Add tool for converting gadget3 ICs to EAGLE ICs in HDF format

tools/gadget3_to_eagleHDF.py

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+import numpy as np
+import os
+import argparse
+from scipy.io import FortranFile
+import h5py as h5
+
+"""
+Script for converting .gadget3 binary ICs to the hdf5 format, for use with the EAGLE code.
+
+Adapted from an IDL script by Rob Crain, by Jonathan Davies, 2021.
+
+Usage: ics2hdf.py ics_file
+* Creates an hdf5 file in the same directory as the original ICs, with the same name.
+"""
+
+def ics2hdf(ics_file):
+
+    raw_ics = os.path.abspath(ics_file)
+
+    # Do quick checks to make sure input is valid
+    assert os.path.isfile(raw_ics),'Input ICs file does not exist.'
+    assert raw_ics.split('.')[-1] == 'gadget3','Input ICs not valid. Please input GADGET3 binary ICs (.gadget3)'
+
+    out_ics = raw_ics[:-7] + 'hdf5'
+
+    print('Reading binary file '+raw_ics)
+
+    # Open the FORTRAN unformatted binary ICs
+    f = FortranFile(raw_ics, 'r')
+
+    # Read the header with the proper types
+    header = f.read_record('(6,)i4','(6,)f8','f8','f8','i4','i4','(6,)i4','i4','i4','f8','f8','f8','f8','i4','i4','(6,)i4','i4','i4','(56,)b')
+
+    hdict = {}
+    hdict['NumPart_ThisFile'] = header[0]
+    hdict['MassTable'] = header[1]
+    hdict['ExpansionFactor'] = header[2][0]
+    hdict['Time'] = header[2][0]
+    hdict['Redshift'] = header[3][0]
+    hdict['Flag_Sfr'] = header[4][0]
+    hdict['Flag_Feedback'] = header[5][0]
+    hdict['NumPart_Total'] = header[6]
+    hdict['Flag_Cooling'] = header[7][0]
+    hdict['NumFilesPerSnapshot'] = header[8][0]
+    hdict['BoxSize'] = header[9][0]
+    hdict['Omega0'] = header[10][0]
+    hdict['OmegaLambda'] = header[11][0]
+    hdict['HubbleParam'] = header[12][0]
+    hdict['Flag_StellarAge'] = header[13][0]
+    hdict['Flag_Metals'] = header[14][0]
+    hdict['NumPart_Total_HighWord'] = header[15]
+    hdict['Flag_DoublePrecision'] = header[17][0]
+
+    # Correction to header (from Rob Crain's original IDL script):
+    hdict['Flag_DoublePrecision'] = np.int32(0)
+
+    # Pointer to this dict element for later convenience
+    npart = hdict['NumPart_ThisFile']
+
+    # Get the particle array lengths
+    tot_npart = npart[1] + npart[2]
+
+    # Load the particles
+    pos = f.read_record('(%d,3)f4'%(tot_npart))
+    vel = f.read_record('(%d,3)f4'%(tot_npart))
+    ids = f.read_record('(%d,)i8'%(tot_npart))
+
+
+    # Write out the ICs in hdf5 format
+
+    print('Writing hdf5 file to '+out_ics)
+
+    out = h5.File(out_ics,'w')
+
+    print('Writing header...')
+
+    out_header = out.create_group('Header')
+
+    for key in hdict.keys():
+        out_header.attrs.create(key,data=hdict[key])
+
+    offset = 0
+    for ptype in range(len(npart)):
+
+        num = npart[ptype]
+        if num == 0:
+            continue
+
+        print('Writing PartType'+str(ptype)+'...')
+
+        out_pgroup = out.create_group('PartType%i'%(ptype))
+
+        out_pgroup.create_dataset('Coordinates',data=pos[offset:offset+num,:])
+        out_pgroup.create_dataset('Velocity',data=vel[offset:offset+num,:])
+        out_pgroup.create_dataset('ParticleIDs',data=ids[offset:offset+num])
+
+        offset += num
+
+    print('Done!')
+
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        'input_ICs',
+        type=str,
+        help="The input .gadget3 binary ICs file"
+    )
+    args = parser.parse_args()
+    ics2hdf(args.input_ICs)
+
+
+if __name__ == "__main__":
+    main()