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/etanh.c | |
| parent | 04dafe547980c50bef57b3ea7a4f9e3d81400a87 (diff) | |
Add in some math lib tests
Diffstat (limited to 'test/math/etanh.c')
| -rw-r--r-- | test/math/etanh.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/test/math/etanh.c b/test/math/etanh.c new file mode 100644 index 000000000..c74b4700a --- /dev/null +++ b/test/math/etanh.c @@ -0,0 +1,52 @@ +/* xtanh.c */
+/* hyperbolic tangent check routine */
+/* this subroutine is used by the exponential function routine */
+/* by Stephen L. Moshier. */
+
+
+
+#include "ehead.h"
+
+
+void etanh( x, y )
+unsigned short *x, *y;
+{
+unsigned short e[NE], r[NE], j[NE], xx[NE], m2[NE];
+short i, n;
+long lj;
+
+emov( x, r );
+r[NE-1] &= (unsigned short )0x7fff;
+if( ecmp(r, eone) >= 0 )
+ {
+/* tanh(x) = (exp(x) - exp(-x)) / (exp(x) + exp(-x))
+ * Note eexp() calls xtanh, but with an argument less than (1 + log 2)/2.
+ */
+ eexp( r, e );
+ ediv( e, eone, r );
+ esub( r, e, xx );
+ eadd( r, e, j );
+ ediv( j, xx, y );
+ return;
+ }
+
+emov( etwo, m2 );
+eneg( m2 );
+
+n = NBITS/8; /* Number of terms to do in the continued fraction */
+lj = 2 * n + 1;
+ltoe( &lj, j );
+
+emov( j, e );
+emul( x, x, xx );
+
+/* continued fraction */
+for( i=0; i<n; i++)
+ {
+ ediv( e, xx, r );
+ eadd( m2, j, j );
+ eadd( r, j, e );
+ }
+
+ediv( e, x, y );
+}
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