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RE: (tye)RE: The Best Infinite Loop

by rdw (Curate)
 on Oct 17, 2000 at 14:23 UTC ( #37117=note: print w/replies, xml ) Need Help??

in reply to (tye)RE: The Best Infinite Loop
in thread The Best Infinite Loop

So I tried it (with Deparse)...

```while ()  { \$_++; last if \$_ == 1000; }
while (1) { \$_++; last if \$_ == 1000; }
for (;;)  { \$_++; last if \$_ == 1000; }
`perl -MO=Deparse test.pl`
```for (;;) {
++\$_;
last if \$_ == 1000;
}
for (;;) {
++\$_;
last if \$_ == 1000;
}
for (;;) {
++\$_;
last if \$_ == 1000;
}
test.pl syntax OK

So they should be all the same speed. I'm with tye on this one - I'll be sticking with with while(1) since I think it looks nicer.

Have fun,

rdw

Replies are listed 'Best First'.
RE: RE: (tye)RE: The Best Infinite Loop
by BlaisePascal (Monk) on Oct 18, 2000 at 02:16 UTC
Those three parse the same, but the block loops don't parse that way. In fact, there are at least three different ways to do an infinite loop with redo that parse differently... So I modified tye's benchmark, and got:
```#!/usr/bin/perl -w

use strict;
use Benchmark;

timethese( 1000,
{
'0while' => sub { \$_ = 0; while (1)   { \$_++; last if (\$_ == 10000)
+; } },
'0for'   => sub { \$_ = 0; for   (;;)  { \$_++; last if (\$_ == 10000)
+; } },
'0redo1' => sub { \$_ = 0;   { \$_++; redo if     (\$_ <  10000);
+  } },
'0redo2' => sub { \$_ = 0;   { \$_++; redo unless (\$_ == 10000);
+  } },
'0redo3' => sub { \$_ = 0;   { \$_++; last if     (\$_ == 10000); redo
+; } },
'1while' => sub { \$_ = 0; while (1)   { \$_++; last if (\$_ == 10000)
+; } },
'1for'   => sub { \$_ = 0; for   (;;)  { \$_++; last if (\$_ == 10000)
+; } },
'1redo1' => sub { \$_ = 0;   { \$_++; redo if     (\$_ <  10000);
+  } },
'1redo2' => sub { \$_ = 0;   { \$_++; redo unless (\$_ == 10000);
+  } },
'1redo3' => sub { \$_ = 0;   { \$_++; last if     (\$_ == 10000); redo
+; } },
});
__END__
Benchmark: timing 1000 iterations of 0for, 0redo1, 0redo2, 0redo3, 0wh
+ile, 1for, 1redo1, 1redo2, 1redo3, 1while...
0for: 14 wallclock secs (11.43 usr +  0.00 sys = 11.43 CPU)
0redo1: 14 wallclock secs (11.62 usr +  0.00 sys = 11.62 CPU)
0redo2: 15 wallclock secs (12.68 usr +  0.00 sys = 12.68 CPU)
0redo3: 15 wallclock secs (12.36 usr +  0.00 sys = 12.36 CPU)
0while: 14 wallclock secs (11.48 usr +  0.00 sys = 11.48 CPU)
1for: 13 wallclock secs (11.40 usr +  0.00 sys = 11.40 CPU)
1redo1: 14 wallclock secs (11.63 usr +  0.00 sys = 11.63 CPU)
1redo2: 14 wallclock secs (11.54 usr +  0.00 sys = 11.54 CPU)
1redo3: 15 wallclock secs (12.36 usr +  0.01 sys = 12.37 CPU)
1while: 14 wallclock secs (11.42 usr +  0.00 sys = 11.42 CPU)
I don't know why the difference in times between the first run and the second...

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