[yt-users] Obtaining the current Enzo timestep from yt

trobolo dinni trobolo.trobolo.dinni5 at gmail.com
Mon Dec 2 16:14:46 PST 2013


Hi Sam,

referring to the Enzo documentation:

InitialTime (internal)The time, in code units, of the current step. For
cosmology the units are in free-fall times at the initial epoch (see *Enzo
Output Formats*<http://enzo.readthedocs.org/en/latest/user_guide/EnzoOutputFormat.html#enzooutputformats>).
Default: generally 0, depending on problemInitialdt (internal)The timestep,
in code units, for the current step. For cosmology the units are in
free-fall times at the initial epoch (see *Enzo Output
Formats*<http://enzo.readthedocs.org/en/latest/user_guide/EnzoOutputFormat.html#enzooutputformats>).
Default: generally 0, depending on problem
my understanding from this is that as Enzo does for the parameter
InitialTime, also Initialdt should be saved in the parameters file and
represents the TopGrid timestep computed by Enzo at each TopGrid cycle.So
when during a run the console outputs for example:
TopGrid dt = 7.815060e-05     time = 0.52042974743667    cycle = 7138

the time and cycle are actually saved in the parameter file (if an output
is scheduled for that cycle), but dt is not, while I would expect that to
be saved to.Am I right?
dt is the thing I need because I would like to do some data analysis that
requires the time step (iI need to analyse the evolution of some quantities
over a cycle).

Thanks,                Roberto


On 3 December 2013 10:43, Sam Skillman <samskillman at gmail.com> wrote:

> Hi Roberto,
>
> InitialTime is the current timestep in the simulation.  It refers to the
> start time of the current timestep (as opposed to an intermediate time
> during the adaptive timestepping in Enzo).  Initialdt is not written out to
> the output parameter files because it is only used for the very first step
> in the simulation.
>
> A shortcut that currently exists is pf.current_time, which is the same as
> pf.parameters['InitialTime'].
>
> I hope that helps,
> Sam
>
>
>
> On Mon, Dec 2, 2013 at 3:36 PM, trobolo dinni <
> trobolo.trobolo.dinni5 at gmail.com> wrote:
>
>> Hi Matt,
>>
>> yes, I don't know why it is not there.
>>
>> I tried with the pf.parameters function:
>>
>> *In [456]: pf.parameters['Initialdt']*
>>
>> *---------------------------------------------------------------------------*
>> *KeyError                                  Traceback (most recent call
>> last)*
>>
>> */home/cthulhu/Repository/Python/yt scripts/5.primary_damping_analysis.py
>> <http://5.primary_damping_analysis.py> in <module>()*
>> *----> 1 *
>> *      2 *
>> *      3 *
>> *      4 *
>> *      5 *
>>
>> *KeyError: 'Initialdt'*
>>
>>  *In [458]: pf.parameters['InitialTime']*
>> *Out[458]: 0.52818454582493*
>>
>> but since Initialdt is not there it is not able to find it.
>>
>> Can I ask if is there a way to tell Enzo to write out the Initialdt or
>> should be there by default?
>>
>> Thanks,
>>              Roberto
>>
>>
>>
>>
>>
>>
>> On 3 December 2013 10:13, Matthew Turk <matthewturk at gmail.com> wrote:
>>
>>> Hi Roberto,
>>>
>>> On Mon, Dec 2, 2013 at 6:10 PM, trobolo dinni
>>> <trobolo.trobolo.dinni5 at gmail.com> wrote:
>>> > Dear YT users,
>>> >
>>> > I would like to ask a simple question to which I was not able to find a
>>> > solution.
>>> >
>>> > My Enzo parameters file does not have any Initialdt line saved, also
>>> if by
>>> > reading the Enzo documentation at
>>> > http://enzo.readthedocs.org/en/latest/parameters/initialization.htmllooks
>>> > like the line should be there; and I would like to obtain the current
>>> > timestep from the output using yt.
>>> >
>>> > I would like to ask if is there a way to do that or if there is some
>>> > alternative solution.
>>> >
>>> > Thanks for the help,
>>> >                                  Roberto
>>>
>>> Weird that it's not there!  yt can get the cycle number if it's not.
>>> You can see this and other parameters by looking at pf.parameters .
>>> You can try using the "pprint" module to make it looks nice:
>>>
>>> import pprint
>>> pprint.pprint(pf.parameters)
>>>
>>> -Matt
>>>
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
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