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From: Nathan Goldbaum <nathan12343_at_gmail.com>

Date: Mon, 31 Oct 2016 20:38:21 -0500

On Mon, Oct 31, 2016 at 8:26 PM, Raymond Carlberg <

raymond.carlberg_at_utoronto.ca> wrote:

*> I have set the minimum time step to a value below what the dynamic range
*

*> should reasonably need. Indeed all is well for about ½ of the longest
*

*> dynamical time. The time step does not shrink to zero, it just drops in one
*

*> step.
*

*>
*

I'd trace through the code to figure out exactly where this is happening. I

usually do this using printf's or GDB.

It sounds vaguely like integer or floating point overflow, but that's just

a vague guess on my part.

*>
*

*>
*

*> *From:* isbug01_at_gmail.com [mailto:isbug01_at_gmail.com] *On Behalf Of *ISAAC
*

*> SHLOSMAN
*

*> *Sent:* Monday, October 31, 2016 9:09 PM
*

*> *To:* Gadget General Discussion <gadget-list_at_MPA-Garching.MPG.DE>
*

*> *Subject:* Re: [gadget-list] RE: Re: Gadget stalling without apparent
*

*> reason
*

*>
*

*>
*

*>
*

*> Hi Raymond,
*

*> This because your extreme dynamic range and a finite number of time bins
*

*> results in dt going to 0. Find a way to decrease dynamic range
*

*>
*

*> Isaac
*

*>
*

*>
*

*>
*

*> On Oct 31, 2016 7:45 PM, "Raymond Carlberg" <raymond.carlberg_at_utoronto.ca>
*

*> wrote:
*

*>
*

*> HI – I am running Gadget2 on a 32 node machine. Works well for more than
*

*> 10,000 steps, then dt goes to zero with no complaints from the program so
*

*> the run continues for some time with no progress. DONOTSTOP is not
*

*> implemented. Softenings are good. TreeAllocFactor boosted, etc, but no go .
*

*> The gravity calculation has extreme density ranges.
*

*>
*

*> --Ray
*

*>
*

*>
*

*>
*

*> Restarting shows a possible problem (Nf=0 below):
*

*>
*

*> Step= 9 t= 1.55115 dt= 0.000128937
*

*>
*

*> Nf= 0000064647 total-Nf= 0001622692 ex-frac= 21.9985 iter= 1
*

*>
*

*> work-load balance: 18.532 max=4.10968 avg=0.221762 PE0=1.98117
*

*>
*

*> particle-load balance: 4.77931
*

*>
*

*> max. nodes: 37131, filled: 0.0066013
*

*>
*

*> part/sec=4554.93 | 245.788 ia/part=5650.51 (0)
*

*>
*

*>
*

*>
*

*> Step= 10 t= 1.55115 dt= 0
*

*>
*

*> Nf= 0000000000 total-Nf= 0001622692 ex-frac= -nan iter= 0
*

*>
*

*> work-load balance: -nan max=0 avg=0 PE0=0
*

*>
*

*> particle-load balance: 4.77931
*

*>
*

*> max. nodes: 37131, filled: 0.0066013
*

*>
*

*> part/sec=0 | -nan ia/part=-nan (-nan)
*

*>
*

*>
*

*>
*

*> ^^^^^^^^^^^^^^^^^^^and the output at the time of the problem.
*

*>
*

*>
*

*>
*

*> Begin Step 13838, Time: 1.55121, Systemstep: 0.000152588
*

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 4124
*

*>
*

*> work-load balance=36.5349 memory-balance=4.45177
*

*>
*

*> exchange of 0000288372 particles
*

*>
*

*> domain decomposition done.
*

*>
*

*> begin Peano-Hilbert order...
*

*>
*

*> Peano-Hilbert done.
*

*>
*

*> Start force computation...
*

*>
*

*> Tree construction.
*

*>
*

*> Tree construction done.
*

*>
*

*> Begin tree force.
*

*>
*

*> tree is done.
*

*>
*

*> force computation done.
*

*>
*

*>
*

*>
*

*> Begin Step 13839, Time: 1.55121, Systemstep: 0
*

*>
*

*> Start force computation...
*

*>
*

*> Begin tree force.
*

*>
*

*> tree is done.
*

*>
*

*> force computation done.
*

*>
*

*>
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> -----------------------------------------------------------
*

*>
*

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*

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*

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*

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*

*>
*

*>
*

*>
*

*> -----------------------------------------------------------
*

*>
*

*> If you wish to unsubscribe from this mailing, send mail to
*

*> minimalist_at_MPA-Garching.MPG.de with a subject of: unsubscribe gadget-list
*

*> A web-archive of this mailing list is available here:
*

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*

*>
*

*>
*

Received on 2016-11-01 02:38:44

Date: Mon, 31 Oct 2016 20:38:21 -0500

On Mon, Oct 31, 2016 at 8:26 PM, Raymond Carlberg <

raymond.carlberg_at_utoronto.ca> wrote:

I'd trace through the code to figure out exactly where this is happening. I

usually do this using printf's or GDB.

It sounds vaguely like integer or floating point overflow, but that's just

a vague guess on my part.

Received on 2016-11-01 02:38:44

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