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| author | Kevin Ryde <user42@zip.com.au> | 2000-03-18 23:59:32 +0100 |
|---|---|---|
| committer | Kevin Ryde <user42@zip.com.au> | 2000-03-18 23:59:32 +0100 |
| commit | 0f84121d0d38404c5db3622565f5ecd2eae9dcef (patch) | |
| tree | b95363453a50283d84bf36f46342e6e5ac20919e /mpn/generic | |
| parent | 6d01305df57fd6640dd88991f8d9cee8f7a62da3 (diff) | |
| download | gmp-0f84121d0d38404c5db3622565f5ecd2eae9dcef.tar.gz | |
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Diffstat (limited to 'mpn/generic')
| -rw-r--r-- | mpn/generic/diveby3.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/mpn/generic/diveby3.c b/mpn/generic/diveby3.c index 826960366..61ea04c86 100644 --- a/mpn/generic/diveby3.c +++ b/mpn/generic/diveby3.c @@ -25,7 +25,7 @@ the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. #include "gmp-impl.h" -#define MP_LIMB_T_MAX (((mp_limb_t) 0) - 1) +#define MP_LIMB_T_MAX (~((mp_limb_t) 0)) /* Multiplicative inverse of 3, modulo 2^BITS_PER_MP_LIMB. 0xAAAAAAAB for 32 bits, 0xAAAAAAAAAAAAAAAB for 64 bits. */ @@ -40,7 +40,12 @@ the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. with a fast mul but slowish div. The c += is adding the high word of 3*l to c. That high word will be 0, - 1 or 2. */ + 1 or 2. + + The quotient q and return value r satisfy r*b^n+a == 3*q, where a is the + dividend, n is the size of a and q, and b is the limb size, 2^32 or 2^64. + Clearly when r==0 this gives q==a/3, but the actual result when r!=0 + isn't documented at the moment. */ mp_limb_t #if __STDC__ |