of speed and time,  has done all the work to ensure



[DKF]: It's not always easy to pick a good number of iterations to run the timing script for. This script picks a balance by trying to use the number of iterations that would take about 2 seconds (subject to it being a minimum of 500 iterations)

Explanation:  The script first tries to factor out the compilation time, then does an initial timing run to estimate the number of iterations for the main run.
======
proc measure args {
    set it [expr {int(ceil(10000./[lindex [time $args] 0]))}]
    set it [expr {int(ceil(2000000./[lindex [time $args $it] 0]))}]
    while {$it < 500} {set it 500}
    lindex [time $args $it] 0
}
======

Use it like this:

======
measure theProc arg1 arg2...
======

Adapting to take a single script argument instead is trivial.



** Novel Uses of Time **

Even when you're not interested in the timing, you can use `time` as a simple control structure for loops:

======
time {puts Hello} 5
======

instead of

======
for {set i 0} {$i<5} {incr i} {puts Hello}
 for {set i 0} {$i<5} {incr i} {puts Hello}

([MS] voip in the [Tcl chatroom] 2005-03-03, brought here by [RS])


[sergiol]
I use this approach as a code shortener, when I am doing code golf, as I state in https://codegolf.stackexchange.com/a/126236/29325 with a '''GOTCHA''':

[LV]: Sometimes users ask how to get a tcl program's time in terms of real/user/system, similar to how they would use the ksh built in time command.
The command documented on this page doesn't provide information of that granularity. Does anyone know of alternative methods?

----

[AMG], adapted from an email by [MS]:

"`time` has more looping overhead than a script version!  See below for proof."

======
proc f {} {}

proc a {} {
    set n 100000
    puts [time f $n]

    set c $n
    incr c
    set start [clock microseconds]
    while {[incr c -1]} {
        f
    }
    set end [clock microseconds]

    puts "[expr {($end - $start)/double($n)}] microseconds per iteration"
}

a
======

On my machine (WinXP, Tcl 8.6b1.2), this produces the following times:

======
3.78325 microseconds per iteration
1.62831 microseconds per iteration
======

`f` is run 100,000 times, both by `time` and by `[while]`/`[incr]`.  Strangely enough, it takes `time` more than twice as long as `while` to do this.  That makes no sense.  Maybe `time` is recompiling the script `f` each time.  But, how long can it take to compile a script that's only '''one character long'''???




** See Also **

    [How to measure Performance]:    Additional info - but no obvious examples.



** Disambiguation **

Another use of the word ''time'' is as a network protocol for the transmission of time data - see RFC868 [http://www.faqs.org/rfcs/rfc868.html]
[NTP] is a more sophisticated protocol, but the time protocol does a simple job simply.


In yet another different use of the word '''time''', [LV] asks "Has anyone written a ''time'' chooser similar to the date chooser widgets written elsewhere on the Wiki?" Larry refers to [A little date chooser] and [An i15d date chooser].

You might like to check out: [timeentry] and [timefield].



----} regexp2} CALL {my render Time {'''`[http://tcl.tk/man/tcl/TclCmd/time.htm%|%time]`''' a [Tcl Commands%|%built-in] Tcl command, repeatedly executes a [script], and reports
elapsed time.



** Synopsis **

    :   '''time''' ''script'' ?''iterations''?



** Description **

'''`time`''' executes ''script'' one time, or optionally, ''iterations'' times,
and reports the average elapsed time per iteration.  Since Tcl version [Changes
in Tcl/Tk 8.5%|%8.5], elapsed time has sub-microsecond resolution,  with
accuracy depending on the timers available from the [operating system%|%OS].

'''Example:'''

======
time {myCommand $arg1 $arg2} 1000
======

, which executes the script 1000 times, and returns a list like this:

 123456 microseconds per iteration


More iterations increase the precision of the returned value, at the cost of
longer execution of `time`.


You can measure the runtime of a lengthy script with the following pattern:

======
set t0 [clock clicks -millisec]
...
...
puts stderr "[expr {([clock clicks -millisec]-$t0)/1000.}] sec" ;# RS
======

[kbk], Tcl's own wizard of speed and time,  has done all the work to ensure



[DKF]: It's not always easy to pick a good number of iterations to run the timing script for. This script picks a balance by trying to use the number of iterations that would take about 2 seconds (subject to it being a minimum of 500 iterations)

Explanation:  The script first tries to factor out the compilation time, then does an initial timing run to estimate the number of iterations for the main run.
======
proc measure args {
    set it [expr {int(ceil(10000./[lindex [time $args] 0]))}]
    set it [expr {int(ceil(2000000./[lindex [time $args $it] 0]))}]
    while {$it < 500} {set it 500}
    lindex [time $args $it] 0
}
======

Use it like this:

======
measure theProc arg1 arg2...
======

Adapting to take a single script argument instead is trivial.



** Novel Uses of Time **

Even when you're not interested in the timing, you can use `time` as a simple control structure for loops:

======
time {puts Hello} 5
======

instead of

======
for {set i 0} {$i<5} {incr i} {puts Hello}
 for {set i 0} {$i<5} {incr i} {puts Hello}

([MS] voip in the [Tcl chatroom] 2005-03-03, brought here by [RS])


[sergiol]
I use this approach as a code shortener, when I am doing code golf, as I state in https://codegolf.stackexchange.com/a/126236/29325 with a '''GOTCHA''':

[LV]: Sometimes users ask how to get a tcl program's time in terms of real/user/system, similar to how they would use the ksh built in time command.
The command documented on this page doesn't provide information of that granularity. Does anyone know of alternative methods?

----

[AMG], adapted from an email by [MS]:

"`time` has more looping overhead than a script version!  See below for proof."

======
proc f {} {}

proc a {} {
    set n 100000
    puts [time f $n]

    set c $n
    incr c
    set start [clock microseconds]
    while {[incr c -1]} {
        f
    }
    set end [clock microseconds]

    puts "[expr {($end - $start)/double($n)}] microseconds per iteration"
}

a
======

On my machine (WinXP, Tcl 8.6b1.2), this produces the following times:

======
3.78325 microseconds per iteration
1.62831 microseconds per iteration
======

`f` is run 100,000 times, both by `time` and by `[while]`/`[incr]`.  Strangely enough, it takes `time` more than twice as long as `while` to do this.  That makes no sense.  Maybe `time` is recompiling the script `f` each time.  But, how long can it take to compile a script that's only '''one character long'''???




** See Also **

    [How to measure Performance]:    Additional info - but no obvious examples.



** Disambiguation **

Another use of the word ''time'' is as a network protocol for the transmission of time data - see RFC868 [http://www.faqs.org/rfcs/rfc868.html]
[NTP] is a more sophisticated protocol, but the time protocol does a simple job simply.


In yet another different use of the word '''time''', [LV] asks "Has anyone written a ''time'' chooser similar to the date chooser widgets written elsewhere on the Wiki?" Larry refers to [A little date chooser] and [An i15d date chooser].

You might like to check out: [timeentry] and [timefield].



----}} CALL {my revision Time} CALL {::oo::Obj1271409 process revision/Time} CALL {::oo::Obj1271407 process}

-errorcode

NONE

-errorinfo

Unknow state transition: LINE -> END
    while executing
"error $msg"
    (class "::Wiki" method "render_wikit" line 6)
    invoked from within
"my render_$default_markup $N $C $mkup_rendering_engine"
    (class "::Wiki" method "render" line 8)
    invoked from within
"my render $name $C"
    (class "::Wiki" method "revision" line 31)
    invoked from within
"my revision $page"
    (class "::Wiki" method "process" line 56)
    invoked from within
"$server process [string trim $uri /]"

-errorline

4