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From: Volker Springel <volker_at_MPA-Garching.MPG.DE>

Date: Mon, 08 May 2006 17:07:31 +0200

Brad Krane wrote:

*> Hello,
*

*> I've been running the sample galaxy and after a while i get the following error:
*

*>
*

*> Begin Step 945, Time: 1.46332, Systemstep: 0.00152588
*

*> Start force computation...
*

*> Begin tree force.
*

*> tree is done.
*

*> force computation done.
*

*>
*

*> Begin Step 946, Time: 1.46484, Systemstep: 0.00152588
*

*> 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).
*

*> Particle Id=22724 on task=0 with coordinates (-2.06614|201.518|-4.22598) lies ou
*

*> tside PM mesh.
*

*> Stopping
*

*> In total 4 particles were outside allowed range.
*

*>
*

*> Allowed region for isolated PM mesh (coarse):
*

*> (-191.952|-181.732|-189.058) -> (191.743|201.963|194.637) ext=383.695 totmes
*

*> hsize=798.983 meshsize=3.12103
*

*>
*

*> Starting non-periodic PM calculation (grid=0).
*

*> Particle Id=37074 on task=0 with coordinates (-191.952|22.8454|7.37917) lies out
*

*> side PM mesh.
*

*> Stopping
*

*> In total 1 particles were outside allowed range.
*

*> task 0: endrun called with an error level of 68687
*

*>
*

*> What would cause this and how would I fix it? I suspect that I may
*

*> need to change a value in the galaxy.param file but looking over the
*

*> documentation I still don't know what might fix this.
*

*>
*

You need to set the compile-time parameter ENLARGEREGION to a value

larger than 1.0 (say 1.1 or 1.2) to solve this problem.

You are here using the PM method for a simulation of an isolated problem

with a changing spatial extension - this is possible, but typically not

a good idea. When a particle leaves the region covered by the PM mesh,

the code tries to place a new mesh by determining the maximum extension

of the particle distribution. When ENLARGEREGION is not declared

otherwise, a value of 1.0 is assumed, meaning that one particle will be

exactly on the boundary of the newly determined region. Depending on

floating point rounding, the code may then think that the particle is

already outside again, producing the above sequence of errors. However,

if ENLARGEREGION=1.1 is used, for example, the particle distribution may

extend by 10% before a new mesh needs to be found.

Note that examples for suitable makefiles for the galaxy problem are

also included in the code distribution, in the parameterfiles/

subdirectory, and this did not recommend the PM algorithm for this problem.

Volker

*> Thank you.
*

*>
*

*>
*

*> --
*

*> Brad
*

*>
*

*>
*

*>
*

*>
*

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

*>
*

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*

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*

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*

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*

Received on 2006-05-08 17:07:31

Date: Mon, 08 May 2006 17:07:31 +0200

Brad Krane wrote:

You need to set the compile-time parameter ENLARGEREGION to a value

larger than 1.0 (say 1.1 or 1.2) to solve this problem.

You are here using the PM method for a simulation of an isolated problem

with a changing spatial extension - this is possible, but typically not

a good idea. When a particle leaves the region covered by the PM mesh,

the code tries to place a new mesh by determining the maximum extension

of the particle distribution. When ENLARGEREGION is not declared

otherwise, a value of 1.0 is assumed, meaning that one particle will be

exactly on the boundary of the newly determined region. Depending on

floating point rounding, the code may then think that the particle is

already outside again, producing the above sequence of errors. However,

if ENLARGEREGION=1.1 is used, for example, the particle distribution may

extend by 10% before a new mesh needs to be found.

Note that examples for suitable makefiles for the galaxy problem are

also included in the code distribution, in the parameterfiles/

subdirectory, and this did not recommend the PM algorithm for this problem.

Volker

Received on 2006-05-08 17:07:31

*
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