[libmath-prime-util-perl] 07/14: Tweak factoring and factor tests based on coverage analysis

[Partha P. Mukherjee]

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ppm-guest pushed a commit to annotated tag v0.25
in repository libmath-prime-util-perl.

commit c72237b008b6580aa5f662686184a693c732a9b1
Author: Dana Jacobsen <dana at acm.org>
Date:   Wed Mar 13 14:23:43 2013 -0700

    Tweak factoring and factor tests based on coverage analysis
---
 Changes          |  4 ++--
 TODO             |  3 ---
 factor.c         | 18 ++++++++----------
 t/50-factoring.t |  3 ++-
 4 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/Changes b/Changes
index 390d496..0102f37 100644
--- a/Changes
+++ b/Changes
@@ -2,8 +2,8 @@ Revision history for Perl extension Math::Prime::Util.
 
 0.25 xx March 2013
 
-    - Speed up p-1 stage 2 factoring.  This makes factor() about 20% faster
-      for 19 digit semiprimes.
+    - Speed up p-1 stage 2 factoring.  Combined with some minor changes to the
+      general factoring combination, ~20% faster for 19 digit semiprimes.
 
     - New internal macro to loop over primary sieve starting at 2.  Simplifies
       code in quite a few places.
diff --git a/TODO b/TODO
index a75cc17..b0be486 100644
--- a/TODO
+++ b/TODO
@@ -19,9 +19,6 @@
 
 - finish test suite for bignum.  Work on making it faster.
 
-- After the factoring changes, we need to use Devel::Cover again to ferret
-  out numbers that pass the early tests.
-
 - Test all routines for numbers on word-size boundary, or ranges that cross.
 
 - Test all functions return either native or bigints.  Functions that return
diff --git a/factor.c b/factor.c
index 26622cf..44f36bd 100644
--- a/factor.c
+++ b/factor.c
@@ -49,34 +49,31 @@ int factor(UV n, UV *factors)
       UV const br_rounds = ((n>>29) < 100000) ?  1500 :  1500;
       UV const sq_rounds = 80000; /* 20k 91%, 40k 98%, 80k 99.9%, 120k 99.99% */
 
-      /* About 94% of random inputs are factored with this pbrent call */
+      /* 99.7% of 32-bit, 94% of 64-bit random inputs factored here */
       if (!split_success) {
         split_success = pbrent_factor(n, tofac_stack+ntofac, br_rounds, 3)-1;
         if (verbose) { if (split_success) printf("pbrent 1:  %"UVuf" %"UVuf"\n", tofac_stack[ntofac], tofac_stack[ntofac+1]); else printf("pbrent 0\n"); }
       }
-      /* SQUFOF with these parameters gets 95% of what's left. */
+      /* SQUFOF with these parameters gets 99.9% of everything left */
       if (!split_success && n < (UV_MAX>>3)) {
         split_success = racing_squfof_factor(n,tofac_stack+ntofac, sq_rounds)-1;
         if (verbose) printf("rsqufof %d\n", split_success);
       }
-      /* Perhaps prho using different parameters will find it */
-      if (!split_success) {
-        split_success = pbrent_factor(n, tofac_stack+ntofac, 800, 5)-1;
-        if (verbose) printf("pbrent5 %d\n", split_success);
-      }
+      /* At this point we should only have 16+ digit semiprimes. */
       /* This p-1 gets about 2/3 of what makes it through the above */
       if (!split_success) {
         split_success = pminus1_factor(n, tofac_stack+ntofac, 5000, 80000)-1;
         if (verbose) printf("pminus1 %d\n", split_success);
       }
-      /* Some rounds of HOLF, good for close to perfect squares */
+      /* Some rounds of HOLF, good for close to perfect squares which are
+       * the worst case for the next step */
       if (!split_success) {
         split_success = holf_factor(n, tofac_stack+ntofac, 2000)-1;
         if (verbose) printf("holf %d\n", split_success);
       }
-      /* Less than 0.1% of random inputs make it here */
+      /* The catch-all.  Should factor anything. */
       if (!split_success) {
-        split_success = pbrent_factor(n, tofac_stack+ntofac, 256*1024, 7)-1;
+        split_success = prho_factor(n, tofac_stack+ntofac, 256*1024)-1;
         if (verbose) printf("long prho %d\n", split_success);
       }
 
@@ -277,6 +274,7 @@ static int is_perfect_square(UV n, UV* sqrtn)
   if ((m*0xabf1a3a7) & (m*0x2612bf93) & 0x45854000) return 0;
   /* 99.92% of non-squares are rejected now */
 #else
+  /* It may be faster to skip these */
   m = n % 63;
   if ((m*0x3d491df7) & (m*0xc824a9f9) & 0x10f14008) return 0;
 #endif
diff --git a/t/50-factoring.t b/t/50-factoring.t
index 35cf133..2d367a7 100644
--- a/t/50-factoring.t
+++ b/t/50-factoring.t
@@ -32,7 +32,7 @@ my @testn = qw/0 1 2 3 4 5 6 7 8 16 57 64 377 9592 30107 78498 664579 5761455
                808 2727 12625 34643 134431 221897 496213 692759 1228867
                2231139 2463289 3008891 5115953 6961021 8030207 10486123
                10893343 12327779 701737021
-               549900
+               549900 10000142
               /;
 
 my @testn64 = qw/37607912018 346065536839 600851475143
@@ -42,6 +42,7 @@ my @testn64 = qw/37607912018 346065536839 600851475143
                  9007199254740991 9007199254740992 9007199254740993
                  6469693230 200560490130 7420738134810 304250263527210
                  13082761331670030 614889782588491410
+                 440091295252541 5333042142001571
                 /;
 
 push @testn, @testn64 if $use64;

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