Re: Don't optimize by hand (Was Re: Lack of fabsf on Solaris(patch included))

[Kazuyuki Shudo <shudoh at muraoka dot info dot waseda dot ac dot jp>]

Andrew Haley wrote:

> > And we probably don't really implement strict fp
> > semantics anyway
>
> The last time that I ran any tests we were 100% strict fp perfect.
> That's better than the other Java implementation I tried!
>
> Andrew.

Here is a test program.
If the Java runtime is compliant with the strictfp specification,
you will see the following:

  % java StrictfpTest
    shuJIT  for Sun Classic VM/x86  by Kazuyuki Shudo
  1.112808544714844E-308 (0x0008008000000000)
    * 1.0000000000000002 (0x3ff0000000000001)
  default : 1.112808544714844E-308 (0x8008000000000)
  strictfp: 1.1128085447148447E-308 (0x8008000000001)

  2.225073858507201E-308 (0x000fffffffffffff)
    / 0.9999999999999999 (0x3fefffffffffffff)
  default : 2.2250738585072014E-308 (0x10000000000000)
  strictfp: 2.225073858507201E-308 (0xfffffffffffff)

I guess the FP semantics has not been implemented on GCJ yet.

Kazuyuki SHUDO				Happy Hacking!
  Muraoka Laboratory, Waseda University
class StrictfpTest {
  private static double defaultDmul(double a, double b) {
    return a * b;
  }
  private static strictfp double strictDmul(double a, double b) {
    return a * b;
  }
  private static double defaultDdiv(double a, double b) {
    return a / b;
  }
  private static strictfp double strictDdiv(double a, double b) {
    return a / b;
  }

  public static void main(String[] args) {
    double a, b, c;

    /* multiplication */
    a = Double.longBitsToDouble(0x0008008000000000L);
    b = Double.longBitsToDouble(0x3ff0000000000001L);

    System.out.println(a + " (0x0008008000000000)");
    System.out.println("  * " + b + " (0x3ff0000000000001)");

    c = defaultDmul(a, b);
    System.out.println("default : " + c +
		" (0x" + Long.toHexString(Double.doubleToLongBits(c)) + ")");

    c = strictDmul(a, b);
    System.out.println("strictfp: " + c +
		" (0x" + Long.toHexString(Double.doubleToLongBits(c)) + ")");

    System.out.println();

    /* division */
    a = Double.longBitsToDouble(0x000fffffffffffffL);
    b = Double.longBitsToDouble(0x3fefffffffffffffL);

    System.out.println(a + " (0x000fffffffffffff)");
    System.out.println("  / " + b + " (0x3fefffffffffffff)");

    c = defaultDdiv(a, b);
    System.out.println("default : " + c +
		" (0x" + Long.toHexString(Double.doubleToLongBits(c)) + ")");

    c = strictDdiv(a, b);
    System.out.println("strictfp: " + c +
		" (0x" + Long.toHexString(Double.doubleToLongBits(c)) + ")");
  }
}