Re: Run-time error: A timestep of size zero was assigned

From: Christopher Erick Moody <>
Date: Fri, 16 Nov 2007 16:19:20 -0800


    I am running a fairly simple simulation of 1500 particles in an
NFW profile. I have a similar error: 'A timestep of size zero was
assigned on the integer timeline!' that always occurs on the first
timestep. It was suggested that the particle in question (1495) is an
outlier and may cause problem. But if I remove it, the error simply
moves to another particle (1348). Removing that particle means that
particle 1493, and then particle 1492 have errors. None of these
particles are outliers, and are relatively close to other particles,
so I'm not sure why GADGET-2 would have problems with them to begin

Any help is appreciated,

(the error is copied below:)

Begin Step 0, Time: 0, Systemstep: 0
domain decomposition...
NTopleaves= 162
work-load balance=1 memory-balance=1
domain decomposition done.
begin Peano-Hilbert order...
Peano-Hilbert done.
Start force computation...
Starting non-periodic PM calculation (grid=0).
done PM.
Tree construction.
Tree construction done.
Begin tree force.
tree is done.
Begin tree force.
tree is done.
force computation done.

Error: A timestep of size zero was assigned on the integer timeline!
We better stop.
Task=0 Part-ID=1495 dt=nan tibase=1.86265e-09 ti_step=-2147483648
ac=nan xyz=(-2507.5|-1560.8|-253.42) tree=(nan|nannan)

task 0: endrun called with an error level of 818
task 0: endrun called with an error level of 818

From: Hugo Vicente Capelato <>
Date: Tue, 13 Jun 2006 09:52:02 -0300


Im sorry, I didnt had time yet to regard what is happening in detail
with my simulations and give you a more elaborated answer. Im terribly
busy these times. Anyway, from past simulations for which I encountered
the same error messages, I think Im having some particles escaping to very
large distances, as suggested by Ives, and that is the cause of my troubles.

To fix this, I think you must remove these particles by hand and then reestart
the simulation ...

Cheers, H.

Quoting Yago Ascasibar <>:

> Hi,
> I've also had such a problem, and I never really understood why. Actually,
> it
> seems likely that I do have some isolated particles near the boundaries.
> Could you please elaborate a little bit more on what may be happening?
> Thanks a lot,
> Yago
> On Saturday 10 June 2006 12:18, Yves Revaz wrote:
> > 2) Check that the snapshot from which you re-start the simulation do not
> > contains Nan or Inf numbers, or isolated particles at very large
> > distance from the
> > center of mass or very large velocities.
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Received on 2007-11-17 01:19:22

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