Cheers,use strict; use warnings; use Math::GMPz qw(:mpz); use Time::HiRes; use Inline C => Config => USING => 'ParseRegExp', BUILD_NOISY => 1, INC => '-IC:/MinGW/msys/1.0/local/include', LIBS => '-LC:/MinGW/msys/1.0/local/lib -lgmp', TYPEMAPS => './typemap', # ships with Math::GMPz ; use Inline C => <<'EOC'; #include <gmp.h> int start(mpz_t * haystack, int haystack_size, mpz_t * needle, int needle_size) { int h_bit, n_bit, nless1 = needle_size -1; for(h_bit = nless1; h_bit < haystack_size; h_bit++) { for(n_bit = 0; n_bit < needle_size; n_bit++) { if(mpz_tstbit(*haystack, h_bit - needle_size + n_bit) != mpz_tstbit(needle, n_bit)) break; if(n_bit == nless1) return h_bit; } } return 0; } EOC my ($t1, $t2, $match); my ($haystack_size, $needle_size) = (250e6, 1e6); # generate the haystack - takes a while my $h_string = rstring($haystack_size); # generate a needle that's guaranteed to match , starting # at 19 bits from the lh end - ie at bit 249999981 my $n_string = substr($h_string, 19, $needle_size); # create the haystack gmp vector. (We need an additional # leading "1" bit to ensure that leading zero bits aren't ignored.) my $haystack = Math::GMPz->new( "1" . $h_string , 2); # create the needle gmp vector. (We need an additional # leading "1" bit to ensure that leading zero bits aren't ignored.) my $needle = Math::GMPz->new("1" . $n_string, 2); # Check that we've got the right number of bits. print Rmpz_sizeinbase($haystack, 2), " ", Rmpz_sizeinbase($needle, 2), "\n"; $t1 = Time::HiRes::time(); $match = start($haystack, $haystack_size, $needle, $needle_size); $t2 = Time::HiRes::time(); print $match, " ", $t2 - $t1, "\n"; sub rstring { die "haystack size must be a multiple of 10" if $_[0] % 10; my $ret; my $its = $_[0] / 10; $ret .= sprintf("%010b",int rand 1024) for 1 .. $its; if(length($ret) != $_[0] || $ret =~ /[^01]/) { die "Error in sub rstring"; } return $ret; } # Outputs: # 250000001 1000001 # 249999981 3.16680598258972
In reply to Re^3: [OT] The interesting problem of comparing bit-strings.
by syphilis
in thread [OT] The interesting problem of comparing bit-strings.
by BrowserUk
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