"""Read and write Gromos87 (.GRO) file format."""
import datetime
import warnings
import numpy as np
import unyt as u
from unyt.array import allclose_units
from gmso.core.atom import Atom
from gmso.core.box import Box
from gmso.core.topology import Topology
from gmso.exceptions import NotYetImplementedWarning
[docs]def read_gro(filename):
"""Create a topology from a provided gro file.
The Gromos87 (gro) format is a common plain text structure file used
commonly with the GROMACS simulation engine. This file contains the
simulation box parameters, number of atoms, the residue and atom number for
each atom, as well as their positions and velocities (velocity is
optional). This method will receive a filepath representation either as a
string, or a file object and return a `topology`.
Parameters
----------
filename : str or file object
The path to the gro file either as a string, or a file object that
points to the gro file.
Returns
-------
gmso.core.topology
A `topology` object containing site information
Notes
-----
Gro files do not specify connections between atoms, the returned topology
will not have connections between sites either.
Currently this implementation does not support a gro file with more than 1
frame.
All residues and resid information from the gro file are currently lost
when converting to `topology`.
"""
top = Topology()
with open(filename, "r") as gro_file:
top.name = str(gro_file.readline().strip())
n_atoms = int(gro_file.readline())
coords = u.nm * np.zeros(shape=(n_atoms, 3))
for row, _ in enumerate(coords):
line = gro_file.readline()
if not line:
msg = (
"Incorrect number of lines in .gro file. Based on the "
"number in the second line of the file, {} rows of"
"atoms were expected, but at least one fewer was found."
)
raise ValueError(msg.format(n_atoms))
resid = int(line[:5])
res_name = line[5:10]
atom_name = line[10:15]
atom_id = int(line[15:20])
coords[row] = u.nm * np.array(
[
float(line[20:28]),
float(line[28:36]),
float(line[36:44]),
]
)
site = Atom(name=atom_name, position=coords[row])
top.add_site(site, update_types=False)
top.update_topology()
# Box information
line = gro_file.readline().split()
top.box = Box(u.nm * np.array([float(val) for val in line[:3]]))
# Verify we have read the last line by ensuring the next line in blank
line = gro_file.readline()
if line:
msg = (
"Incorrect number of lines in input file. Based on the "
"number in the second line of the file, {} rows of atoms "
"were expected, but at least one more was found."
)
raise ValueError(msg.format(n_atoms))
return top
[docs]def write_gro(top, filename):
"""Write a topology to a gro file.
The Gromos87 (gro) format is a common plain text structure file used
commonly with the GROMACS simulation engine. This file contains the
simulation box parameters, number of atoms, the residue and atom number for
each atom, as well as their positions and velocities (velocity is
optional). This method takes a topology object and a filepath string or
file object and saves a Gromos87 (gro) to disk.
Parameters
----------
top : gmso.core.topology
The `topology` to write out to the gro file.
filename : str or file object
The location and name of file to save to disk.
Notes
-----
Multiple residue assignment has not been added, each `site` will belong to
the same resid of 1 currently.
"""
top = _prepare_topology_to_gro(top)
with open(filename, "w") as out_file:
out_file.write(
"{} written by topology at {}\n".format(
top.name if top.name is not None else "",
str(datetime.datetime.now()),
)
)
out_file.write("{:d}\n".format(top.n_sites))
for idx, site in enumerate(top.sites):
warnings.warn(
"Residue information is not currently "
"stored or written to GRO files.",
NotYetImplementedWarning,
)
# TODO: assign residues
res_id = 1
res_name = "X"
atom_name = site.name
atom_id = idx + 1
out_file.write(
"{0:5d}{1:5s}{2:5s}{3:5d}{4:8.3f}{5:8.3f}{6:8.3f}\n".format(
res_id,
res_name,
atom_name,
atom_id,
site.position[0].in_units(u.nm).value,
site.position[1].in_units(u.nm).value,
site.position[2].in_units(u.nm).value,
)
)
if allclose_units(
top.box.angles,
u.degree * [90, 90, 90],
rtol=1e-5,
atol=0.1 * u.degree,
):
out_file.write(
" {:0.5f} {:0.5f} {:0.5f} \n".format(
top.box.lengths[0].in_units(u.nm).value.round(6),
top.box.lengths[1].in_units(u.nm).value.round(6),
top.box.lengths[2].in_units(u.nm).value.round(6),
)
)
else:
# TODO: Work around GROMACS's triclinic limitations #30
vectors = top.box.get_vectors()
out_file.write(
" {:0.5f} {:0.5f} {:0.5f} {:0.5f} {:0.5f} {:0.5f} {:0.5f} {:0.5f} {:0.5f} \n".format(
vectors[0, 0].in_units(u.nm).value.round(6),
vectors[1, 1].in_units(u.nm).value.round(6),
vectors[2, 2].in_units(u.nm).value.round(6),
vectors[0, 1].in_units(u.nm).value.round(6),
vectors[0, 2].in_units(u.nm).value.round(6),
vectors[1, 0].in_units(u.nm).value.round(6),
vectors[1, 2].in_units(u.nm).value.round(6),
vectors[2, 0].in_units(u.nm).value.round(6),
vectors[2, 1].in_units(u.nm).value.round(6),
)
)
def _prepare_topology_to_gro(top):
"""Modify topology, as necessary, to fit limitations of the GRO format."""
if np.min(top.positions) < 0:
warnings.warn(
"Topology contains some negative positions. Translating "
"in order to ensure all coordinates are non-negative."
)
return top