Problem with sqrt

[iyersathya]

Hello Udo,
Thank you producing such a useful library.
I came across an issue where sqrt function is getting stuck in this loop.
do {
ixPrev = ix;
ix = ix.add(n.divide(ix)).shiftRight(1);
// Give other threads a chance to work;
Thread.yield();
} while (ix.compareTo(ixPrev) != 0);

I ended up overriding the function with java's sqrtj implementation.

[uklimaschewski]

Thank you for the feedback, can you give me an example expression that reproduces this?

[iyersathya]

please try SRRT(24)

[iyersathya]

My mistake, I think it will only work on perfect squares.

[squeek502]

SQRT(24) seems to work fine for me. Adding

assertEquals("4.8989794", new Expression("SQRT(24)").eval().toPlainString());

to the existing SQRT tests still passes.

[uklimaschewski]

What kind of Java and machine are you using? I tested in on a 64bit Intel Windows machine, without problem.

[iyersathya]

I am using mac pro (2.6 GHz Intel Core i7), Yes running junit tests on native machine works fine.
I am using Android's emulator on genymotion (ARM hypervisor), I also tried it on Samsung Galaxy 7 note ( ARM) and it gets stuck in a while loop.
Since its android , it is running on Dalvik VM, and the code is Dex'ed Dalvik code.
do { ixPrev = ix; ix = ix.add(n.divide(ix)).shiftRight(1); // Give other threads a chance to work; Thread.yield(); } while (ix.compareTo(ixPrev) != 0);
here's the loop result.
loop 1:
ixPrev=ix=4
ix = 5
loop 2:
ixPrev = ix = 5;
ix = 4
loop 3:
ixPrev=ix=4
ix=5

Hope that helps.

[uklimaschewski]

I have now tried out 4 different Android devices and 2 different emulator configurations, but I was unable to reproduce. I'll close this issue for now. If there is a way how I can reproduce this bug here, let me know.