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start of quick-n-dirty 128-bit math lib

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git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@9979 57a11ea4-9604-0410-9ed3-97b8803252fd
This commit is contained in:
Linas Vepstas 2004-05-30 00:18:34 +00:00
parent c5c92f5099
commit 28fa53b187
1 changed files with 103 additions and 0 deletions
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103
src/engine/gnc-numeric.c
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@ -40,6 +40,108 @@
/* static short module = MOD_ENGINE; */
/* =============================================================== */
/* Quick-n-dirty 128-bit math lib */
typedef struct {
gint64 hi;
guint64 lo;
} gncint128;
static inline gncint128
mult (gint64 a, gint64 b)
{
gncint128 prod;
short aneg=0, bneg=0;
if (0>a)
{
aneg = 1;
a = -a;
}
if (0>b)
{
bneg = 1;
b = -b;
}
guint64 a1 = a >> 32;
guint64 a0 = a - (a1<<32);
guint64 b1 = b >> 32;
guint64 b0 = b - (b1<<32);
guint64 d = a0*b0;
guint64 d1 = d >> 32;
guint64 d0 = d - (d1<<32);
guint64 e = a0*b1;
guint64 e1 = e >> 32;
guint64 e0 = e - (e1<<32);
guint64 f = a1*b0;
guint64 f1 = f >> 32;
guint64 f0 = f - (f1<<32);
guint64 g = a1*b1;
guint64 g1 = g >> 32;
guint64 g0 = g - (g1<<32);
guint64 sum = d1+e0+f0;
guint64 carry = 0;
/* Can't say 1<<32 cause cpp will goof it up; 1ULL<<32 might work */
guint64 roll = 1<<30;
roll <<= 2;
guint64 pmax = roll-1;
while (pmax < sum)
{
sum -= roll;
carry ++;
}
prod.lo = d0 + (sum<<32);
prod.hi = carry + e1 + f1 + g0 + (g1<<32);
if (aneg) prod.hi = -prod.hi;
if (bneg) prod.hi = -prod.hi;
return prod;
}
#ifdef TEST_128_BIT_MULT
void pr (gint64 a, gint64 b)
{
gncint128 prod = mult (a,b);
printf ("%lld * %lld = %lld %llu (0x%llx %llx)\n", a,b, prod.hi, prod.lo, prod.hi, prod.lo);
}
main ()
{
pr (2,2);
gint64 x = 1<<30;
x <<= 2;
pr (x,x);
pr (x+1,x);
pr (x+1,x+1);
pr (x,-x);
pr (-x,-x);
pr (x-1,x);
pr (x-1,x-1);
pr (x-2,x-2);
x <<= 1;
pr (x,x);
pr (x,-x);
}
#endif /* TEST_128_BIT_MULT */
/* =============================================================== */
#if 0
static const char * _numeric_error_strings[] =
{
@ -53,6 +155,7 @@ static const char * _numeric_error_strings[] =
static gint64 gnc_numeric_lcd(gnc_numeric a, gnc_numeric b);
/* =============================================================== */
/* This function is small, simple, and used everywhere below,
* lets try to inline it.
*/