mirror of
https://github.com/ruby/ruby.git
synced 2022-11-09 12:17:21 -05:00
* ext/bigdecimal/bigdecimal.c: fix rounding algorithms for half-down
and half-even. This change is based on the patch created by Matthew Willson, the reporter of this bug. [Bug #3803] [ruby-core:32136] * test/bigdecimal/test_bigdecimal.rb: add tests for above changes. git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@29293 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
mrkn
parent
9dffbcfc09
commit
3cbda570c2
3 changed files with 130 additions and 53 deletions
|
|
@ -1,3 +1,11 @@
|
|||
Sun Sep 19 05:14:35 2010 Kenta Murata <mrkn@mrkn.jp>
|
||||
|
||||
* ext/bigdecimal/bigdecimal.c: fix rounding algorithms for half-down
|
||||
and half-even. This change is based on the patch created by Matthew
|
||||
Willson, the reporter of this bug. [Bug #3803] [ruby-core:32136]
|
||||
|
||||
* test/bigdecimal/test_bigdecimal.rb: add tests for above changes.
|
||||
|
||||
Sat Sep 18 20:09:51 2010 Tanaka Akira <akr@fsij.org>
|
||||
|
||||
* ext/pathname/pathname.c (path_each_entry): Pathname#each_entry
|
||||
|
|
|
|||
|
|
@ -308,9 +308,9 @@ BigDecimal_load(VALUE self, VALUE str)
|
|||
*
|
||||
* ROUND_UP:: round away from zero
|
||||
* ROUND_DOWN:: round towards zero (truncate)
|
||||
* ROUND_HALF_UP:: round up if the appropriate digit >= 5, otherwise truncate (default)
|
||||
* ROUND_HALF_DOWN:: round up if the appropriate digit >= 6, otherwise truncate
|
||||
* ROUND_HALF_EVEN:: round towards the even neighbor (Banker's rounding)
|
||||
* ROUND_HALF_UP:: round towards the nearest neighbor, unless both neighbors are equidistant, in which case round away from zero. (default)
|
||||
* ROUND_HALF_DOWN:: round towards the nearest neighbor, unless both neighbors are equidistant, in which case round towards zero.
|
||||
* ROUND_HALF_EVEN:: round towards the nearest neighbor, unless both neighbors are equidistant, in which case round towards the even neighbor (Banker's rounding)
|
||||
* ROUND_CEILING:: round towards positive infinity (ceil)
|
||||
* ROUND_FLOOR:: round towards negative infinity (floor)
|
||||
*
|
||||
|
|
@ -4559,8 +4559,9 @@ VpMidRound(Real *y, unsigned short f, ssize_t nf)
|
|||
*/
|
||||
{
|
||||
/* fracf: any positive digit under rounding position? */
|
||||
/* fracf_1further: any positive digits under one further than the rounding position? */
|
||||
/* exptoadd: number of digits needed to compensate negative nf */
|
||||
int fracf;
|
||||
int fracf, fracf_1further;
|
||||
ssize_t n,i,ix,ioffset, exptoadd;
|
||||
BDIGIT v, shifter;
|
||||
BDIGIT div;
|
||||
|
|
@ -4573,62 +4574,111 @@ VpMidRound(Real *y, unsigned short f, ssize_t nf)
|
|||
VpSetZero(y,VpGetSign(y)); /* truncate everything */
|
||||
return 0;
|
||||
}
|
||||
exptoadd = -nf;
|
||||
nf = 0;
|
||||
exptoadd = -nf;
|
||||
nf = 0;
|
||||
}
|
||||
|
||||
/* ix: x->fraq[ix] contains round position */
|
||||
ix = nf / (ssize_t)BASE_FIG;
|
||||
if ((size_t)ix >= y->Prec) return 0; /* rounding position too right(small). */
|
||||
ioffset = nf - ix*(ssize_t)BASE_FIG;
|
||||
|
||||
v = y->frac[ix];
|
||||
|
||||
/* drop digits after pointed digit */
|
||||
ioffset = nf - ix*(ssize_t)BASE_FIG;
|
||||
n = (ssize_t)BASE_FIG - ioffset - 1;
|
||||
for (shifter=1,i=0; i<n; ++i) shifter *= 10;
|
||||
|
||||
/* so the representation used (in y->frac) is an array of BDIGIT, where
|
||||
each BDIGIT contains a value between 0 and BASE-1, consisting of BASE_FIG
|
||||
decimal places.
|
||||
|
||||
(that numbers of decimal places are typed as ssize_t is somewhat confusing)
|
||||
|
||||
nf is now position (in decimal places) of the digit from the start of
|
||||
the array.
|
||||
ix is the position (in BDIGITS) of the BDIGIT containing the decimal digit,
|
||||
from the start of the array.
|
||||
v is the value of this BDIGIT
|
||||
ioffset is the number of extra decimal places along of this decimal digit
|
||||
within v.
|
||||
n is the number of decimal digits remaining within v after this decimal digit
|
||||
shifter is 10**n,
|
||||
v % shifter are the remaining digits within v
|
||||
v % (shifter * 10) are the digit together with the remaining digits within v
|
||||
v / shifter are the digit's predecessors together with the digit
|
||||
div = v / shifter / 10 is just the digit's precessors
|
||||
(v / shifter) - div*10 is just the digit, which is what v ends up being reassigned to.
|
||||
*/
|
||||
|
||||
fracf = (v % (shifter * 10) > 0);
|
||||
fracf_1further = ((v % shifter) > 0);
|
||||
|
||||
v /= shifter;
|
||||
div = v / 10;
|
||||
v = v - div*10;
|
||||
if (fracf == 0) {
|
||||
for (i=ix+1; (size_t)i < y->Prec; i++) {
|
||||
if (y->frac[i] % BASE) {
|
||||
fracf = 1;
|
||||
break;
|
||||
}
|
||||
}
|
||||
/* now v is just the digit required.
|
||||
now fracf is whether the digit or any of the remaining digits within v are non-zero
|
||||
now fracf_1further is whether any of the remaining digits within v are non-zero
|
||||
*/
|
||||
|
||||
/* now check all the remaining BDIGITS for zero-ness a whole BDIGIT at a time.
|
||||
if we spot any non-zeroness, that means that we foudn a positive digit under
|
||||
rounding position, and we also found a positive digit under one further than
|
||||
the rounding position, so both searches (to see if any such non-zero digit exists)
|
||||
can stop */
|
||||
|
||||
for (i=ix+1; (size_t)i < y->Prec; i++) {
|
||||
if (y->frac[i] % BASE) {
|
||||
fracf = fracf_1further = 1;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
/* now fracf = does any positive digit exist under the rounding position?
|
||||
now fracf_1further = does any positive digit exist under one further than the
|
||||
rounding position?
|
||||
now v = the first digit under the rounding position */
|
||||
|
||||
/* drop digits after pointed digit */
|
||||
memset(y->frac+ix+1, 0, (y->Prec - (ix+1)) * sizeof(BDIGIT));
|
||||
|
||||
switch(f) {
|
||||
case VP_ROUND_DOWN: /* Truncate */
|
||||
break;
|
||||
case VP_ROUND_UP: /* Roundup */
|
||||
if (fracf) ++div;
|
||||
break;
|
||||
case VP_ROUND_HALF_UP: /* Round half up */
|
||||
break;
|
||||
case VP_ROUND_HALF_UP:
|
||||
if (v>=5) ++div;
|
||||
break;
|
||||
case VP_ROUND_HALF_DOWN: /* Round half down */
|
||||
if (v>=6) ++div;
|
||||
case VP_ROUND_HALF_DOWN:
|
||||
if (v > 5 || (v == 5 && fracf_1further)) ++div;
|
||||
break;
|
||||
case VP_ROUND_CEIL: /* ceil */
|
||||
case VP_ROUND_CEIL:
|
||||
if (fracf && (VpGetSign(y)>0)) ++div;
|
||||
break;
|
||||
case VP_ROUND_FLOOR: /* floor */
|
||||
case VP_ROUND_FLOOR:
|
||||
if (fracf && (VpGetSign(y)<0)) ++div;
|
||||
break;
|
||||
case VP_ROUND_HALF_EVEN: /* Banker's rounding */
|
||||
if (v>5) ++div;
|
||||
else if (v==5) {
|
||||
if ((size_t)i == (BASE_FIG-1)) {
|
||||
if (ix && (y->frac[ix-1]%2)) ++div;
|
||||
}
|
||||
if (v > 5) ++div;
|
||||
else if (v == 5) {
|
||||
if (fracf_1further) {
|
||||
++div;
|
||||
}
|
||||
else {
|
||||
if (div%2) ++div;
|
||||
}
|
||||
}
|
||||
break;
|
||||
if (ioffset == 0) {
|
||||
/* v is the first decimal digit of its BDIGIT;
|
||||
need to grab the previous BDIGIT if present
|
||||
to check for evenness of the previous decimal
|
||||
digit (which is same as that of the BDIGIT since
|
||||
base 10 has a factor of 2) */
|
||||
if (ix && (y->frac[ix-1] % 2)) ++div;
|
||||
}
|
||||
else {
|
||||
if (div % 2) ++div;
|
||||
}
|
||||
}
|
||||
}
|
||||
break;
|
||||
}
|
||||
for (i=0; i<=n; ++i) div *= 10;
|
||||
if (div>=BASE) {
|
||||
|
|
@ -4694,6 +4744,8 @@ VpLimitRound(Real *c, size_t ixDigit)
|
|||
return VpLeftRound(c, (int)VpGetRoundMode(), (ssize_t)ix);
|
||||
}
|
||||
|
||||
/* If I understand correctly, this is only ever used to round off the final decimal
|
||||
digit of precision */
|
||||
static void
|
||||
VpInternalRound(Real *c, size_t ixDigit, BDIGIT vPrev, BDIGIT v)
|
||||
{
|
||||
|
|
@ -4701,36 +4753,41 @@ VpInternalRound(Real *c, size_t ixDigit, BDIGIT vPrev, BDIGIT v)
|
|||
|
||||
unsigned short const rounding_mode = VpGetRoundMode();
|
||||
|
||||
if(VpLimitRound(c,ixDigit)) return;
|
||||
if(!v) return;
|
||||
if (VpLimitRound(c, ixDigit)) return;
|
||||
if (!v) return;
|
||||
|
||||
v /= BASE1;
|
||||
switch (rounding_mode) {
|
||||
case VP_ROUND_DOWN:
|
||||
break;
|
||||
break;
|
||||
case VP_ROUND_UP:
|
||||
if(v) f = 1;
|
||||
break;
|
||||
if (v) f = 1;
|
||||
break;
|
||||
case VP_ROUND_HALF_UP:
|
||||
if(v >= 5) f = 1;
|
||||
break;
|
||||
if (v >= 5) f = 1;
|
||||
break;
|
||||
case VP_ROUND_HALF_DOWN:
|
||||
if(v >= 6) f = 1;
|
||||
break;
|
||||
case VP_ROUND_CEIL: /* ceil */
|
||||
if(v && (VpGetSign(c)>0)) f = 1;
|
||||
break;
|
||||
case VP_ROUND_FLOOR: /* floor */
|
||||
if(v && (VpGetSign(c)<0)) f = 1;
|
||||
break;
|
||||
/* this is ok - because this is the last digit of precision,
|
||||
the case where v == 5 and some further digits are nonzero
|
||||
will never occur */
|
||||
if (v >= 6) f = 1;
|
||||
break;
|
||||
case VP_ROUND_CEIL:
|
||||
if (v && (VpGetSign(c) > 0)) f = 1;
|
||||
break;
|
||||
case VP_ROUND_FLOOR:
|
||||
if (v && (VpGetSign(c) < 0)) f = 1;
|
||||
break;
|
||||
case VP_ROUND_HALF_EVEN: /* Banker's rounding */
|
||||
if(v>5) f = 1;
|
||||
else if(v==5 && vPrev%2) f = 1;
|
||||
break;
|
||||
/* as per VP_ROUND_HALF_DOWN, because this is the last digit of precision,
|
||||
there is no case to worry about where v == 5 and some further digits are nonzero */
|
||||
if (v > 5) f = 1;
|
||||
else if (v == 5 && vPrev % 2) f = 1;
|
||||
break;
|
||||
}
|
||||
if(f) {
|
||||
VpRdup(c,ixDigit); /* round up */
|
||||
VpNmlz(c);
|
||||
if (f) {
|
||||
VpRdup(c, ixDigit);
|
||||
VpNmlz(c);
|
||||
}
|
||||
}
|
||||
|
||||
|
|
|
|||
|
|
@ -612,6 +612,18 @@ class TestBigDecimal < Test::Unit::TestCase
|
|||
assert_equal(3, x.round(0, BigDecimal::ROUND_CEILING))
|
||||
assert_equal(2, x.round(0, BigDecimal::ROUND_FLOOR))
|
||||
assert_raise(TypeError) { x.round(0, 256) }
|
||||
|
||||
15.times do |n|
|
||||
x = BigDecimal.new("5#{'0'*n}1")
|
||||
assert_equal(10**(n+2), x.round(-(n+2), BigDecimal::ROUND_HALF_DOWN))
|
||||
assert_equal(10**(n+2), x.round(-(n+2), BigDecimal::ROUND_HALF_EVEN))
|
||||
x = BigDecimal.new("0.5#{'0'*n}1")
|
||||
assert_equal(1, x.round(0, BigDecimal::ROUND_HALF_DOWN))
|
||||
assert_equal(1, x.round(0, BigDecimal::ROUND_HALF_EVEN))
|
||||
x = BigDecimal.new("-0.5#{'0'*n}1")
|
||||
assert_equal(-1, x.round(0, BigDecimal::ROUND_HALF_DOWN))
|
||||
assert_equal(-1, x.round(0, BigDecimal::ROUND_HALF_EVEN))
|
||||
end
|
||||
end
|
||||
|
||||
def test_truncate
|
||||
|
|
|
|||
Loading…
Reference in a new issue