Hi.
There are some possible optimizations for some methods.
For nextAfter(double,double) (same for float version), instead of testing
NaN-ity right away,
we can test most common (or at least regular) cases first:
public static double nextAfter(double start, double direction) {
// Balancing out by branching to going-down case first,
// for it is heavier than going-up case (test if start is +-0.0).
if (start > direction) {
// Going down.
if (start == 0.0d) {
// start is +0.0 or -0.0
return -Double.MIN_VALUE;
}
final long transducer = Double.doubleToRawLongBits(start);
assert transducer != 0L;
return Double.longBitsToDouble(transducer + ((transducer > 0L) ?
-1L:1L));
} else if (start < direction) {
// Going up.
// Add +0.0 to get rid of a -0.0 (+0.0 + -0.0 => +0.0)
// then bitwise convert start to integer.
final long transducer = Double.doubleToRawLongBits(start + 0.0d);
return Double.longBitsToDouble(transducer + ((transducer >= 0L) ?
1L:-1L));
} else if (start == direction) {
return direction;
} else { // start and/or direction is NaN
return start + direction;
}
}
Same for nextUp(double) and float version (also, testing transducer >= 0L
instead of d >= 0.0D seems to help):
public static double nextUp(double d) {
if (d < Double.POSITIVE_INFINITY) {
final long transducer = Double.doubleToRawLongBits(d + 0.0D);
return Double.longBitsToDouble(transducer + ((transducer >= 0L) ?
1L:-1L));
} else { // d is NaN or +Infinity
return d;
}
}
-Jeff
________________________________
De : "joe.da...@oracle.com" <joe.da...@oracle.com>
À : core-libs-dev <core-libs-dev@openjdk.java.net>
Envoyé le : Samedi 17 Septembre 2011 3h52
Objet : JDK 8 code review request for 7091682 "Move sun.misc.FpUtils code into
java.lang.Math"
Hello.
Please review the changes to address
7091682 "Move sun.misc.FpUtils code into java.lang.Math"
http://cr.openjdk.java.net/~darcy/7091682.0/
As implied by the synopsis, where appropriate JDK-implementation code used to
provide functionality in java.lang.Math and java.lang.StrictMath is moved out
of sun.misc.* and into java.lang.Math. Uses of methods available in
java.lang.Math and switched to that entry point as opposed to the sun.misc
one. Additionally, the sun.misc methods whose implementation was moved were
also deprecated.
Later in JDK 8, I will probably add some of the remaining un-deprecated methods
in sun.misc.FpUtils as java.lang.Math/StrictMath methods.
Thanks,
-Joe
