diff options
Diffstat (limited to 'test/math/elog.c')
-rw-r--r-- | test/math/elog.c | 184 |
1 files changed, 92 insertions, 92 deletions
diff --git a/test/math/elog.c b/test/math/elog.c index 8afc1e5b4..bc517b197 100644 --- a/test/math/elog.c +++ b/test/math/elog.c @@ -1,92 +1,92 @@ -/* xlog.c */
-/* natural logarithm */
-/* by Stephen L. Moshier. */
-
-#include "mconf.h"
-#include "ehead.h"
-
-
-
-void elog( x, y )
-unsigned short *x, *y;
-{
-unsigned short xx[NE], z[NE], a[NE], b[NE], t[NE], qj[NE];
-long ex;
-int fex;
-
-
-if( x[NE-1] & (unsigned short )0x8000 )
- {
- eclear(y);
- mtherr( "elog", DOMAIN );
- return;
- }
-if( ecmp( x, ezero ) == 0 )
- {
- einfin( y );
- eneg(y);
- mtherr( "elog", SING );
- return;
- }
-if( ecmp( x, eone ) == 0 )
- {
- eclear( y );
- return;
- }
-
-/* range reduction: log x = log( 2**ex * m ) = ex * log2 + log m */
-efrexp( x, &fex, xx );
-/*
-emov(x, xx );
-ex = xx[NX-1] & 0x7fff;
-ex -= 0x3ffe;
-xx[NX-1] = 0x3ffe;
-*/
-
-/* Adjust range to 1/sqrt(2), sqrt(2) */
-esqrt2[NE-1] -= 1;
-if( ecmp( xx, esqrt2 ) < 0 )
- {
- fex -= 1;
- emul( xx, etwo, xx );
- }
-esqrt2[NE-1] += 1;
-
-esub( eone, xx, a );
-if( a[NE-1] == 0 )
- {
- eclear( y );
- goto logdon;
- }
-eadd( eone, xx, b );
-ediv( b, a, y ); /* store (x-1)/(x+1) in y */
-
-emul( y, y, z );
-
-emov( eone, a );
-emov( eone, b );
-emov( eone, qj );
-do
- {
- eadd( etwo, qj, qj ); /* 2 * i + 1 */
- emul( z, a, a );
- ediv( qj, a, t );
- eadd( t, b, b );
- }
-while( ((b[NE-1] & 0x7fff) - (t[NE-1] & 0x7fff)) < NBITS );
-
-
-emul( b, y, y );
-emul( y, etwo, y );
-
-logdon:
-
-/* now add log of 2**ex */
-if( fex != 0 )
- {
- ex = fex;
- ltoe( &ex, b );
- emul( elog2, b, b );
- eadd( b, y, y );
- }
-}
+/* xlog.c */ +/* natural logarithm */ +/* by Stephen L. Moshier. */ + +#include "mconf.h" +#include "ehead.h" + + + +void elog( x, y ) +unsigned short *x, *y; +{ +unsigned short xx[NE], z[NE], a[NE], b[NE], t[NE], qj[NE]; +long ex; +int fex; + + +if( x[NE-1] & (unsigned short )0x8000 ) + { + eclear(y); + mtherr( "elog", DOMAIN ); + return; + } +if( ecmp( x, ezero ) == 0 ) + { + einfin( y ); + eneg(y); + mtherr( "elog", SING ); + return; + } +if( ecmp( x, eone ) == 0 ) + { + eclear( y ); + return; + } + +/* range reduction: log x = log( 2**ex * m ) = ex * log2 + log m */ +efrexp( x, &fex, xx ); +/* +emov(x, xx ); +ex = xx[NX-1] & 0x7fff; +ex -= 0x3ffe; +xx[NX-1] = 0x3ffe; +*/ + +/* Adjust range to 1/sqrt(2), sqrt(2) */ +esqrt2[NE-1] -= 1; +if( ecmp( xx, esqrt2 ) < 0 ) + { + fex -= 1; + emul( xx, etwo, xx ); + } +esqrt2[NE-1] += 1; + +esub( eone, xx, a ); +if( a[NE-1] == 0 ) + { + eclear( y ); + goto logdon; + } +eadd( eone, xx, b ); +ediv( b, a, y ); /* store (x-1)/(x+1) in y */ + +emul( y, y, z ); + +emov( eone, a ); +emov( eone, b ); +emov( eone, qj ); +do + { + eadd( etwo, qj, qj ); /* 2 * i + 1 */ + emul( z, a, a ); + ediv( qj, a, t ); + eadd( t, b, b ); + } +while( ((b[NE-1] & 0x7fff) - (t[NE-1] & 0x7fff)) < NBITS ); + + +emul( b, y, y ); +emul( y, etwo, y ); + +logdon: + +/* now add log of 2**ex */ +if( fex != 0 ) + { + ex = fex; + ltoe( &ex, b ); + emul( elog2, b, b ); + eadd( b, y, y ); + } +} |