[libmath-prime-util-perl] 48/181: New factor_exp function

[Partha P. Mukherjee]

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ppm-guest pushed a commit to annotated tag v0.36
in repository libmath-prime-util-perl.

commit 690a97ff9c7d38a33c386faaacb83c1bb2d48b66
Author: Dana Jacobsen <dana at acm.org>
Date:   Fri Dec 27 18:15:05 2013 -0800

    New factor_exp function
---
 factor.c | 31 ++++++++++++++++++++-----------
 factor.h |  1 +
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/factor.c b/factor.c
index 6da205a..4e0c337 100644
--- a/factor.c
+++ b/factor.c
@@ -132,6 +132,25 @@ int factor(UV n, UV *factors)
   return nfactors;
 }
 
+int factor_exp(UV n, UV *factors, UV* exponents)
+{
+  int i, j, nfactors = factor(n, factors);
+
+  if (n == 1) return 0;
+  exponents[0] = 1;
+  for (i = 1, j = 1; i < nfactors; i++) {
+    if (factors[i] != factors[i-1]) {
+      exponents[j] = 1;
+      factors[j++] = factors[i];
+    } else {
+      exponents[j-1]++;
+    }
+  }
+  return j;
+}
+
+
+
 static const unsigned short primes_small[] =
   {0,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
    101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,
@@ -330,17 +349,7 @@ UV* _divisor_list(UV n, UV *num_divisors)
     return divs;
   }
   /* Factor and convert to factor/exponent pair */
-  nfactors = factor(n, factors);
-  exponents[0] = 1;
-  for (i = 1, j = 1; i < nfactors; i++) {
-    if (factors[i] != factors[i-1]) {
-      exponents[j] = 1;
-      factors[j++] = factors[i];
-    } else {
-      exponents[j-1]++;
-    }
-  }
-  nfactors = j;
+  nfactors = factor_exp(n, factors, exponents);
   /* Calculate number of divisors, allocate space, fill with divisors */
   ndivisors = exponents[0] + 1;
   for (i = 1; i < nfactors; i++)
diff --git a/factor.h b/factor.h
index 862fb65..41cf3c5 100644
--- a/factor.h
+++ b/factor.h
@@ -6,6 +6,7 @@
 #define MPU_MAX_FACTORS 64
 
 extern int factor(UV n, UV *factors);
+extern int factor_exp(UV n, UV *factors, UV* exponents);
 
 extern int trial_factor(UV n, UV *factors, UV maxtrial);
 

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