Re: IC files

From: Dimitry Ayzenberg <dayzenbe_at_andrew.cmu.edu>
Date: Tue, 15 Sep 2009 21:05:11 -0400

I think I've pretty much got it under control. Thanks for the help. I just
had a couple of questions.

The blocks for the Iinitial condition file can be any size as long as the
block size before them contains what size they are? Or must they all be
the same, specific size? Or does just the header block have to be that
specific size, which is 256 bytes?

Also, does just doing an fprintf in C put the Initial Condition file in
the right format? It seems to read as if it's just a text file. Is there
anything special I need to add so that it prints out in the right format?

Thanks,
Dimitry

On Mon, September 14, 2009 08:44, Jay Billings wrote:
> If you have any problems, I can link you to some source code that should
> help you with the IO.
>
> Jay
>
>
> On Mon, Sep 14, 2009 at 8:25 AM, Dimitry Ayzenberg
> <dayzenbe_at_andrew.cmu.edu>wrote:
>
>
>>
>> I think I'll try that out. I can't seem to open it properly in Fortran.
>>
>>
>> Thanks,
>> Dimitry
>>
>>
>> On Mon, September 14, 2009 07:25, Jay Billings wrote:
>>
>>> Dimitry,
>>>
>>>
>>>
>>> It is also rather trivial to "invert" the read_snapshot.c file found
>>> in the "Analysis" directory. One benefit of doing it like this is that
>>> you have both read and write routines for Gadget2.
>>>
>>> Jay
>>>
>>>
>>>
>>> On Mon, Sep 14, 2009 at 1:19 AM, Dimitry Ayzenberg
>>> <dayzenbe_at_andrew.cmu.edu>wrote:
>>>
>>>
>>>
>>>>
>>>> Thank you very much. That helps a lot. I'm actually using Gadget to
>>>> try to do planet formation simulations, so I'll probably mess with
>>>> the initial conditions on my own. Just needed to know how to
>>>> actually access them.
>>>>
>>>> Dimitry
>>>>
>>>>
>>>>
>>>>
>>>> On Mon, September 14, 2009 01:10, Scott Wales wrote:
>>>>
>>>>
>>>>>
>>>>
>>>>> Hi Dimitry,
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Gadget initial condition files have the same format as snapshots.
>>>>> They
>>>>> are binary files, so you'll have to write a program to actually do
>>>>>
>>>> anything
>>>>> with them. The file format is detailed in the user's guide, but
>>>>> briefly the file consists of a series of blocks, each of which
>>>>> consist of an int containing the block size, a binary blob of data
>>>>> and then another int
>>>> with
>>>>> the block size. Fortran will read the blocks automatically with a
>>>>> unformatted read, for c use a function like
>>>>>
>>>>> #include <assert.h>
>>>>> #include <stdio.h>
>>>>> void ReadGadgetBlock(FILE* gadgetfile, void ** data, size_t *
>>>>> data_size){ unsigned int block_size; size_t number_read; // Get
>>>>> the size of the block number_read =
>>>>> fread(&block_size,1,sizeof(block_size),gadgetfile);
>>>>> assert(number_read == 1); // Allocate space for the data
>>>>> *data_size = block_size;
>>>>> *data = realloc(*data,*data_size);
>>>>> // Read the data
>>>>> number_read = fread(*data,*data_size,1,gadgetfile);
>>>>> assert(number_read ==
>>>>> *data_size);
>>>>> // Read the block footer
>>>>> number_read = fread(&block_size,1,sizeof(block_size),gadgetfile);
>>>>> assert(number_read == 1); assert(block_size == *data_size); }
>>>>>
>>>>>
>>>>> The contents of each block are detailed in the user's guide.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> The initial conditions you'll use depends on what you're
>>>>> simulating. For cosmological simulations try something like Edwin
>>>>> Sirko's ic
>>>>> (needs some format conversion) or Crocce et al.'s 2lpt. They will
>>>>> require input power spectra, found by something like cmbeasy or
>>>>> cmbfast.
>>>>>
>>>>> Cheers,
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> Scott Wales
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On 14/09/2009, at 2:40 PM, Dimitry Ayzenberg wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> Can someone please tell me how to open and read the .dat files
>>>>>> in the ICs folder? Also how to make initial condition files? I'm
>>>>>> a little confused about how to do either.
>>>>>>
>>>>>> Thanks,
>>>>>> Dimitry
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> -----------------------------------------------------------
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> If you wish to unsubscribe from this mailing, send mail to
>>>>>> minimalist_at_MPA-Garching.MPG.de with a subject of: unsubscribe
>>>>>> gadget-list A web-archive of this mailing list is available
>>>>>> here:
>>>>>> http://www.mpa-garching.mpg.de/gadget/gadget-list
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> -----------------------------------------------------------
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> If you wish to unsubscribe from this mailing, send mail to
>>>>> minimalist_at_MPA-Garching.MPG.de with a subject of: unsubscribe
>>>> gadget-list
>>>>> A web-archive of this mailing list is available here:
>>>>> http://www.mpa-garching.mpg.de/gadget/gadget-list
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Dimitry Ayzenberg
>>>> Carnegie Mellon University
>>>> Physics - Class of 2012
>>>> Cell:(732)-425-4534
>>>> Email: dayzenbe_at_andrew.cmu.edu
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> -----------------------------------------------------------
>>>>
>>>>
>>>>
>>>> If you wish to unsubscribe from this mailing, send mail to
>>>> minimalist_at_MPA-Garching.MPG.de with a subject of: unsubscribe
>>>> gadget-list A web-archive of this mailing list is available here:
>>>> http://www.mpa-garching.mpg.de/gadget/gadget-list
>>>>
>>>>
>>>>
>>>
>>
>>
>> --
>> Dimitry Ayzenberg
>> Carnegie Mellon University
>> Physics - Class of 2012
>> Cell:(732)-425-4534
>> Email: dayzenbe_at_andrew.cmu.edu
>>
>>
>>
>>
>>
>> -----------------------------------------------------------
>>
>>
>> If you wish to unsubscribe from this mailing, send mail to
>> minimalist_at_MPA-Garching.MPG.de with a subject of: unsubscribe
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>> http://www.mpa-garching.mpg.de/gadget/gadget-list
>>
>>
>


-- 
Dimitry Ayzenberg
Carnegie Mellon University
Physics - Class of 2012
Cell:(732)-425-4534
Email: dayzenbe_at_andrew.cmu.edu
Received on 2009-09-16 03:05:14

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