Nbody Release 1.62
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Sidd
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Message 64767 - Posted: 28 Jun 2016, 17:44:03 UTC

Hey All,

I just released a new version of nbody, v1.62. In this release we did a few things:

We realized that different platforms were giving slightly different results. This was a problem as it would throw off the search algorithm and also may cause validation issues. Turns out there were an number of reasons for this. One was that the likelihood calculation was performed using single precision on a double precision application. So we changed it to be a double precision calculation.

Also, and most prominently, we realized that the windows command prompt and unix terminal read in inputs with different precision. One would cut the value of after about the 10th decimal place. This mean the actual input parameters were slightly different! Therefore, we forced the rounding of the input parameters after the 9th decimal place. That seemed to do the trick mostly.

Finally, we realized that our building mechanism was not building linux binaries statically. When we tried with our current mechanism we ran into a can of worms known as seg faults. It was a nightmare trying to find it so we decided to temporarily switch our building mechanism. I tested them on all our computers and it seems to work. But, as always, let me know if something goes awry.



Thanks everyone for your continued support!
Sidd

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Message 64768 - Posted: 28 Jun 2016, 17:51:32 UTC - in response to Message 64767.

Is that the reason no N-Body work has been available for quite some time?

If so, is that going to be remedied soon?
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Sidd
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Message 64769 - Posted: 28 Jun 2016, 17:59:42 UTC - in response to Message 64768.

Hey,

I am not entirely sure. I had a run up until last night but the server may not have been sending out new work units since it was more or less converged. But I will be putting up new runs later today or tomorrow so WU will start flowing soon.

Thanks for your patience!
Sidd

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Message 64770 - Posted: 29 Jun 2016, 14:01:33 UTC

I've been back for four of five days after a bit of an absence and had been recieving 1.60 during that time.

Anyway always nice to see a meaningful version bump.

Do these changes affact the actual science modelling or does it just improve the model througput validation/error ratio.


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