Name: rmT116609 Date: 01/23/2003


FULL PRODUCT VERSION :
java version "1.4.1"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1-b21)
Java HotSpot(TM) Client VM (build 1.4.1-b21, mixed mode)


FULL OPERATING SYSTEM VERSION :
glibc-2.3.1-13
kernel 2.4.7-10
Redhat 7.2

Windows 2000


A DESCRIPTION OF THE PROBLEM :
There is a performance regression in Math.cos and Math.sin (and possibly other trig. functions I have not tested) between JDK 1.3.1 and JDK 1.4.1. Although I see Math functions such as exp and sqrt work significantly faster in
1.4.1 than in 1.3.1, sin and cos are 2.5 times slower in 1.4.1 than in 1.3.1. This is a large part of the reason for the performance regression reported in the benchmark at http://www.coyotegulch.com/reviews/almabench.html and widely
disseminated at various linux-oriented sites.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Run the attached microbenchmark under JDK 1.3.1 and JDK 1.4.1 on linux.

EXPECTED VERSUS ACTUAL BEHAVIOR :
Expected results:
All Math functions run at the same speed or faster under 1.4.1 when compared to 1.3.1

Actual results:
exp and sqrt do run faster, but sin and cos are significantly slower

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public class trigbench {
    public static void main(String [] args) {
double v = 0;
double t = 0;
int n = 30000000;
// Warmup JIT
for (int i = 0; i < n; i++) {
double m = v%(2*Math.PI);
t += e(m)*f(m)*g(m)*h(m);
v += 0.1;
}
long tStart, tEnd;

tStart = System.currentTimeMillis();
for (int i = 0; i < n; i++) {
t += e(v%(2*Math.PI));
v += 0.1;
}
tEnd = System.currentTimeMillis();
System.out.println("Time for cos (s):"+(tEnd-tStart)/1000.0);

tStart = System.currentTimeMillis();
for (int i = 0; i < n; i++) {
t += f(v%(2*Math.PI));
v += 0.1;
}
tEnd = System.currentTimeMillis();
System.out.println("Time for sin (s):"+(tEnd-tStart)/1000.0);

tStart = System.currentTimeMillis();
for (int i = 0; i < n; i++) {
t += g(v%(2*Math.PI));
v += 0.1;
}
tEnd = System.currentTimeMillis();
System.out.println("Time for exp (s):"+(tEnd-tStart)/1000.0);

tStart = System.currentTimeMillis();
for (int i = 0; i < n; i++) {
t += h(v%(2*Math.PI));
v += 0.1;
}
tEnd = System.currentTimeMillis();
System.out.println("Time for sqrt (s):"+(tEnd-tStart)/1000.0);

// Print result to disallow certain optimizations
System.out.println("Result:"+t);
    }

    public static double e(double v) {
double result = Math.cos(v);
return result;
    }

    public static double f(double v) {
double result = Math.sin(v);
return result;
    }

    public static double g(double v) {
double result = Math.exp(v);
return result;
    }

    public static double h(double v) {
double result = Math.sqrt(v);
return result;
    }
}

---------- END SOURCE ----------

CUSTOMER WORKAROUND :
Use 1.3.1 or code up approximations to the trig functions.

Release Regression From : 1.3.1_06
The above release value was the last known release where this
bug was known to work. Since then there has been a regression.

(Review ID: 179610)
======================================================================