Date: Tue, 20 Jan 2015 09:58:00 +0000
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
(image/jpeg attachment: image003_jpg)