Re: IC files

From: Dimitry Ayzenberg <dayzenbe_at_andrew.cmu.edu>
Date: Mon, 14 Sep 2009 01:19:58 -0400

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
>>
>>
>>
>>
>>
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>>
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>
>
>
>
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-- 
Dimitry Ayzenberg
Carnegie Mellon University
Physics - Class of 2012
Cell:(732)-425-4534
Email: dayzenbe_at_andrew.cmu.edu
Received on 2009-09-14 07:20:00

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