~ chicken-core (chicken-5) bdda1a0dcf1195e0e78e4b2e62678e4f44cd55fa

commit bdda1a0dcf1195e0e78e4b2e62678e4f44cd55fa
Author:     Peter Bex <peter@more-magic.net>
AuthorDate: Thu Jan 28 22:35:53 2016 +0100
Commit:     Peter Bex <peter@more-magic.net>
CommitDate: Thu Jan 28 22:39:26 2016 +0100

    Port another B/Z performance fix from numbers egg.
    
    This is actually the *proper* fix for the pathological case that
    revision b0711c4ca7f8e92dd18807a1c553e6ce649f1380 tried to fix: Because
    X is divided into DIV_LIMIT (BZ_DIFF_THRESHOLD) sized pieces, this only
    makes sense if Y is bigger than those pieces.
    
    Finally, the revision in which I tried to fix it also changed the name
    of the threshold parameter, but it didn't fix the #ifdef guard around
    it, which means it wasn't overrideable by the user like it should be.
    This changes back the name to the original, thereby fixing that problem
    as well.

diff --git a/chicken.h b/chicken.h
index 854bd952..232ea778 100644
--- a/chicken.h
+++ b/chicken.h
@@ -422,7 +422,7 @@ static inline int isinf_ld (long double x)
 /* This defines when to switch from schoolbook to Burnikel-Ziegler
  * division.  It creates even more garbage than Karatsuba :(
  */
-# define C_BURNIKEL_ZIEGLER_DIFF_THRESHOLD 300
+# define C_BURNIKEL_ZIEGLER_THRESHOLD 300
 #endif
 #ifndef C_RECURSIVE_TO_STRING_THRESHOLD
 /* This threshold is in terms of the expected string length. */
diff --git a/runtime.c b/runtime.c
index bbd24524..024af686 100644
--- a/runtime.c
+++ b/runtime.c
@@ -8882,7 +8882,8 @@ bignum_divrem(C_word **ptr, C_word x, C_word y, C_word *q, C_word *r)
   default:
     res = C_SCHEME_FALSE;
     size = C_bignum_size(x) - C_bignum_size(y);
-    if (size > C_BURNIKEL_ZIEGLER_DIFF_THRESHOLD) {
+    if (C_bignum_size(y) > C_BURNIKEL_ZIEGLER_THRESHOLD &&
+        size > C_BURNIKEL_ZIEGLER_THRESHOLD) {
       res = bignum_divide_burnikel_ziegler(ptr, x, y, q, r);
     }
 
@@ -8930,7 +8931,7 @@ bignum_divide_burnikel_ziegler(C_word **ptr, C_word x, C_word y, C_word *q, C_wo
    * below the threshold, so we can always split N in half.
    */
   s = C_bignum_size(y);
-  m = 1 << C_ilen(s / C_BURNIKEL_ZIEGLER_DIFF_THRESHOLD);
+  m = 1 << C_ilen(s / C_BURNIKEL_ZIEGLER_THRESHOLD);
   j = (s+m-1) / m;              /* j = s/m, rounded up */
   n = j * m;
 
@@ -9097,16 +9098,12 @@ burnikel_ziegler_2n_div_1n(C_word **ptr, C_word a, C_word b, C_word b1, C_word b
 {
   C_word kab[2][C_SIZEOF_FIX_BIGNUM*7], *ka, a12, a3, a4,
          q1 = C_fix(0), r1, q2 = C_fix(0), r2, *qp;
-  int stack_full = 0, size_a, size_b;
+  int stack_full = 0;
 
   C_stack_check1(stack_full = 1);
 
-  size_a = (a & C_FIXNUM_BIT) ? 1 : C_bignum_size(a);
-  size_b = (b & C_FIXNUM_BIT) ? 1 : C_bignum_size(b);
-  
   n = C_unfix(n);
-  if (stack_full || (n & 1) ||
-      ((size_a - size_b) < C_BURNIKEL_ZIEGLER_DIFF_THRESHOLD)) {
+  if (stack_full || (n & 1) || (n < C_BURNIKEL_ZIEGLER_THRESHOLD)) {
     integer_divrem(ptr, a, b, q, r);
   } else {
     ka = kab[0];