Tcl Documentation > Tcl Commands > timerate

Tcl Applications | Tcl Commands | Tcl C API

NAME

timerate — Calibrated performance measurements of script execution time

SYNOPSIS

DESCRIPTION

-calibrate

-overhead double

-direct

EXAMPLES

SEE ALSO

KEYWORDS

NAME

SYNOPSIS

DESCRIPTION

The first and second form will evaluate script until the interval time given in milliseconds elapses, or for 1000 milliseconds (1 second) if time is not specified.

The parameter max-count could additionally impose a further restriction by the maximal number of iterations to evaluate the script. If max-count is specified, the evalution will stop either this count of iterations is reached or the time is exceeded.

It will then return a canonical tcl-list of the form:

0.095977 µs/# 52095836 # 10419167 #/sec 5000.000 net-ms

which indicates:

• the average amount of time required per iteration, in microseconds ([lindex $result 0])
• the count how many times it was executed ([lindex $result 2])
• the estimated rate per second ([lindex $result 4])
• the estimated real execution time without measurement overhead ([lindex $result 6])

The following options may be supplied to the timerate command:

-calibrate

To measure very fast scripts as exactly as possible, a calibration process may be required. The -calibrate option is used to calibrate timerate itself, calculating the estimated overhead of the given script as the default overhead for future invocations of the timerate command. If the time parameter is not specified, the calibrate procedure runs for up to 10 seconds.

Note that calibration is not thread safe in the current implementation.

-overhead double

The -overhead parameter supplies an estimate (in microseconds) of the measurement overhead of each iteration of the tested script. This quantity will be subtracted from the measured time prior to reporting results. This can be useful for removing the cost of interpreter state reset commands from the script being measured.

-direct

The -direct option causes direct execution of the supplied script, without compilation, in a manner similar to the time command. It can be used to measure the cost of Tcl_EvalObjEx, of the invocation of canonical lists, and of the uncompiled versions of bytecoded commands.

As opposed to the time commmand, which runs the tested script for a fixed number of iterations, the timerate command runs it for a fixed time. Additionally, the compiled variant of the script will be used during the entire measurement, as if the script were part of a compiled procedure, if the -direct option is not specified. The fixed time period and possibility of compilation allow for more precise results and prevent very long execution times by slow scripts, making it practical for measuring scripts with highly uncertain execution times.

EXAMPLES

# calibrate
timerate -calibrate {}

# measure
timerate { for {set i 0} {$i<10} {incr i} {} } 5000

Estimate how fast it takes for a simple Tcl for loop, ignoring the overhead of the management of the variable that controls the loop:

# calibrate for overhead of variable operations
set i 0; timerate -calibrate {expr {$i<10}; incr i} 1000

# measure
timerate {
    for {set i 0} {$i<10} {incr i} {}
} 5000

Estimate the speed of calculating the hour of the day using clock format only, ignoring overhead of the portion of the script that prepares the time for it to calculate:

# calibrate
timerate -calibrate {}

# estimate overhead
set tm 0
set ovh [lindex [timerate {
    incr tm [expr {24*60*60}]
}] 0]

# measure using estimated overhead
set tm 0
timerate -overhead $ovh {
    clock format $tm -format %H
    incr tm [expr {24*60*60}]; # overhead for this is ignored
} 5000

SEE ALSO

KEYWORDS