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Diffstat (limited to 'lib/libm/common_source/log10.c')
| -rw-r--r-- | lib/libm/common_source/log10.c | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/lib/libm/common_source/log10.c b/lib/libm/common_source/log10.c new file mode 100644 index 000000000000..d2617ccebb9e --- /dev/null +++ b/lib/libm/common_source/log10.c @@ -0,0 +1,95 @@ +/* + * Copyright (c) 1985, 1993 + * The Regents of the University of California. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef lint +static char sccsid[] = "@(#)log10.c 8.1 (Berkeley) 6/4/93"; +#endif /* not lint */ + +/* LOG10(X) + * RETURN THE BASE 10 LOGARITHM OF x + * DOUBLE PRECISION (VAX D format 56 bits, IEEE DOUBLE 53 BITS) + * CODED IN C BY K.C. NG, 1/20/85; + * REVISED BY K.C. NG on 1/23/85, 3/7/85, 4/16/85. + * + * Required kernel function: + * log(x) + * + * Method : + * log(x) + * log10(x) = --------- or [1/log(10)]*log(x) + * log(10) + * + * Note: + * [log(10)] rounded to 56 bits has error .0895 ulps, + * [1/log(10)] rounded to 53 bits has error .198 ulps; + * therefore, for better accuracy, in VAX D format, we divide + * log(x) by log(10), but in IEEE Double format, we multiply + * log(x) by [1/log(10)]. + * + * Special cases: + * log10(x) is NaN with signal if x < 0; + * log10(+INF) is +INF with no signal; log10(0) is -INF with signal; + * log10(NaN) is that NaN with no signal. + * + * Accuracy: + * log10(X) returns the exact log10(x) nearly rounded. In a test run + * with 1,536,000 random arguments on a VAX, the maximum observed + * error was 1.74 ulps (units in the last place). + * + * Constants: + * The hexadecimal values are the intended ones for the following constants. + * The decimal values may be used, provided that the compiler will convert + * from decimal to binary accurately enough to produce the hexadecimal values + * shown. + */ + +#include "mathimpl.h" + +vc(ln10hi, 2.3025850929940456790E0 ,5d8d,4113,a8ac,ddaa, 2, .935D8DDDAAA8AC) + +ic(ivln10, 4.3429448190325181667E-1, -2, 1.BCB7B1526E50E) + +#ifdef vccast +#define ln10hi vccast(ln10hi) +#endif + + +double log10(x) +double x; +{ +#if defined(vax)||defined(tahoe) + return(log(x)/ln10hi); +#else /* defined(vax)||defined(tahoe) */ + return(ivln10*log(x)); +#endif /* defined(vax)||defined(tahoe) */ +} |