Merge remote-tracking branch 'upstream/master'

37 files changed, 2260 insertions, 1583 deletions

diff --git a/challenge-168/cheok-yin-fung/perl/ch-1.pl b/challenge-168/cheok-yin-fung/perl/ch-1.pl
new file mode 100644
index 0000000000..faf90a9bb3
--- /dev/null
+++ b/challenge-168/cheok-yin-fung/perl/ch-1.pl
@@ -0,0 +1,29 @@
+#!/usr/bin/perl
+# The Weekly Challenge 168
+# Task 1 Perrin Prime 
+use v5.24.0;
+use warnings;
+use List::Util qw/none/;
+use Math::Prime::Util qw/is_prime/;
+
+my @perrin_primes = (2,3);
+my ($ppnm3,$ppnm2,$ppnm1, $ppn) = (3,0,2,3);
+
+while (scalar @perrin_primes < 13) {
+    if (is_prime($ppn) == 2) {
+        push @perrin_primes, $ppn if none {$_ == $ppn} @perrin_primes;
+        say $ppn;
+    }
+    $ppnm3 = $ppnm2;
+    $ppnm2 = $ppnm1;
+    $ppnm1 = $ppn;
+    $ppn = $ppnm2 + $ppnm3;
+}
+
+say join ", ", @perrin_primes;
+
+# time: 
+# real	0m0.025s
+# user	0m0.017s
+# sys	0m0.009s
+
diff --git a/challenge-168/cheok-yin-fung/perl/ch-2.pl b/challenge-168/cheok-yin-fung/perl/ch-2.pl
new file mode 100644
index 0000000000..00406d25ef
--- /dev/null
+++ b/challenge-168/cheok-yin-fung/perl/ch-2.pl
@@ -0,0 +1,72 @@
+#!/usr/bin/perl
+# The Weekly Challenge 168
+# Task 2 Home Prime 
+# Usage: ch-2.pl [integer > 1]
+use v5.24.0;
+use warnings;
+use Math::Prime::Util qw/is_prime next_prime/;
+use Math::BigInt;
+
+say hp($ARGV[0]) if defined($ARGV[0]) && $ARGV[0] != 1;
+
+
+
+sub hp {
+    my_hp($_[0],0);
+}
+
+
+
+sub my_hp {
+    my $num = $_[0];
+    my $recur_depth = $_[1];
+    die "Number involved too large.\n" 
+        if  
+            Math::BigInt->new("18446744073709551616") # 2**64
+                        ->ble( Math::BigInt->new($num) );
+    
+
+    if (is_prime($num) == 2) {
+        return $num;
+    }
+
+    die "Walk so far but still cannot get result. :(\n" if $recur_depth > 20;
+
+    my @factors = ();
+    my $p = 2;
+    while ($num != 1) {
+        if (!($num % $p)) {
+            push @factors, $p;
+            $num /= $p;
+        }
+        else {
+            $p = next_prime($p);
+        }
+        if ($p > sqrt $num) {
+            say "useful";
+            push @factors, $num;
+            last;
+        }
+    }
+    my $nxt = join "", @factors;
+    say "  $nxt";
+    return my_hp($nxt, ++$recur_depth);
+}
+
+use Test::More tests => 8;
+# test data from OEIS
+ok hp(10) == 773;
+ok hp(24) == 331_319;
+ok hp(32) == 241_271;
+ok hp(40) == 3314192745739;  
+ok hp(44) == 22815088913;  
+ok hp(45) == 3_411_949;
+
+# bigger cases;
+ok hp( 8) == 3331113965338635107;
+ok hp(20) == 3318308475676071413;
+
+# real	0m5.553s
+# user	0m5.535s
+# sys	0m0.016s
+
diff --git a/challenge-168/dave-jacoby/blog.txt b/challenge-168/dave-jacoby/blog.txt
new file mode 100644
index 0000000000..b28b04f643
--- /dev/null
+++ b/challenge-168/dave-jacoby/blog.txt
@@ -0,0 +1,3 @@
+
+
+
diff --git a/challenge-168/dave-jacoby/perl/ch-1.pl b/challenge-168/dave-jacoby/perl/ch-1.pl
new file mode 100644
index 0000000000..39a1510b86
--- /dev/null
+++ b/challenge-168/dave-jacoby/perl/ch-1.pl
@@ -0,0 +1,28 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+
+my @perrin = ( 3, 0, 2 );
+my %perrin_primes;
+$perrin_primes{2} = 1;
+$perrin_primes{3} = 1;
+
+while ( scalar keys %perrin_primes < 13 ) {
+    my $x = $perrin[-2] + $perrin[-3];
+    push @perrin, $x;
+    $perrin_primes{$x} = 1 if is_prime($x);
+}
+
+say join ' ', sort { $a <=> $b } keys %perrin_primes;
+exit;
+
+sub is_prime ($n) {
+    die "Bad number $n" unless length $n;
+    return 0 if $n == 0;
+    return 0 if $n == 1;
+    for ( 2 .. sqrt $n ) { return 0 unless $n % $_ }
+    return 1;
+}
+
diff --git a/challenge-168/dave-jacoby/perl/ch-2.pl b/challenge-168/dave-jacoby/perl/ch-2.pl
new file mode 100644
index 0000000000..1d101a36a4
--- /dev/null
+++ b/challenge-168/dave-jacoby/perl/ch-2.pl
@@ -0,0 +1,49 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use experimental qw{ say postderef signatures state };
+
+use Carp;
+use Try::Tiny;
+use Math::Prime::XS qw{ is_prime };
+
+$| = 1;
+
+my @n = @ARGV;
+push @n, 10 unless scalar @ARGV;
+
+for my $i (@n) {
+    try {
+        my $p = get_home_prime($i);
+        say join "\t", '-', $i, $p;
+    }
+    catch {
+        say $_;
+    };
+}
+
+sub get_home_prime($n) {
+    my $p = $n;
+    while ( !is_prime($p) ) {
+        my @factors = get_factors($p);
+        $p = join '', @factors;
+        print qq{$p };
+        # croak 'Too Big, Too Slow' if length $p > 10;
+    }
+    say '';
+    return $p;
+}
+
+sub get_factors( $n ) {
+    my @factors;
+    for my $i ( 2 .. $n ) {
+        next unless $n % $i == 0;
+        while ( $n % $i == 0 ) {
+            push @factors, $i;
+            $n = $n / $i;
+        }
+    }
+    return @factors;
+}
+
diff --git a/challenge-168/laurent-rosenfeld/blog.txt b/challenge-168/laurent-rosenfeld/blog.txt
new file mode 100644
index 0000000000..388761ba75
--- /dev/null
+++ b/challenge-168/laurent-rosenfeld/blog.txt
@@ -0,0 +1 @@
+http://blogs.perl.org/users/laurent_r/2022/06/perl-weekly-challenge-168-perrin-primes.html
diff --git a/challenge-168/laurent-rosenfeld/perl/ch-1.pl b/challenge-168/laurent-rosenfeld/perl/ch-1.pl
new file mode 100644
index 0000000000..906b341080
--- /dev/null
+++ b/challenge-168/laurent-rosenfeld/perl/ch-1.pl
@@ -0,0 +1,33 @@
+use strict;
+use warnings;
+use feature "say";
+
+my @perrin = (3, 0, 2);
+my @result = (2, 3);
+my %seen = map { $_ => 1 } @result;
+while (1) {
+    my $new_item = $perrin[-3] + $perrin[-2];
+    push @perrin, $new_item;
+    if (is_prime($new_item)) {
+        push @result, $new_item unless $seen{$new_item};
+        $seen{$new_item} = 1;
+        last if @result > 12;
+    }
+}
+say join " ", sort { $a <=> $b } @result;
+
+sub is_prime {
+   my $n = shift;
+   return 1 if $n == 2;
+   return 0 if $n % 2 == 0;
+   return 0 if $n == 1;
+
+   my $p = 3;
+   my $sqrt = sqrt $n;
+   while ($p <= $sqrt) {
+       # return 1 if $p >= $n;
+       return 0 if $n % $p == 0;
+       $p += 2;
+   }
+   return 1;
+}
diff --git a/challenge-168/laurent-rosenfeld/raku/ch-1.raku b/challenge-168/laurent-rosenfeld/raku/ch-1.raku
new file mode 100644
index 0000000000..f00ae2d3ef
--- /dev/null
+++ b/challenge-168/laurent-rosenfeld/raku/ch-1.raku
@@ -0,0 +1 @@
+say (unique grep {.is-prime}, (3, 0, 2, -> $a, $b, $c { $a + $b } ... ∞))[0..12].sort;
diff --git a/challenge-168/lubos-kolouch/perl/ch-2.pl b/challenge-168/lubos-kolouch/perl/ch-2.pl
new file mode 100644
index 0000000000..1390fba896
--- /dev/null
+++ b/challenge-168/lubos-kolouch/perl/ch-2.pl
@@ -0,0 +1,24 @@
+use strict;
+use warnings;
+use Math::Prime::Util qw/is_prime factor/;
+
+sub home_prime {
+    my $n = shift;
+
+    while ( !is_prime($n) ) {
+        my @factors = factor($n);
+        my $sum     = '';
+        foreach my $factor (@factors) {
+            $sum .= $factor;
+        }
+        $n = $sum;
+    }
+
+    return $n;
+}
+
+use Test::More;
+
+is( home_prime(2),  2 );
+is( home_prime(10), 773 );
+done_testing;
diff --git a/challenge-168/lubos-kolouch/python/ch-2.py b/challenge-168/lubos-kolouch/python/ch-2.py
new file mode 100644
index 0000000000..16094e836d
--- /dev/null
+++ b/challenge-168/lubos-kolouch/python/ch-2.py
@@ -0,0 +1,19 @@
+from sympy import factorint, isprime
+
+
+def home_prime(n):
+
+    while not isprime(n):
+        factors = factorint(n)
+
+        my_sum = ""
+        for (my_factor, repetition) in factors.items():
+            my_sum += str(my_factor) * repetition
+
+        n = int(my_sum)
+
+    return n
+
+
+assert home_prime(2) == 2
+assert home_prime(10) == 773
diff --git a/challenge-168/mattneleigh/perl/ch-1.pl b/challenge-168/mattneleigh/perl/ch-1.pl
new file mode 100755
index 0000000000..9ea3014572
--- /dev/null
+++ b/challenge-168/mattneleigh/perl/ch-1.pl
@@ -0,0 +1,99 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use English;
+
+################################################################################
+# Begin main execution
+################################################################################
+
+my @perrin = (3, 0, 2);
+my %perrin_primes = (
+    3 => 1,
+    2 => 1
+);
+my $num = 13;
+
+while(scalar(keys(%perrin_primes)) < $num){
+    next_perrin(\@perrin, 1);
+    $perrin_primes{$perrin[$#perrin]} = 1
+        if(is_prime($perrin[$#perrin]));
+}
+
+print("\n");
+printf(
+    "f(%d) = [%s]\n",
+    $num,
+    join(", ", sort({ $a <=> $b } keys(%perrin_primes)))
+);
+print("\n");
+
+exit(0);
+################################################################################
+# End main execution; subroutines follow
+################################################################################
+
+
+
+################################################################################
+# Calculate the next number in the Perrin sequence, adding it to an existing
+# list of Perrin numbers; see https://en.wikipedia.org/wiki/Perrin_number for
+# details about this type of number
+# Takes one or two arguments:
+# * A ref to a list of Perrin numbers; upon first call to this function, this
+#   list must be [ 3, 0, 2 ]
+# * An agument that, if defined, will cause the first member of the list to be
+#   removed after the new one is added, preventing the list from growing
+# Returns no meaningful value
+################################################################################
+sub next_perrin{
+    my $perrin = shift();
+
+    # Add the next number in the sequence
+    push(
+        @{$perrin},
+        $perrin->[$#$perrin - 2] + $perrin->[$#$perrin - 1]
+    );
+
+    # If specified, toss out the oldest number
+    shift(@{$perrin})
+        if(defined(shift()));
+
+}
+
+
+
+################################################################################
+# Determine whether a given integer N is prime
+# Takes one argument:
+# * The integer N
+# Returns on success:
+# * 1 if N is prime
+# * 0 if N is not prime
+# NOTE: If N is less than zero, it will always be considered nonprime
+################################################################################
+sub is_prime{
+    my $n = int(shift());
+
+    my $i;
+
+    # Take care of a few easy cases
+    return(1)
+        if(($n == 2) || ($n == 3));
+    return(0)
+        if(($n <= 1) || !($n % 2) || !($n % 3));
+
+    # See if certain factors divide evenly
+    for($i = 5; $i * $i <= $n; $i += 6){
+        if(!($n % $i) || !($n % ($i + 2))){
+            return(0);
+        }
+    }
+
+    return(1);
+
+}
+
+
+
diff --git a/challenge-168/mattneleigh/perl/ch-2.pl b/challenge-168/mattneleigh/perl/ch-2.pl
new file mode 100755
index 0000000000..73a5a0962f
--- /dev/null
+++ b/challenge-168/mattneleigh/perl/ch-2.pl
@@ -0,0 +1,141 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use English;
+
+################################################################################
+# Begin main execution
+################################################################################
+
+my $n = 10;
+
+# If you have some time on your hands...
+# $n = 8;
+
+print("\n");
+printf("HP(%d) = %d\n", $n, calculate_home_prime($n));
+print("\n");
+
+exit(0);
+################################################################################
+# End main execution; subroutines follow
+################################################################################
+
+
+
+################################################################################
+# Calculate the home prime of a given integer; see
+# https://en.wikipedia.org/wiki/Home_prime for details about this type of
+# number
+# Takes one argument:
+# * An integer N, which must be at least two (2)
+# Returns on success:
+# * The home prime of N
+# Returns on error:
+# * undef if N is less than two (2)
+# NOTE: For certain values of N, this calculation can take wholly unreasonable
+# amounts of time
+################################################################################
+sub calculate_home_prime{
+    my $n = int(shift());
+
+    return(undef)
+        if($n < 2);
+
+    # Loop until $n is prime
+    until(is_prime($n)){
+        my @factors;
+
+        # Get the prime factors of $n, and concatenate
+        # them into a new $n
+        prime_factorize_number($n, \@factors);
+        $n = join("", @factors);
+    }
+
+    return($n);
+
+}
+
+
+
+################################################################################
+# Find the prime factorization of a given integer
+# Takes two arguments:
+# * The integer N to examine and factor
+# * A ref to a list that will be populated with prime factors in ascending
+#   order; any previous contents will be deleted
+# Returns no meaningful value
+################################################################################
+sub prime_factorize_number{
+    use POSIX;
+
+    my $n = int(shift());
+    my $factors = shift();
+
+    # Clobber existing list contents if any
+    splice(@{$factors}, 0)
+        if(scalar(@{$factors}));
+
+    # Loop until $n is prime
+    until(is_prime($n)){
+        # $n is not prime; set an upper bound on
+        # our factor search
+        my $i;
+        my $max = ceil(sqrt($n));
+
+        # Loop until we find prime $i that
+        # divides evenly into $n
+        for($i=2; $i<=$max; $i++){
+            next unless(is_prime($i));
+            last unless($n % $i);
+        }
+
+        # Store the new prime factor $i and
+        # divide $n by it
+        push(@{$factors}, $i);
+        $n /= $i;
+
+    }
+
+    # Store $n, which by now is the last prime
+    # factor of the originally-supplied argument
+    push(@{$factors}, $n);
+
+}
+
+
+
+################################################################################
+# Determine whether a given integer N is prime
+# Takes one argument:
+# * The integer N
+# Returns on success:
+# * 1 if N is prime
+# * 0 if N is not prime
+# NOTE: If N is less than zero, it will always be considered nonprime
+################################################################################
+sub is_prime{
+    my $n = int(shift());
+
+    my $i;
+
+    # Take care of a few easy cases
+    return(1)
+        if(($n == 2) || ($n == 3));
+    return(0)
+        if(($n <= 1) || !($n % 2) || !($n % 3));
+
+    # See if certain factors divide evenly
+    for($i = 5; $i * $i <= $n; $i += 6){
+        if(!($n % $i) || !($n % ($i + 2))){
+            return(0);
+        }
+    }
+
+    return(1);
+
+}
+
+
+
diff --git a/challenge-168/polettix/blog.txt b/challenge-168/polettix/blog.txt
new file mode 100644
index 0000000000..f6337130ae
--- /dev/null
+++ b/challenge-168/polettix/blog.txt
@@ -0,0 +1 @@
+https://github.polettix.it/ETOOBUSY/2022/06/08/pwc168-perrin-prime/
diff --git a/challenge-168/polettix/blog1.txt b/challenge-168/polettix/blog1.txt
new file mode 100644
index 0000000000..ad226cc866
--- /dev/null
+++ b/challenge-168/polettix/blog1.txt
@@ -0,0 +1 @@
+https://github.polettix.it/ETOOBUSY/2022/06/09/pwc168-home-prime/
diff --git a/challenge-168/polettix/perl/ch-1.pl b/challenge-168/polettix/perl/ch-1.pl
new file mode 100644
index 0000000000..e4952fb0ed
--- /dev/null
+++ b/challenge-168/polettix/perl/ch-1.pl
@@ -0,0 +1,21 @@
+#!/usr/bin/env perl
+use v5.24;
+use warnings;
+use experimental 'signatures';
+no warnings 'experimental::signatures';
+
+use ntheory 'is_prime';
+
+my $n = shift // 13;
+say join ', ', perrin_primes($n);
+
+sub perrin_primes ($n) {
+   my @pps = (2, 3, 5);
+   my @state = (2, 5, 5);
+   while (@pps < $n) {
+      push @state, my $candidate = $state[0] + $state[1];
+      shift @state;
+      push @pps, $candidate if is_prime($candidate);
+   }
+   return @pps;
+}
diff --git a/challenge-168/polettix/perl/ch-2.pl b/challenge-168/polettix/perl/ch-2.pl
new file mode 100644
index 0000000000..24a1dd1255
--- /dev/null
+++ b/challenge-168/polettix/perl/ch-2.pl
@@ -0,0 +1,17 @@
+#!/usr/bin/env perl
+use v5.24;
+use warnings;
+use experimental 'signatures';
+no warnings 'experimental::signatures';
+
+use ntheory qw< factor >;
+
+my $n = shift // 10;
+say home_prime($n);
+
+sub home_prime {
+   my $next = join '', factor($_[0]);
+   return $next if $next eq $_[0];
+   $_[0] = $next;
+   goto &home_prime;
+}
diff --git a/challenge-168/polettix/perl/cpanfile b/challenge-168/polettix/perl/cpanfile
new file mode 100644
index 0000000000..94ac365d6f
--- /dev/null
+++ b/challenge-168/polettix/perl/cpanfile
@@ -0,0 +1 @@
+requires 'ntheory';
diff --git a/challenge-168/polettix/perl/cpanfile.snapshot b/challenge-168/polettix/perl/cpanfile.snapshot
new file mode 100644
index 0000000000..2fd600a3af
--- /dev/null
+++ b/challenge-168/polettix/perl/cpanfile.snapshot
@@ -0,0 +1,38 @@
+# carton snapshot format: version 1.0
+DISTRIBUTIONS
+  Math-Prime-Util-0.73
+    pathname: D/DA/DANAJ/Math-Prime-Util-0.73.tar.gz
+    provides:
+      Math::Prime::Util 0.73
+      Math::Prime::Util::ChaCha 0.73
+      Math::Prime::Util::Entropy 0.73
+      Math::Prime::Util::MemFree 0.73
+      Math::Prime::Util::PP 0.73
+      Math::Prime::Util::PrimeArray 0.73
+      Math::Prime::Util::PrimeIterator 0.73
+      ntheory 0.73
+    requirements:
+      Carp 0
+      Config 0
+      Exporter 5.57
+      ExtUtils::MakeMaker 0
+      Math::BigFloat 1.59
+      Math::BigInt 1.88
+      Math::Prime::Util::GMP 0.50
+      Tie::Array 0
+      XSLoader 0.01
+      base 0
+      constant 0
+      perl 5.006002
+  Math-Prime-Util-GMP-0.52
+    pathname: D/DA/DANAJ/Math-Prime-Util-GMP-0.52.tar.gz
+    provides:
+      Math::Prime::Util::GMP 0.52
+    requirements:
+      Carp 0
+      Exporter 5.57
+      ExtUtils::MakeMaker 0
+      Fcntl 0
+      XSLoader 0.01
+      base 0
+      perl 5.006002
diff --git a/challenge-168/polettix/raku/ch-1.raku b/challenge-168/polettix/raku/ch-1.raku
new file mode 100644
index 0000000000..28f3b1fb86
--- /dev/null
+++ b/challenge-168/polettix/raku/ch-1.raku
@@ -0,0 +1,28 @@
+#!/usr/bin/env raku
+use v6;
+
+class PerrinSequence {
+   has @!state = [3, 0, 2];
+   method get () {
+      @!state.push(@!state[0] + @!state[1]);
+      return @!state.shift;
+   }
+}
+
+multi sub MAIN (1) { put 2 }
+
+multi sub MAIN (2) { put '2, 3' }
+
+multi sub MAIN (3) { put '2, 3, 5' }
+
+multi sub MAIN (Int:D $n is copy where * > 3 = 13) {
+   my $ps = PerrinSequence.new;
+   $ps.get for 1..7;
+   my @n-primes = gather while $n > 3 {
+      my $candidate = $ps.get;
+      next unless $candidate.is-prime;
+      take $candidate;
+      --$n;
+   }
+   [2, 3, 5, |@n-primes].join(', ').put;
+}
diff --git a/challenge-168/polettix/raku/ch-2.raku b/challenge-168/polettix/raku/ch-2.raku
new file mode 100644
index 0000000000..5de2d6efd4
--- /dev/null
+++ b/challenge-168/polettix/raku/ch-2.raku
@@ -0,0 +1,31 @@
+#!/usr/bin/env raku
+use v6;
+sub MAIN (Int:D $n where * > 1 = 10) { put home-prime($n) }
+
+sub home-prime ($n is copy) {
+   loop {
+      my $m = factors($n).join('').Int;
+      return $n if $n == $m;
+      $n = $m;
+   }
+}
+
+sub factors (Int $remainder is copy) {
+   return 1 if $remainder <= 1;
+   state @primes = 2, 3, 5, -> $n is copy {
+      repeat { $n += 2 } until $n %% none @primes ... { $_ * $_ >= $n }
+      $n;
+   } ... *;
+   gather for @primes -> $factor {
+      if $factor * $factor > $remainder {
+         take $remainder if $remainder > 1;
+         last;
+      }
+
+      # How many times can we divide by this prime?
+      while $remainder %% $factor {
+         take $factor;
+         last if ($remainder div= $factor) === 1;
+      }
+   }
+}
diff --git a/challenge-168/steve-g-lynn/julia/ch-2.jl b/challenge-168/steve-g-lynn/julia/ch-2.jl
index 19d4c7d498..0828857250 100755
--- a/challenge-168/steve-g-lynn/julia/ch-2.jl
+++ b/challenge-168/steve-g-lynn/julia/ch-2.jl
@@ -1,15 +1,56 @@
 #! /usr/bin/julia
 
+#time (bash) output: with homeprime.([10,16,20,48,65,96])
+#real	0m41.340s
+#user	0m41.149s
+#sys	0m0.493s
+
+#-- without homeprime(96):
+#real	0m4.744s
+#user	0m4.745s
+#sys	0m0.467s
+
+#-- without .homeprime.([96,65])
+#real	0m1.072s
+#user	0m1.138s
+#sys	0m0.419s
+
+#-- without .homeprime.([96,65,48])
+#real	0m1.002s
+#user	0m1.095s
+#sys	0m0.384s
+
+
+
 using Primes
 
 function homeprime(n::Int64)
+	return homeprime(BigInt(n))
+end
+
+function homeprime(n::BigInt)
 	ncopy=n
 	while (!isprime(ncopy))
-		ncopy=parse(Int64,join(factor(Vector,ncopy)))
+		ncopy=parse(BigInt,join(factor(Vector,ncopy)))
 	end
 	return ncopy
 end
 
+println(homeprime(10))
+#773
+
 println(homeprime(16))
 #31636373
 
+println(homeprime(20))
+#3318308475676071413
+
+println(homeprime(48))
+#6161791591356884791277
+
+println(homeprime(65))
+#1381321118321175157763339900357651
+
+println(homeprime(96))
+#172929671097972226356946608292031596899264419
+
diff --git a/challenge-168/steve-g-lynn/perl/ch-2.pl b/challenge-168/steve-g-lynn/perl/ch-2.pl
index d1f6f0aced..0548ac1ebc 100755
--- a/challenge-168/steve-g-lynn/perl/ch-2.pl
+++ b/challenge-168/steve-g-lynn/perl/ch-2.pl
@@ -1,37 +1,35 @@
 #!/usr/bin/perl
 
-use Math::Prime::XS qw(is_prime sieve_primes);
+#time (bash) output:
+#real	0m0.026s
+#user	0m0.019s
+#sys	0m0.007s
 
+# but this fast time degrades sharply with larger problems
+#
+# real is 0m45.199s if home_prime(48) also printed
+# real is 5m5.662s if home_prime of 48 and 65 also printed
+# real is 8m50.059s if home_prime of 48, 65 and 96 also printed
+#
+# probably some slowdown in factor(.) for factors of very large primes 
+
+use Math::Prime::Util qw(is_prime factor);
+