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From: Matthias Kühtreiber <a0749244_at_unet.univie.ac.at>

Date: Tue, 20 Jan 2015 11:52:04 +0100

Hi Phil,

Have you double-checked that the value of "SofteningGas" in your parameter

file is set to a non-zero value?

A gravitational softening of 0 can lead to similar errors you described

above.

Best wishes,

Matthias Kühtreiber

Department of Astrophysics

University of Vienna

On Di, 20.01.2015, 10:58, Phil Sutton wrote:

*> Hi all,
*

*>
*

*> For a while now I have been running a few simulations successfully using
*

*> non-gas particles. However, I now wish to include some gas particles and
*

*> have run into some problems getting Gadget2 to initial run. I now have two
*

*> initial conditions that creates a ring of particles around a larger
*

*> central mass. The velocities all assume circular Keplerian motions with
*

*> the following:
*

*> [cid:image003.jpg_at_01D03497.9310C440]
*

*>
*

*> All particle number densities, velocities and masses are the same (I added
*

*> in a new array for internal energies of gas particles). The only
*

*> difference is the particle type. The non-gas IC runs fine with no errors
*

*> and continues to evolve in a Keplerian way. However, when gas particles
*

*> are used for the ring a zero time step is assigned. I have tried altering
*

*> the smoothing lengths, mass, number of particles and scale of the system
*

*> from ridiculously small and large with no effect. The only thing that
*

*> allows Gadget2 to run is if I reduce the central mass down by a factor of
*

*> 10, which obviously results in the ring particles no longer having
*

*> Keplerian motions about the centre. I have probably made a simple error in
*

*> setting up of the initial conditions or an assumptions I’ve made when
*

*> using gas particles but am running out of ideas to try. Any help would be
*

*> great.
*

*>
*

*> Here is the errors for the gas particle IC followed by the successful
*

*> non-gas IC if it helps:
*

*>
*

*>
*

*> This is Gadget, version `2.0'.
*

*>
*

*>
*

*>
*

*> Running on 12 processors.
*

*>
*

*>
*

*>
*

*> Allocated 30 MByte communication buffer per processor.
*

*>
*

*>
*

*>
*

*> Communication buffer has room for 604946 particles in gravity computation
*

*>
*

*> Communication buffer has room for 245760 particles in density computation
*

*>
*

*> Communication buffer has room for 196608 particles in hydro computation
*

*>
*

*> Communication buffer has room for 196608 particles in domain
*

*> decomposition
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> Hubble (internal units) = 3.24078e-18
*

*>
*

*> G (internal units) = 6.672e-08
*

*>
*

*> UnitMass_in_g = 1
*

*>
*

*> UnitTime_in_s = 1
*

*>
*

*> UnitVelocity_in_cm_per_s = 1
*

*>
*

*> UnitDensity_in_cgs = 1
*

*>
*

*> UnitEnergy_in_cgs = 1
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> Allocated 0.567307 MByte for particle storage. 68
*

*>
*

*>
*

*>
*

*> Allocated 0.70079 MByte for storage of SPH data. 84
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> reading file `gas.dat' on task=0 (contains 35000 particles.)
*

*>
*

*> distributing this file to tasks 0-11
*

*>
*

*> Type 0 (gas): 34999 (tot= 0000034999) masstab=0
*

*>
*

*> Type 1 (halo): 0 (tot= 0000000000) masstab=0
*

*>
*

*> Type 2 (disk): 1 (tot= 0000000001) masstab=0
*

*>
*

*> Type 3 (bulge): 0 (tot= 0000000000) masstab=0
*

*>
*

*> Type 4 (stars): 0 (tot= 0000000000) masstab=0
*

*>
*

*> Type 5 (bndry): 0 (tot= 0000000000) masstab=0
*

*>
*

*>
*

*>
*

*> reading done.
*

*>
*

*> Total number of particles : 0000035000
*

*>
*

*>
*

*>
*

*> allocated 0.0762939 Mbyte for ngb search.
*

*>
*

*>
*

*>
*

*> Allocated 1.63065 MByte for BH-tree. 64
*

*>
*

*>
*

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 1436
*

*>
*

*> work-load balance=1.01143 memory-balance=1.01143
*

*>
*

*> exchange of 0000032087 particles
*

*>
*

*> domain decomposition done.
*

*>
*

*> begin Peano-Hilbert order...
*

*>
*

*> Peano-Hilbert done.
*

*>
*

*> Begin Ngb-tree construction.
*

*>
*

*> Ngb-Tree contruction finished
*

*>
*

*> ngb iteration 1: need to repeat for 0000034999 particles.
*

*>
*

*> ngb iteration 2: need to repeat for 0000034999 particles.
*

*>
*

*> ngb iteration 3: need to repeat for 0000034967 particles.
*

*>
*

*> ngb iteration 4: need to repeat for 0000034163 particles.
*

*>
*

*> ngb iteration 5: need to repeat for 0000027944 particles.
*

*>
*

*> ngb iteration 6: need to repeat for 0000014669 particles.
*

*>
*

*> ngb iteration 7: need to repeat for 0000004986 particles.
*

*>
*

*> ngb iteration 8: need to repeat for 0000001284 particles.
*

*>
*

*> ngb iteration 9: need to repeat for 0000000446 particles.
*

*>
*

*> ngb iteration 10: need to repeat for 0000000211 particles.
*

*>
*

*> ngb iteration 11: need to repeat for 0000000088 particles.
*

*>
*

*> ngb iteration 12: need to repeat for 0000000026 particles.
*

*>
*

*> ngb iteration 13: need to repeat for 0000000005 particles.
*

*>
*

*>
*

*>
*

*> Setting next time for snapshot file to Time_next= 0
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> writing snapshot file...
*

*>
*

*> done with snapshot.
*

*>
*

*>
*

*>
*

*> Setting next time for snapshot file to Time_next= 500
*

*>
*

*>
*

*>
*

*>
*

*>
*

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

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 1436
*

*>
*

*> work-load balance=1.01143 memory-balance=1.01143
*

*>
*

*> domain decomposition done.
*

*>
*

*> begin Peano-Hilbert order...
*

*>
*

*> Peano-Hilbert done.
*

*>
*

*> Start force computation...
*

*>
*

*> Tree construction.
*

*>
*

*> Tree construction done.
*

*>
*

*> Begin tree force.
*

*>
*

*> tree is done.
*

*>
*

*> Begin tree force.
*

*>
*

*> tree is done.
*

*>
*

*> Start density computation...
*

*>
*

*> Start hydro-force computation...
*

*>
*

*> force computation done.
*

*>
*

*>
*

*>
*

*> Error: A timestep of size zero was assigned on the integer timeline!
*

*>
*

*> We better stop.
*

*>
*

*> Task=0 Part-ID=0 dt=-nan tibase=3.72529e-05 ti_step=-2147483648 ac=-nan
*

*> xyz=(2.05361e+11|-1.32362e+09|0) tree=(-0.999847|0.006444340)
*

*>
*

*>
*

*>
*

*> hydro-frc=(-nan|-nan|-nan)
*

*>
*

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

*>
*

*>
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> Error: A timestep of size zero was assigned on the integer timeline!
*

*>
*

*> We better stop.
*

*>
*

*> Task=1 Part-ID=0 dt=-nan tibase=3.72529e-05 ti_step=-2147483648 ac=-nan
*

*> xyz=(1.40842e+11|-1.21532e+11|0) tree=(-0.922557|0.796070)
*

*>
*

*>
*

*>
*

*> hydro-frc=(-nan|-nan|-nan)
*

*> task 1: endrun called with an error level of 818
*

*>
*

*>
*

*>
*

*>
*

*> This is Gadget, version `2.0'.
*

*>
*

*>
*

*>
*

*> Running on 12 processors.
*

*>
*

*>
*

*>
*

*> Allocated 30 MByte communication buffer per processor.
*

*>
*

*>
*

*>
*

*> Communication buffer has room for 604946 particles in gravity computation
*

*>
*

*> Communication buffer has room for 245760 particles in density computation
*

*>
*

*> Communication buffer has room for 196608 particles in hydro computation
*

*>
*

*> Communication buffer has room for 196608 particles in domain
*

*> decomposition
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> Hubble (internal units) = 3.24078e-18
*

*>
*

*> G (internal units) = 6.672e-08
*

*>
*

*> UnitMass_in_g = 1
*

*>
*

*> UnitTime_in_s = 1
*

*>
*

*> UnitVelocity_in_cm_per_s = 1
*

*>
*

*> UnitDensity_in_cgs = 1
*

*>
*

*> UnitEnergy_in_cgs = 1
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> Allocated 0.53112 MByte for particle storage. 68
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> reading file `non_gas.dat' on task=0 (contains 32768 particles.)
*

*>
*

*> distributing this file to tasks 0-11
*

*>
*

*> Type 0 (gas): 0 (tot= 0000000000) masstab=0
*

*>
*

*> Type 1 (halo): 32767 (tot= 0000032767) masstab=0
*

*>
*

*> Type 2 (disk): 1 (tot= 0000000001) masstab=0
*

*>
*

*> Type 3 (bulge): 0 (tot= 0000000000) masstab=0
*

*>
*

*> Type 4 (stars): 0 (tot= 0000000000) masstab=0
*

*>
*

*> Type 5 (bndry): 0 (tot= 0000000000) masstab=0
*

*>
*

*>
*

*>
*

*> reading done.
*

*>
*

*> Total number of particles : 0000032768
*

*>
*

*>
*

*>
*

*> allocated 0.0762939 Mbyte for ngb search.
*

*>
*

*>
*

*>
*

*> Allocated 1.5753 MByte for BH-tree. 64
*

*>
*

*>
*

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 1450
*

*>
*

*> work-load balance=1.01807 memory-balance=1.01807
*

*>
*

*> exchange of 0000030112 particles
*

*>
*

*> domain decomposition done.
*

*>
*

*> begin Peano-Hilbert order...
*

*>
*

*> Peano-Hilbert done.
*

*>
*

*> Begin Ngb-tree construction.
*

*>
*

*> Ngb-Tree contruction finished
*

*>
*

*>
*

*>
*

*> Setting next time for snapshot file to Time_next= 0
*

*>
*

*>
*

*>
*

*>
*

*>
*

*> writing snapshot file...
*

*>
*

*> done with snapshot.
*

*>
*

*>
*

*>
*

*> Setting next time for snapshot file to Time_next= 500
*

*>
*

*>
*

*>
*

*>
*

*>
*

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

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 1450
*

*>
*

*> work-load balance=1.01807 memory-balance=1.01807
*

*>
*

*> domain decomposition done.
*

*>
*

*> begin Peano-Hilbert order...
*

*>
*

*> Peano-Hilbert done.
*

*>
*

*> Start force computation...
*

*>
*

*> Tree construction.
*

*>
*

*> Tree construction done.
*

*>
*

*> Begin tree force.
*

*>
*

*> tree is done.
*

*>
*

*> Begin tree force.
*

*>
*

*> tree is done.
*

*>
*

*> force computation done.
*

*>
*

*>
*

*>
*

*> Begin Step 1, Time: 4.88281, Systemstep: 4.88281
*

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 1450
*

*>
*

*> work-load balance=1.02153 memory-balance=1.38647
*

*>
*

*> exchange of 0000004772 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 2, Time: 9.76562, Systemstep: 4.88281
*

*>
*

*> domain decomposition...
*

*>
*

*> NTopleaves= 1457
*

*>
*

*> work-load balance=1.03279 memory-balance=1.36597
*

*>
*

*> exchange of 0000000226 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.
*

*>
*

*> Regards
*

*>
*

*> Phil Sutton
*

*> Physics Department
*

*> Loughborough University
*

*>
*

*>
*

Received on 2015-01-20 12:09:09

Date: Tue, 20 Jan 2015 11:52:04 +0100

Hi Phil,

Have you double-checked that the value of "SofteningGas" in your parameter

file is set to a non-zero value?

A gravitational softening of 0 can lead to similar errors you described

above.

Best wishes,

Matthias Kühtreiber

Department of Astrophysics

University of Vienna

On Di, 20.01.2015, 10:58, Phil Sutton wrote:

Received on 2015-01-20 12:09:09

*
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