benchmark.3

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.\" ========================================================================
.\"
.IX Title "Benchmark 3"
.TH Benchmark 3 "2007-12-18" "perl v5.10.0" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Benchmark \- benchmark running times of Perl code
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Benchmark qw(:all) ;
\&
\&    timethis ($count, "code");
\&
\&    # Use Perl code in strings...
\&    timethese($count, {
\&        \*(AqName1\*(Aq => \*(Aq...code1...\*(Aq,
\&        \*(AqName2\*(Aq => \*(Aq...code2...\*(Aq,
\&    });
\&
\&    # ... or use subroutine references.
\&    timethese($count, {
\&        \*(AqName1\*(Aq => sub { ...code1... },
\&        \*(AqName2\*(Aq => sub { ...code2... },
\&    });
\&
\&    # cmpthese can be used both ways as well
\&    cmpthese($count, {
\&        \*(AqName1\*(Aq => \*(Aq...code1...\*(Aq,
\&        \*(AqName2\*(Aq => \*(Aq...code2...\*(Aq,
\&    });
\&
\&    cmpthese($count, {
\&        \*(AqName1\*(Aq => sub { ...code1... },
\&        \*(AqName2\*(Aq => sub { ...code2... },
\&    });
\&
\&    # ...or in two stages
\&    $results = timethese($count, 
\&        {
\&            \*(AqName1\*(Aq => sub { ...code1... },
\&            \*(AqName2\*(Aq => sub { ...code2... },
\&        },
\&        \*(Aqnone\*(Aq
\&    );
\&    cmpthese( $results ) ;
\&
\&    $t = timeit($count, \*(Aq...other code...\*(Aq)
\&    print "$count loops of other code took:",timestr($t),"\en";
\&
\&    $t = countit($time, \*(Aq...other code...\*(Aq)
\&    $count = $t\->iters ;
\&    print "$count loops of other code took:",timestr($t),"\en";
\&
\&    # enable hires wallclock timing if possible
\&    use Benchmark \*(Aq:hireswallclock\*(Aq;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The Benchmark module encapsulates a number of routines to help you
figure out how long it takes to execute some code.
.PP
timethis \- run a chunk of code several times
.PP
timethese \- run several chunks of code several times
.PP
cmpthese \- print results of timethese as a comparison chart
.PP
timeit \- run a chunk of code and see how long it goes
.PP
countit \- see how many times a chunk of code runs in a given time
.Sh "Methods"
.IX Subsection "Methods"
.IP "new" 10
.IX Item "new"
Returns the current time.   Example:
.Sp
.Vb 6
\&    use Benchmark;
\&    $t0 = new Benchmark;
\&    # ... your code here ...
\&    $t1 = new Benchmark;
\&    $td = timediff($t1, $t0);
\&    print "the code took:",timestr($td),"\en";
.Ve
.IP "debug" 10
.IX Item "debug"
Enables or disable debugging by setting the \f(CW$Benchmark::Debug\fR flag:
.Sp
.Vb 3
\&    debug Benchmark 1;
\&    $t = timeit(10, \*(Aq 5 ** $Global \*(Aq);
\&    debug Benchmark 0;
.Ve
.IP "iters" 10
.IX Item "iters"
Returns the number of iterations.
.Sh "Standard Exports"
.IX Subsection "Standard Exports"
The following routines will be exported into your namespace
if you use the Benchmark module:
.IP "timeit(\s-1COUNT\s0, \s-1CODE\s0)" 10
.IX Item "timeit(COUNT, CODE)"
Arguments: \s-1COUNT\s0 is the number of times to run the loop, and \s-1CODE\s0 is
the code to run.  \s-1CODE\s0 may be either a code reference or a string to
be eval'd; either way it will be run in the caller's package.
.Sp
Returns: a Benchmark object.
.IP "timethis ( \s-1COUNT\s0, \s-1CODE\s0, [ \s-1TITLE\s0, [ \s-1STYLE\s0 ]] )" 10
.IX Item "timethis ( COUNT, CODE, [ TITLE, [ STYLE ]] )"
Time \s-1COUNT\s0 iterations of \s-1CODE\s0. \s-1CODE\s0 may be a string to eval or a
code reference; either way the \s-1CODE\s0 will run in the caller's package.
Results will be printed to \s-1STDOUT\s0 as \s-1TITLE\s0 followed by the times.
\&\s-1TITLE\s0 defaults to \*(L"timethis \s-1COUNT\s0\*(R" if none is provided. \s-1STYLE\s0
determines the format of the output, as described for \fItimestr()\fR below.
.Sp
The \s-1COUNT\s0 can be zero or negative: this means the \fIminimum number of
\&\s-1CPU\s0 seconds\fR to run.  A zero signifies the default of 3 seconds.  For
example to run at least for 10 seconds:
.Sp
.Vb 1
\&        timethis(\-10, $code)
.Ve
.Sp
or to run two pieces of code tests for at least 3 seconds:
.Sp
.Vb 1
\&        timethese(0, { test1 => \*(Aq...\*(Aq, test2 => \*(Aq...\*(Aq})
.Ve
.Sp
\&\s-1CPU\s0 seconds is, in \s-1UNIX\s0 terms, the user time plus the system time of
the process itself, as opposed to the real (wallclock) time and the
time spent by the child processes.  Less than 0.1 seconds is not
accepted (\-0.01 as the count, for example, will cause a fatal runtime
exception).
.Sp
Note that the \s-1CPU\s0 seconds is the \fBminimum\fR time: \s-1CPU\s0 scheduling and
other operating system factors may complicate the attempt so that a
little bit more time is spent.  The benchmark output will, however,
also tell the number of \f(CW$code\fR runs/second, which should be a more
interesting number than the actually spent seconds.
.Sp