# Rb\_big\_pow

**URL:** <https://www.ruby-forum.com/t/rb-big-pow/109480>\
**Category:** Development\
**Created:** [July 15, 2007, 4:38pm UTC](https://www.ruby-forum.com/t/rb-big-pow/109480 "2007-07-15T16:38:48Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [July 15, 2007, 4:38pm UTC](https://www.ruby-forum.com/t/rb-big-pow/109480/1 "2007-07-15T16:38:48Z")

</div>

e$B$U$He(B test\_integer.rb e$B$N\<B9T$re(B callgrind  
e$B$r$+$1$F!"e(Bbignum.c  
e$B$rD/$a$F$$$k$H!“e(Brb\_big\_pow e$B$NCf$K\<B9T$5$l$J$$ItJ,$,$”$k$N$Ke(B  
e$B5$$,$D$-$^$7$?!#$=$7$F$7$P$i$/D/$a$?7k2L!“e(Bn e$B$H$$$&JQ?t$O$:$Ce(B  
e$B$He(B 1 e$B$J$3$H$K5$$,$D$$$F$7$^$$$^$7$?!#$J$K$+JQ$@$H;W$&$s$G$9e(B  
e$B$,!”$I$&$J$s$G$7$g$&e(B?

…  
case T\_FIXNUM:  
yy = FIX2LONG(y);  
if (yy \> 0) {  
VALUE z = 0;  
SIGNED\_VALUE mask, n = 1; // e$B$3$3$Ge(B 1 e$B$r@\_Dje(B  
…  
for (mask = FIXNUM\_MAX + 1; mask; mask \>\>= 1) {  
if (!z) {  
SIGNED\_VALUE n2 = n \* n; // 1 \* 1 e$B$Oe(B 1  
if (!POSFIXABLE(n2) || (n2 / n != n)) { //  
e$B\>r7o$O@.N)$7$J$$e(B  
z = bigtrunc(bigsqr(rb\_int2big(n))); //  
e$B$3$3$O\<B9T$5$l$J$$e(B  
}  
else {  
n = n2; // e$B$3$3$Ge(B 1 e$B$rBeF~e(B  
}  
}  
else {  
z = bigtrunc(bigsqr(z));  
}  
if (yy & mask) {  
if (!z) z = rb\_int2big(n); //  
rb\_int2bige$B$K$O\>o$Ke(B 1 e$B$rEO$9e(B  
z = bigtrunc(rb\_big\_mul0(z, x));  
}  
}  
return bignorm(z);  
}  
d = (double)yy;  
break;  
…

---

<div class="post-metadata">

**Author:** ![Tanaka\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/c67d28/32.png) [@Tanaka\_A](https://www.ruby-forum.com/u/Tanaka_A)\
**Post date:** [July 15, 2007, 5:13pm UTC](https://www.ruby-forum.com/t/rb-big-pow/109480/2 "2007-07-15T17:13:51Z")

</div>

e$B$J$+$@$G$9!#e(B

At Sun, 15 Jul 2007 23:37:08 +0900,  
Tanaka A. wrote in [ruby-dev:31236]:

> e$B$U$He(B test\_integer.rb e$B$N\<B9T$re(B callgrind e$B$r$+$1$F!"e(Bbignum.c  
> e$B$rD/$a$F$$$k$H!“e(Brb\_big\_pow e$B$NCf$K\<B9T$5$l$J$$ItJ,$,$”$k$N$Ke(B  
> e$B5$$,$D$-$^$7$?!#$=$7$F$7$P$i$/D/$a$?7k2L!“e(Bn e$B$H$$$&JQ?t$O$:$Ce(B  
> e$B$He(B 1 e$B$J$3$H$K5$$,$D$$$F$7$^$$$^$7$?!#$J$K$+JQ$@$H;W$&$s$G$9e(B  
> e$B$,!”$I$&$J$s$G$7$g$&e(B?

e$B$?$7$+$KITMW$N$h$&$G$9!#e(B

> ```
> z = bigtrunc(bigsqr(z));
> }
> if (yy & mask) {
> if (!z) z = rb_int2big(n); // rb_int2bige$B$K$O>o$Ke(B 1 e$B$rEO$9e(B
> z = bigtrunc(rb_big_mul0(z, x));
> 
> ```

e$BK\Mh$J$i$3$3$Ge(Bne$B$Ke(Bxe$B$r3]$1$k$O$:$J$N$G$9$,!“e(Bxe$B$Oe(BBignume$B$J$N$Ge(BBignum  
e$B$G$”$ke(Bze$B$r:G=i$+$i;H$&$3$H$K$J$j!“e(BFixnume$BAjEv$Ne(Bne$B$O;H$o$l$k$3$H$,e(B  
e$B$J$/$J$C$F$7$^$C$?!”$H$$$&$3$H$+$H;W$$$^$9!#e(B