[Guile-commits] 18/85: Implement round-divide with new integer lib

[Andy Wingo]

wingo pushed a commit to branch main
in repository guile.

commit 025c7c80451c9394cff1e15ce278d34a01a98022
Author: Andy Wingo <wingo@pobox.com>
AuthorDate: Mon Dec 13 12:12:54 2021 +0100

    Implement round-divide with new integer lib
    
    * libguile/integers.c (scm_integer_round_divide_ii)
    (scm_integer_round_divide_iz, scm_integer_round_divide_zi)
    (scm_integer_round_divide_zz): New internal functions.
    (integer_round_divide_zz): New helper.
    * libguile/integers.h: Declare internal functions.
    * libguile/numbers.c (scm_round_divide): Use the new functions.
    (scm_i_bigint_round_divide): Remove unused helper.
---
 libguile/integers.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++
 libguile/integers.h |   9 ++++
 libguile/numbers.c  | 131 ++++------------------------------------------------
 3 files changed, 140 insertions(+), 123 deletions(-)

diff --git a/libguile/integers.c b/libguile/integers.c
index 715d2ed6f..45f769f56 100644
--- a/libguile/integers.c
+++ b/libguile/integers.c
@@ -1619,3 +1619,126 @@ scm_integer_round_remainder_zz (SCM x, SCM y)
 {
   return integer_round_remainder_zz (scm_bignum (x), scm_bignum (y));
 }
+
+static void
+integer_round_divide_zz (struct scm_bignum *x, struct scm_bignum *y,
+                         SCM *qp, SCM *rp)
+{
+  mpz_t q, r, r2, zx, zy;
+  int cmp, needs_adjustment;
+
+  /* Note that x might be small enough to fit into a fixnum, so we must
+     not let it escape into the wild */
+  mpz_init (q);
+  mpz_init (r);
+  mpz_init (r2);
+  alias_bignum_to_mpz (x, zx);
+  alias_bignum_to_mpz (y, zy);
+
+  mpz_fdiv_qr (q, r, zx, zy);
+  scm_remember_upto_here_1 (x);
+  mpz_mul_2exp (r2, r, 1);  /* r2 = 2*r */
+
+  cmp = mpz_cmpabs (r2, zy);
+  if (mpz_odd_p (q))
+    needs_adjustment = (cmp >= 0);
+  else
+    needs_adjustment = (cmp > 0);
+
+  if (needs_adjustment)
+    {
+      mpz_add_ui (q, q, 1);
+      mpz_sub (r, r, zy);
+    }
+
+  scm_remember_upto_here_1 (y);
+  mpz_clear (r2);
+  *qp = take_mpz (q);
+  *rp = take_mpz (r);
+}
+
+void
+scm_integer_round_divide_ii (scm_t_inum x, scm_t_inum y, SCM *qp, SCM *rp)
+{
+  if (y == 0)
+    scm_num_overflow ("round-divide");
+
+  scm_t_inum q = x / y;
+  scm_t_inum r = x % y;
+  scm_t_inum ay = y;
+  scm_t_inum r2 = 2 * r;
+
+  if (y < 0)
+    {
+      ay = -ay;
+      r2 = -r2;
+    }
+
+  if (q & 1L)
+    {
+      if (r2 >= ay)
+        { q++; r -= y; }
+      else if (r2 <= -ay)
+        { q--; r += y; }
+    }
+  else
+    {
+      if (r2 > ay)
+        { q++; r -= y; }
+      else if (r2 < -ay)
+        { q--; r += y; }
+    }
+  *qp = long_to_scm (q);
+  *rp = SCM_I_MAKINUM (r);
+}
+
+void
+scm_integer_round_divide_iz (scm_t_inum x, SCM y, SCM *qp, SCM *rp)
+{
+  integer_round_divide_zz (long_to_bignum (x), scm_bignum (y), qp, rp);
+}
+
+void
+scm_integer_round_divide_zi (SCM x, scm_t_inum y, SCM *qp, SCM *rp)
+{
+  if (y == 0)
+    scm_num_overflow ("round-divide");
+
+  mpz_t q, zx;
+  mpz_init (q);
+  alias_bignum_to_mpz (scm_bignum (x), zx);
+  scm_t_inum r;
+  int needs_adjustment;
+
+  if (y > 0)
+    {
+      r = mpz_fdiv_q_ui (q, zx, y);
+      if (mpz_odd_p (q))
+        needs_adjustment = (2*r >= y);
+      else
+        needs_adjustment = (2*r > y);
+    }
+  else
+    {
+      r = - mpz_cdiv_q_ui (q, zx, -y);
+      mpz_neg (q, q);
+      if (mpz_odd_p (q))
+        needs_adjustment = (2*r <= y);
+      else
+        needs_adjustment = (2*r < y);
+    }
+  scm_remember_upto_here_1 (x);
+  if (needs_adjustment)
+    {
+      mpz_add_ui (q, q, 1);
+      r -= y;
+    }
+  *qp = take_mpz (q);
+  *rp = SCM_I_MAKINUM (r);
+}
+
+void
+scm_integer_round_divide_zz (SCM x, SCM y, SCM *qp, SCM *rp)
+{
+  integer_round_divide_zz (scm_bignum (x), scm_bignum (y), qp, rp);
+}
diff --git a/libguile/integers.h b/libguile/integers.h
index 6628b444d..e1193c231 100644
--- a/libguile/integers.h
+++ b/libguile/integers.h
@@ -115,6 +115,15 @@ SCM_INTERNAL SCM scm_integer_round_remainder_iz 
(scm_t_inum x, SCM y);
 SCM_INTERNAL SCM scm_integer_round_remainder_zi (SCM x, scm_t_inum y);
 SCM_INTERNAL SCM scm_integer_round_remainder_zz (SCM x, SCM y);
 
+SCM_INTERNAL void scm_integer_round_divide_ii (scm_t_inum x, scm_t_inum y,
+                                               SCM *qp, SCM *rp);
+SCM_INTERNAL void scm_integer_round_divide_iz (scm_t_inum x, SCM y,
+                                               SCM *qp, SCM *rp);
+SCM_INTERNAL void scm_integer_round_divide_zi (SCM x, scm_t_inum y,
+                                               SCM *qp, SCM *rp);
+SCM_INTERNAL void scm_integer_round_divide_zz (SCM x, SCM y,
+                                               SCM *qp, SCM *rp);
+
 
 
 #endif  /* SCM_INTEGERS_H */
diff --git a/libguile/numbers.c b/libguile/numbers.c
index 55dfd58cf..32dad4d01 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -2644,7 +2644,6 @@ scm_i_exact_rational_round_remainder (SCM x, SCM y)
 
 
 static void scm_i_inexact_round_divide (double x, double y, SCM *qp, SCM *rp);
-static void scm_i_bigint_round_divide (SCM x, SCM y, SCM *qp, SCM *rp);
 static void scm_i_exact_rational_round_divide (SCM x, SCM y, SCM *qp, SCM *rp);
 
 SCM_PRIMITIVE_GENERIC (scm_i_round_divide, "round/", 2, 0, 0,
@@ -2679,54 +2678,14 @@ SCM_PRIMITIVE_GENERIC (scm_i_round_divide, "round/", 2, 
0, 0,
 void
 scm_round_divide (SCM x, SCM y, SCM *qp, SCM *rp)
 {
-  if (SCM_LIKELY (SCM_I_INUMP (x)))
+  if (SCM_I_INUMP (x))
     {
-      scm_t_inum xx = SCM_I_INUM (x);
-      if (SCM_LIKELY (SCM_I_INUMP (y)))
-       {
-         scm_t_inum yy = SCM_I_INUM (y);
-         if (SCM_UNLIKELY (yy == 0))
-           scm_num_overflow (s_scm_round_divide);
-         else
-           {
-             scm_t_inum qq = xx / yy;
-             scm_t_inum rr = xx % yy;
-             scm_t_inum ay = yy;
-             scm_t_inum r2 = 2 * rr;
-
-             if (SCM_LIKELY (yy < 0))
-               {
-                 ay = -ay;
-                 r2 = -r2;
-               }
-
-             if (qq & 1L)
-               {
-                 if (r2 >= ay)
-                   { qq++; rr -= yy; }
-                 else if (r2 <= -ay)
-                   { qq--; rr += yy; }
-               }
-             else
-               {
-                 if (r2 > ay)
-                   { qq++; rr -= yy; }
-                 else if (r2 < -ay)
-                   { qq--; rr += yy; }
-               }
-             if (SCM_LIKELY (SCM_FIXABLE (qq)))
-               *qp = SCM_I_MAKINUM (qq);
-             else
-               *qp = scm_i_inum2big (qq);
-             *rp = SCM_I_MAKINUM (rr);
-           }
-       }
+      if (SCM_I_INUMP (y))
+        scm_integer_round_divide_ii (SCM_I_INUM (x), SCM_I_INUM (y), qp, rp);
       else if (SCM_BIGP (y))
-        /* Pass a denormalized bignum version of x (even though it
-           can fit in a fixnum) to scm_i_bigint_round_divide */
-        scm_i_bigint_round_divide (scm_i_long2big (SCM_I_INUM (x)), y, qp, rp);
+        scm_integer_round_divide_iz (SCM_I_INUM (x), y, qp, rp);
       else if (SCM_REALP (y))
-       scm_i_inexact_round_divide (xx, SCM_REAL_VALUE (y), qp, rp);
+       scm_i_inexact_round_divide (SCM_I_INUM (x), SCM_REAL_VALUE (y), qp, rp);
       else if (SCM_FRACTIONP (y))
        scm_i_exact_rational_round_divide (x, y, qp, rp);
       else
@@ -2735,48 +2694,10 @@ scm_round_divide (SCM x, SCM y, SCM *qp, SCM *rp)
     }
   else if (SCM_BIGP (x))
     {
-      if (SCM_LIKELY (SCM_I_INUMP (y)))
-       {
-         scm_t_inum yy = SCM_I_INUM (y);
-         if (SCM_UNLIKELY (yy == 0))
-           scm_num_overflow (s_scm_round_divide);
-         else
-           {
-             SCM q = scm_i_mkbig ();
-             scm_t_inum rr;
-             int needs_adjustment;
-
-             if (yy > 0)
-               {
-                 rr = mpz_fdiv_q_ui (SCM_I_BIG_MPZ (q),
-                                     SCM_I_BIG_MPZ (x), yy);
-                 if (mpz_odd_p (SCM_I_BIG_MPZ (q)))
-                   needs_adjustment = (2*rr >= yy);
-                 else
-                   needs_adjustment = (2*rr > yy);
-               }
-             else
-               {
-                 rr = - mpz_cdiv_q_ui (SCM_I_BIG_MPZ (q),
-                                       SCM_I_BIG_MPZ (x), -yy);
-                 mpz_neg (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (q));
-                 if (mpz_odd_p (SCM_I_BIG_MPZ (q)))
-                   needs_adjustment = (2*rr <= yy);
-                 else
-                   needs_adjustment = (2*rr < yy);
-               }
-             scm_remember_upto_here_1 (x);
-             if (needs_adjustment)
-               {
-                 mpz_add_ui (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (q), 1);
-                 rr -= yy;
-               }
-             *qp = scm_i_normbig (q);
-             *rp = SCM_I_MAKINUM (rr);
-           }
-       }
+      if (SCM_I_INUMP (y))
+        scm_integer_round_divide_zi (x, SCM_I_INUM (y), qp, rp);
       else if (SCM_BIGP (y))
-       scm_i_bigint_round_divide (x, y, qp, rp);
+        scm_integer_round_divide_zz (x, y, qp, rp);
       else if (SCM_REALP (y))
        scm_i_inexact_round_divide (scm_i_big2dbl (x), SCM_REAL_VALUE (y),
                                     qp, rp);
@@ -2826,42 +2747,6 @@ scm_i_inexact_round_divide (double x, double y, SCM *qp, 
SCM *rp)
     }
 }
 
-/* Assumes that both x and y are bigints, though
-   x might be able to fit into a fixnum. */
-static void
-scm_i_bigint_round_divide (SCM x, SCM y, SCM *qp, SCM *rp)
-{
-  SCM q, r, r2;
-  int cmp, needs_adjustment;
-
-  /* Note that x might be small enough to fit into a
-     fixnum, so we must not let it escape into the wild */
-  q = scm_i_mkbig ();
-  r = scm_i_mkbig ();
-  r2 = scm_i_mkbig ();
-
-  mpz_fdiv_qr (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (r),
-              SCM_I_BIG_MPZ (x), SCM_I_BIG_MPZ (y));
-  scm_remember_upto_here_1 (x);
-  mpz_mul_2exp (SCM_I_BIG_MPZ (r2), SCM_I_BIG_MPZ (r), 1);  /* r2 = 2*r */
-
-  cmp = mpz_cmpabs (SCM_I_BIG_MPZ (r2), SCM_I_BIG_MPZ (y));
-  if (mpz_odd_p (SCM_I_BIG_MPZ (q)))
-    needs_adjustment = (cmp >= 0);
-  else
-    needs_adjustment = (cmp > 0);
-
-  if (needs_adjustment)
-    {
-      mpz_add_ui (SCM_I_BIG_MPZ (q), SCM_I_BIG_MPZ (q), 1);
-      mpz_sub (SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (r), SCM_I_BIG_MPZ (y));
-    }
-
-  scm_remember_upto_here_2 (r2, y);
-  *qp = scm_i_normbig (q);
-  *rp = scm_i_normbig (r);
-}
-
 static void
 scm_i_exact_rational_round_divide (SCM x, SCM y, SCM *qp, SCM *rp)
 {