[libmath-prime-util-perl] 10/25: Put icbrt in util.h

[Partha P. Mukherjee]

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ppm-guest pushed a commit to annotated tag v0.35
in repository libmath-prime-util-perl.

commit 6b63be20ca4ca868f83a352887a0ace21c8f2daf
Author: Dana Jacobsen <dana at acm.org>
Date:   Thu Dec 5 10:55:43 2013 -0800

    Put icbrt in util.h
---
 lehmer.c | 57 ++++++++++++++++++++-------------------------------------
 lmo.c    | 16 +---------------
 util.h   | 22 ++++++++++++++++++++++
 3 files changed, 43 insertions(+), 52 deletions(-)

diff --git a/lehmer.c b/lehmer.c
index 368d194..4e6488f 100644
--- a/lehmer.c
+++ b/lehmer.c
@@ -130,8 +130,7 @@ typedef   signed long IV;
 #define prime_precalc(n)          /* */
 #define BITS_PER_WORD             ((ULONG_MAX <= 4294967295UL) ? 32 : 64)
 
-static UV isqrt(UV n)
-{
+static UV isqrt(UV n) {
   UV root;
   if (sizeof(UV) == 8 && n >= 18446744065119617025UL)  return 4294967295UL;
   if (sizeof(UV) == 4 && n >= 4294836225UL)            return 65535UL;
@@ -140,6 +139,24 @@ static UV isqrt(UV n)
   while ((root+1)*(root+1) <= n)  root++;
   return root;
 }
+static UV icbrt(UV n) {
+  UV b, root = 0;
+  int s;
+  if (sizeof(UV) == 8) {
+    s = 63;  if (n >= 18446724184312856125UL)  return 2642245UL;
+  } else {
+    s = 30;  if (n >= 4291015625UL)            return 1625UL;
+  }
+  for ( ; s >= 0; s -= 3) {
+    root += root;
+    b = 3*root*(root+1)+1;
+    if ((n >> s) >= b) {
+      n -= b << s;
+      root++;
+    }
+  }
+  return root;
+}
 
 /* Callback used for creating an array of primes. */
 static uint32_t* sieve_array = 0;
@@ -198,6 +215,7 @@ static uint32_t* generate_small_primes(UV n)
 /* We will use pre-sieving to speed up counting for small ranges */
 #define SIEVE_MULT   1
 
+#define FUNC_icbrt 1
 #include "lehmer.h"
 #include "util.h"
 #include "cache.h"
@@ -233,42 +251,7 @@ static uint32_t* generate_small_primes(UV n)
   if (verbose > 1) printf("generated %lu small primes, from 2 to %lu\n", i, (unsigned long)primes[i]);
   return primes;
 }
-
-#endif
-
-static UV icbrt(UV n)
-{
-  UV root = 0;
-  /* int s = BITS_PER_WORD - (BITS_PER_WORD % 3); */
-#if BITS_PER_WORD == 32
-  int s = 30;
-  if (n >= UVCONST(4291015625)) return UVCONST(1625);
-#else
-  int s = 63;
-  if (n >= UVCONST(18446724184312856125)) return UVCONST(2642245);
-#endif
-#if 0
-  /* The integer cube root code is about 30% faster for me */
-  root = (UV) pow(n, 1.0/3.0);
-  if (root*root*root > n) {
-    root--;
-    while (root*root*root > n)  root--;
-  } else {
-    while ((root+1)*(root+1)*(root+1) <= n)  root++;
-  }
-#else
-  for ( ; s >= 0; s -= 3) {
-    UV b;
-    root += root;
-    b = 3*root*(root+1)+1;
-    if ((n >> s) >= b) {
-      n -= b << s;
-      root++;
-    }
-  }
 #endif
-  return root;
-}
 
 
 /* Given an array of primes[1..lastprime], return Pi(n) where n <= lastprime.
diff --git a/lmo.c b/lmo.c
index eb37c8d..7fcf321 100644
--- a/lmo.c
+++ b/lmo.c
@@ -56,6 +56,7 @@
 /* Phi sieve multiplier, adjust for best performance */
 #define PHI_SIEVE_MULT 13
 
+#define FUNC_icbrt 1
 #include "lmo.h"
 #include "util.h"
 #include "cache.h"
@@ -65,21 +66,6 @@ typedef unsigned char  uint8;
 typedef unsigned short uint16;
 typedef uint32_t       uint32;
 
-static UV icbrt(UV n) {
-  UV b, root = 0;
-  int s = 63;
-  if (n >= UVCONST(18446724184312856125)) return UVCONST(2642245);
-  for (; s >= 0; s -= 3) {
-    root += root;
-    b = 3*root*(root+1)+1;
-    if ((n >> s) >= b) {
-      n -= b << s;
-      root++;
-    }
-  }
-  return root;
-}
-
 static const unsigned char byte_ones[256] =
   {0,1,1,2,1,2,2,3,1,2,2,3,2,3,3,4,1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,
    1,2,2,3,2,3,3,4,2,3,3,4,3,4,4,5,2,3,3,4,3,4,4,5,3,4,4,5,4,5,5,6,
diff --git a/util.h b/util.h
index efc4107..15fd457 100644
--- a/util.h
+++ b/util.h
@@ -47,6 +47,28 @@ static UV isqrt(UV n) {
   return root;
 }
 
+#ifdef FUNC_icbrt
+static UV icbrt(UV n) {
+  UV b, root = 0;
+#if BITS_PER_WORD == 32
+  int s = 30;
+  if (n >= UVCONST(4291015625)) return UVCONST(1625);
+#else
+  int s = 63;
+  if (n >= UVCONST(18446724184312856125)) return UVCONST(2642245);
+#endif
+  for ( ; s >= 0; s -= 3) {
+    root += root;
+    b = 3*root*(root+1)+1;
+    if ((n >> s) >= b) {
+      n -= b << s;
+      root++;
+    }
+  }
+  return root;
+}
+#endif
+
 #ifdef FUNC_gcd_ui
 static UV gcd_ui(UV x, UV y) {
   UV t;

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