Source code for MDAnalysis.topology.GSDParser

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"""GSD topology parser

.. versionadded:: 0.17.0

The :class:`GSDParser` generates a topology from HOOMD_ GSD topology/trajectory
files. The GSD file stores information on both the topology and the trajectory
in the same file, and allows for varying atom numbers/identities and topologies
during the course of the simulation. At the moment MDAnalysis can deal only
with the case in which there is no variation. The trajectory data are read with
the :class:`~MDAnalysis.coordinates.GSD.GSDReader` class.

.. _HOOMD:

To load a GSD HOOMD file::

   import MDAnalysis as mda
   u = mda.Universe("example.gsd")


.. autoclass:: GSDParser

from __future__ import absolute_import

import os
import gsd.hoomd
import numpy as np

from . import guessers
from .base import TopologyReaderBase
from ..core.topology import Topology
from ..core.topologyattrs import (

[docs]class GSDParser(TopologyReaderBase): """Parses a Hoomd GSD file to create a Topology Reads the following Attributes: - Atomtypes - Bonds - Angles - Dihedrals - Impropers - Radii - Masses The GSD file also stores a `body` property in the particles, and the parser uses this information to set the residue names and indices. NOTE: if the `body` index of any particle is negative, the parser will add an integer number (the absolute value of the minimum of all the body indices) to all the body indices. This is because MDAnalysis cannot handle negative residue indices. This means that in that case the residue index in the MDAnalysis.Universe will not correspond to the body index stored in the GSD file. """ format = 'GSD'
[docs] def parse(self, **kwargs): """Parse Hoomd GSD file .. versionadded:: 0.17.0 """ attrs = {} with,mode='rb') as t : # Here it is assumed that the particle data does not change in the # trajectory. snap = t[0] natoms = snap.particles.N ptypes = snap.particles.types atypes = [ptypes[idx] for idx in snap.particles.typeid] if len(atypes) != natoms: raise IOError("Number of types does not equal natoms.") attrs['types'] = Atomtypes(np.array(atypes, dtype=object)) # set radii, masses, charges p = snap.particles attrs['diameter'] = Radii(np.array(p.diameter / 2.,dtype=np.float32)) attrs['mass'] = Masses(np.array(p.mass,dtype=np.float64)) attrs['charge'] = Charges(np.array(p.charge,dtype=np.float32)) # set bonds, angles, dihedrals, impropers for attrname, attr, in ( ('bonds', Bonds), ('angles', Angles), ('dihedrals', Dihedrals), ('impropers', Impropers), ): try: val = getattr(snap,attrname) vals = [tuple(b_instance) for b_instance in] except: vals = [] attrs[attrname] = attr(vals) # get body ids to set residue number and ids blist = snap.particles.body.astype(np.int64) bodies = np.unique(blist).astype(np.int32) # this fixes the fact that the Topology constructor gets stuck in an # infinite loop if any resid is negative. if (blist<0).any() : m = blist.min() blist += abs(m) bodies = np.unique(blist).astype(np.int32) nbodies = bodies.size attrs = list(attrs.values()) attrs.append(Atomnames(np.array(atypes, dtype=object))) attrs.append(Atomids(np.arange(natoms) + 1)) attrs.append(Resids(bodies)) attrs.append(Resnums(bodies)) attrs.append(Resnames(bodies)) attrs.append(Segids(np.array(['SYSTEM'], dtype=object))) top = Topology(natoms, nbodies, 1, attrs=attrs, atom_resindex=blist) return top