e$B$J$+$@$G$9!#e(B
e$B$A$g$C$HIbF0>.?tE@4X78e(B(e$B@53N$K$O4]$a4X78e(B)e$B$r8+D>$7$F$$$?$H$3$m!"e(B
2007-07-28 e$B$NLdBj$,%j%F%i%k0J30$G$OD>$Ce(B
e$B$F$$$J$$$3$H$K5$$E$-$^$7$?!#e(B
e$B0J2<$N%Q%C%A$G$O!"?te(B%e$B$+$ie(B10%e$B6/DxEYCY$/$J$k$h$&$G$9!#e(B
x=253+1
a = []
a.concat (0…33).map{|i|[(x << i) + 1, (x+1) << i]}
x=223+1
a.concat (7…33).map{|i|[(x << i) + 1, (x << i) + 1]}
a.each {|i,j| p i unless i.to_f==j}
t0 = Process.times
100000.times{a.each{|i,j| i.to_f}}
printf “%10.6f\n”, Process.times.utime-t0.utime
Index: bignum.c
— bignum.c (revision 15877)
+++ bignum.c (working copy)
@@ -1134,13 +1134,62 @@ rb_dbl2big(double d)
}
+static int
+nlz(BDIGIT x)
+{
- BDIGIT y;
- int n = BITSPERDIG;
+#if BITSPERDIG > 64 - y = x >> 64; if (y) {n -= 64; x = y;}
+#endif
+#if BITSPERDIG > 32 - y = x >> 32; if (y) {n -= 32; x = y;}
+#endif
+#if BITSPERDIG > 16 - y = x >> 16; if (y) {n -= 16; x = y;}
+#endif - y = x >> 8; if (y) {n -= 8; x = y;}
- y = x >> 4; if (y) {n -= 4; x = y;}
- y = x >> 2; if (y) {n -= 2; x = y;}
- y = x >> 1; if (y) {return n - 2;}
- return n - x;
+}
static double
big2dbl(VALUE x)
{
double d = 0.0;
- long i = RBIGNUM_LEN(x);
- BDIGIT *ds = BDIGITS(x);
- long i = RBIGNUM_LEN(x), lo = 0, bits;
- BDIGIT *ds = BDIGITS(x), dl;
- while (i–) {
- d = ds[i] + BIGRAD*d;
- if (i) {
- bits = i * BITSPERDIG - nlz(ds[i-1]);
- if (bits > DBL_MANT_DIG+DBL_MAX_EXP) {
-
d = HUGE_VAL; - }
- else {
-
if (bits > DBL_MANT_DIG+1) - lo = (bits -= DBL_MANT_DIG+1) / BITSPERDIG;
-
else - bits = 0;
-
while (--i > lo) { - d = ds[i] + BIGRAD*d;
-
} -
dl = ds[i]; -
if (bits && (dl & (1UL << (bits %= BITSPERDIG)))) { - int carry = dl & ~(~0UL << bits);
- if (!carry) {
-
while (i-- > 0) { -
if ((carry = ds[i]) != 0) break; -
} - }
- if (carry) {
-
dl &= ~0UL << bits; -
dl += 1UL << bits; -
if (!dl) d += 1; - }
-
} -
d = dl + BIGRAD*d; -
if (lo) d = ldexp(d, lo * BITSPERDIG); - }
}
if (!RBIGNUM_SIGN(x)) d = -d;