diff options
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | stdlib/erand48_r.c | 32 |
2 files changed, 13 insertions, 24 deletions
@@ -1,3 +1,8 @@ +Sat Mar 16 20:58:43 1996 Roland McGrath <roland@charlie-brown.gnu.ai.mit.edu> + + * stdlib/erand48_r.c: Use FP division by powers of two to distribute + short bits into double. + Sat Mar 16 20:08:22 1996 David Mosberger-Tang <davidm@azstarnet.com> * sysdeps/alpha/memchr.S: new file. diff --git a/stdlib/erand48_r.c b/stdlib/erand48_r.c index ab41474..17caae5 100644 --- a/stdlib/erand48_r.c +++ b/stdlib/erand48_r.c @@ -18,45 +18,29 @@ not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include <stdlib.h> -#include "gmp.h" -#include "gmp-mparam.h" -#include <float.h> +#include <limits.h> -/* Function to construct a floating point number from an MP integer - containing the fraction bits, a base 2 exponent, and a sign flag. */ -extern double __mpn_construct_double (mp_srcptr mpn, int exponent, int neg); - int erand48_r (xsubi, buffer, result) unsigned short int xsubi[3]; struct drand48_data *buffer; double *result; { - mp_limb mpn[(3 * sizeof (unsigned short int) + sizeof (mp_limb) - 1) - / sizeof (mp_limb)]; - /* Compute next state. */ if (__drand48_iterate (xsubi, buffer) < 0) return -1; - /* Build a 48-bit mpn containing the 48 random bits. */ + /* Construct a positive double with the 48 random bits distributed over + its fractional part so the resulting FP number is [0.0,1.0). */ -#if BITS_PER_MP_LIMB == 64 - mpn[0] = (xsubi[0] << 32) | (xsubi[1] << 16) | xsubi[2]; -#elif BITS_PER_MP_LIMB == 32 - mpn[0] = (xsubi[1] << 16) | xsubi[2]; - mpn[1] = xsubi[0]; +#if USHRT_MAX == 65535 + *result = ((double) xsubi[2] / (1ULL << 48) + + (double) xsubi[1] / (1ULL << 32) + + (double) xsubi[0] / (1ULL << 16)); #else - #error "BITS_PER_MP_LIMB value not handled" +# error Unsupported size of short int #endif - /* Shift them up so they are most significant bits of the fraction. */ - __mpn_lshift (mpn, mpn, sizeof mpn / sizeof mpn[0], DBL_MANT_DIG - 48); - - /* Construct a positive double using those bits for the fractional part, - and a zero exponent so the resulting FP number is [0.0,1.0). */ - *result = __mpn_construct_double (mpn, 0, 0); - return 0; } |