Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw
 
PerlMonks  

comment on

( [id://3333]=superdoc: print w/replies, xml ) Need Help??

The optomiser eliminates any differences. Yours (c_luhn3 below) can be slightly faster one run and slightly slower on the next; but the difference is less that 0.5% either way:

#! perl -slw use strict; use Inline C => Config => BUILD_NOISY => 1; use Inline C => <<'END_C', NAME => '_luhn', CLEAN_AFTER_BUILD =>0; int c_luhn( char *s ) { int i, total = 0; for( i=0; i < 15; ++i ) { int d = s[ i ] - '0'; if( !( i & 1 ) ) { d *= 2; if( d > 9 ) d -= 9; } total += d; } total *= 9; return total % 10; } int l[] = { 0, 2, 4, 6, 8, 1, 3, 5, 7, 9 }; int c_luhn2( char *s ) { int total = 0; total += l[ s[ 0] - '0' ]; total += s[ 1] - '0'; total += l[ s[ 2] - '0' ]; total += s[ 3] - '0'; total += l[ s[ 4] - '0' ]; total += s[ 5] - '0'; total += l[ s[ 6] - '0' ]; total += s[ 7] - '0'; total += l[ s[ 8] - '0' ]; total += s[ 9] - '0'; total += l[ s[10] - '0' ]; total += s[11] - '0'; total += l[ s[12] - '0' ]; total += s[13] - '0'; total += l[ s[14] - '0' ]; total *= 9; return total % 10; } int ll[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 6, 8, 1, 3, 5, 7, 9 }; int c_luhn3( char *s ) { return (( ll[ (int)s[ 0] ] + s[ 1] + ll[ (int)s[ 2] ] + s[ 3] + ll[ (int)s[ 4] ] + s[ 5] + ll[ (int)s[ 6] ] + s[ 7] + ll[ (int)s[ 8] ] + s[ 9] + ll[ (int)s[10] ] + s[11] + ll[ (int)s[12] ] + s[13] + ll[ (int)s[14] ] - 7 * '0' ) * 9) % 10; } END_C use Time::HiRes qw[ time ]; my @samples = qw[ 4011350000000008 4011350000000016 4011350000000024 4011350000000032 4011350000000040 4011350000000057 4011350000000065 4011350000000073 4011350000000081 4011350000000099 ]; sub luhn { use integer; my $s = $_[ 0 ]; my $total = 0; for my $i ( 0 .. 14 ) { my $d = substr( $s, $i, 1 ); unless( $i & 1 ) { $d *= 2; $d -= 9 if $d > 9; } $total += $d; } $total *= 9; return chop $total; } for ( @samples ) { print "$_: ", luhn( substr $_, 0, 15 ); } my $start = time; #for ( 401135000000000..401135000999999 ) { # my $chk = luhn( $_ ); #} #printf "Took %.9f seconds.\n", time() - $start; #for ( @samples ) { # print "$_: ", c_luhn( $_ ); #} $start = time; for ( 401135000000000..401135000999999 ) { my $chk = c_luhn( $_ ); } printf "Took %.9f seconds.\n", time() - $start; for ( @samples ) { print "$_: ", c_luhn2( $_ ); } $start = time; for ( 401135000000000..401135000999999 ) { my $chk = c_luhn2( $_ ); } printf "Took %.9f seconds.\n", time() - $start; for ( @samples ) { print "$_: ", c_luhn3( $_ ); } $start = time; for ( 401135000000000..401135000999999 ) { my $chk = c_luhn3( $_ ); } printf "Took %.9f seconds.\n", time() - $start;
C:\test>luhn 4011350000000008: 8 4011350000000016: 6 4011350000000024: 4 4011350000000032: 2 4011350000000040: 0 4011350000000057: 7 4011350000000065: 5 4011350000000073: 3 4011350000000081: 1 4011350000000099: 9 Took 0.751899958 seconds. 4011350000000008: 8 4011350000000016: 6 4011350000000024: 4 4011350000000032: 2 4011350000000040: 0 4011350000000057: 7 4011350000000065: 5 4011350000000073: 3 4011350000000081: 1 4011350000000099: 9 Took 0.695394039 seconds. 4011350000000008: 8 4011350000000016: 6 4011350000000024: 4 4011350000000032: 2 4011350000000040: 0 4011350000000057: 7 4011350000000065: 5 4011350000000073: 3 4011350000000081: 1 4011350000000099: 9 Took 0.693738222 seconds. C:\test>luhn 4011350000000008: 8 4011350000000016: 6 4011350000000024: 4 4011350000000032: 2 4011350000000040: 0 4011350000000057: 7 4011350000000065: 5 4011350000000073: 3 4011350000000081: 1 4011350000000099: 9 Took 0.751657963 seconds. 4011350000000008: 8 4011350000000016: 6 4011350000000024: 4 4011350000000032: 2 4011350000000040: 0 4011350000000057: 7 4011350000000065: 5 4011350000000073: 3 4011350000000081: 1 4011350000000099: 9 Took 0.694734097 seconds. 4011350000000008: 8 4011350000000016: 6 4011350000000024: 4 4011350000000032: 2 4011350000000040: 0 4011350000000057: 7 4011350000000065: 5 4011350000000073: 3 4011350000000081: 1 4011350000000099: 9 Took 0.697062969 seconds.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
In the absence of evidence, opinion is indistinguishable from prejudice. Suck that fhit

In reply to Re^8: Faster Luhn Check Digit Calculation? by BrowserUk
in thread Faster Luhn Check Digit Calculation? by kschwab

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":



  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or How to display code and escape characters are good places to start.
Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Chatterbox?
and the web crawler heard nothing...

How do I use this?Last hourOther CB clients
Other Users?
Others wandering the Monastery: (3)
As of 2024-03-28 18:05 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    No recent polls found