Bill,
This looks like nice work.
Have you considered contributing the code back to Java itself?
On Tue, Jun 8, 2010 at 8:29 AM, Bill Rossi <b...@rossi.com> wrote:
>
> I've looked at StrictMath, generally Math appears to delegates to
> StrictMath. StrictMath is implemented by the C fdlibm library.
>
> This is what I've implemented to date, the code will compile and run
> on JDK 1.4 and later. It may work on older JDKs, but I don't have them
> available for testing. Note that functions like expm1 are not available
> in earlier JDKs.
>
> public class FastMath extends java.lang.Object{
> public FastMath();
> public static double exp(double);
> public static double expm1(double);
> public static double log(double);
> public static double log1p(double);
> public static double log10(double);
> public static double pow(double, double);
> public static double sin(double);
> public static double cos(double);
> public static double tan(double);
> public static double atan(double);
> public static double atan2(double, double);
> public static double toRadians(double);
> public static double toDegrees(double);
> public static double abs(double);
> public static double ulp(double);
> public static double floor(double);
> public static double ceil(double);
> public static double rint(double);
> public static long round(double);
> static {};
> }
>
> Performance test gives these results:
>
> Function Time Result Function Time
> Result
>
> ----------------------------------------------------------------------------------------------
> StrictMath.log 967 1.5118099917827207E8 FastMath.log 553
> 1.5118099917827207E8
> StrictMath.pow 3199 4.6455095486440872E16 FastMath.pow 1967
> 4.645509548644088E16
> StrictMath.exp 1079 2.2025454782076317E10 FastMath.exp 562
> 2.2025454782076317E10
> StrictMath.sin 1151 1839071.8010869955 FastMath.sin 766
> 1839071.8010869955
> StrictMath.cos 1173 -544020.191353572 FastMath.cos 665
> -544020.191353572
> StrictMath.tan 1568 -5.024600819552688E7 FastMath.tan 1081
> -5.024600819552688E7
> StrictMath.atan 1079 1.2403715749052648E7 FastMath.atan 902
> 1.2403715749052648E7
> StrictMath.expm1 727 -9899999.500018543 FastMath.expm1 773
> -9899999.500018543
>
> This table shows execution time for 10,000,000 calls in milliseconds. The
> result printed is there to prevent the JIT from optimizing away the
> calculation entirely.
>
> Note that some functions such as exp are nearly twice as fast. I've seen
> it 3 times faster on different processors. The preformance varies by the
> relative speed of calculation vs memory lookups.
>
> The functions are implemented as tables of values in extra precision
> (approx 70 bits), and then interpolated with a minimax polynomial.
>
> Typical test code:
>
> x = 0;
> time = System.currentTimeMillis();
> for (int i=0; i<10000000; i++)
> x+=StrictMath.exp(i/1000000.0);
> time = System.currentTimeMillis() - time;
> System.out.print("StrictMath.exp "+time+"\t"+x+"\t");
>
> x = 0;
> time = System.currentTimeMillis();
> for (int i=0; i<10000000; i++)
> x+=FastMath.exp(i/1000000.0);
> time = System.currentTimeMillis() - time;
> System.out.println("FastMath.exp "+time+"\t"+x);
>
> To test accuracy, I'd compute results and compare them to an aribitrary
> precision math library.
>
>
> On Tue, 8 Jun 2010, James Carman wrote:
>
> Have you tried looking at StrictMath?
>>
>> On Tue, Jun 8, 2010 at 10:44 AM, Ted Dunning <ted.dunn...@gmail.com>
>> wrote:
>>
>>> Bill,
>>>
>>> Which functions do you have?
>>>
>>> Anything more than the standard sin, cos, exp and log?
>>>
>>>
>>> On Tue, Jun 8, 2010 at 6:52 AM, Bill Rossi <b...@rossi.com> wrote:
>>>
>>> I have developed over the past year a set of elementary functions
>>>> similar
>>>> to those in java.lang.Math, but with the following characteristics:
>>>>
>>>> * Higher performance.
>>>> * Better accuracy. Results are accurate to slightly more that +/- 0.5
>>>> ULP.
>>>> * Pure Java. The standard Math class is impleneted via JNI, and thus
>>>> takes
>>>> a performance hit.
>>>>
>>>>
>>>
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