diff options
| author | Eric Andersen <andersen@codepoet.org> | 2001-10-02 10:45:16 +0000 |
|---|---|---|
| committer | Eric Andersen <andersen@codepoet.org> | 2001-10-02 10:45:16 +0000 |
| commit | f108799afa9b1d207e7139608c261f5546eb56bf (patch) | |
| tree | b84ad7a12eb961ca185c83b45098d5fc23ecd1ae /test/math/elog.c | |
| parent | 04dafe547980c50bef57b3ea7a4f9e3d81400a87 (diff) | |
Add in some math lib tests
Diffstat (limited to 'test/math/elog.c')
| -rw-r--r-- | test/math/elog.c | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/test/math/elog.c b/test/math/elog.c new file mode 100644 index 000000000..8afc1e5b4 --- /dev/null +++ b/test/math/elog.c @@ -0,0 +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 );
+ }
+}
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