garnett¶

Installation¶

Requirements¶

Installing the garnett package requires Python 3.5+, numpy, and rowan.

Note

If you need high performance when reading DCD files, please install Cython and build the package from source. Packages distributed via conda or pip wheels contain only the pure Python DCD reader.

With conda¶

To install the package with conda, execute

$ conda install -c conda-forge garnett

To upgrade, execute

$ conda update garnett

Note

This is the recommended installation method.

With pip¶

To install the package with the package manager pip, execute

$ pip install garnett --user

To upgrade the package, simply execute the same command with the –upgrade option.

$ pip install garnett --user --upgrade

From source¶

To install from source, you can clone the git repository and use the setup.py to install the package. If Cython is installed, the DCD reader extension will be built with Cython for improved performance.

git clone https://github.com/glotzerlab/garnett.git
cd garnett
python setup.py install --user

Quickstart¶

Reading and writing of trajectories¶

Reading and writing with automatic filetype detection¶

The garnett.read() and garnett.write() functions will automatically determine the type of a trajectory from its file extension. This can be used to quickly load and save Trajectory objects.

import garnett
# Load a GSD file...
with garnett.read('dump.gsd') as traj:
    print(len(traj))
    # ...do things with the trajectory, then output a GTAR file
    garnett.write(traj, 'output.tar')

Using reader and writer classes¶

Readers and writers are defined in the reader and writer modules. The following code uses the PosFileReader and PosFileWriter as an example.

from garnett.reader import PosFileReader
from garnett.writer import PosFileWriter

pos_reader = PosFileReader()
pos_writer = PosFileWriter()

with open('posfile.pos') as file:
    # Access the trajectory
    traj = pos_reader.read(file)

    # Write to standard out:
    pos_writer.write(traj)

    # or directly to a file:
    with open('out.pos', 'w') as posfile:
        pos_writer.write(traj, posfile)

Data access¶

Indexing and slicing¶

Once you read a trajectory, access individual frames or sub-trajectories by indexing and slicing:

# Select individual frames:
first_frame = traj[0]
last_frame = traj[-1]
n_th_frame = traj[n]
# and so on

# Create a sub-trajectory from the ith frame
# to the (j-1)th frame:
sub_trajectory = traj[i:j]

# We can use advanced slicing techniques:
every_second_frame = traj[::2]
the_last_ten_frames = traj[-10::]

The actual trajectory data is then either accessed on a per trajectory or per frame basis.

Trajectory array access¶

The complete trajectory may be loaded into memory by calling the load_arrays() method. This will allow access to fields such as position, orientation, and velocity across all frames and particles. Supported properties are listed below:

traj.load_arrays()
traj.box             # M
traj.N               # M
traj.types           # MxT
traj.type_shapes     # MxT
traj.typeid          # MxN
traj.position        # MxNx3
traj.orientation     # MxNx4
traj.velocity        # MxNx3
traj.mass            # MxN
traj.charge          # MxN
traj.diameter        # MxN
traj.moment_inertia  # MxNx3
traj.angmom          # MxNx4
traj.image           # MxNx3

# M is the number of frames
# T is the number of particle types in a frame
# N is the number of particles in a frame

Individual frame access¶

Individual frames can be accessed via indexing a (sub-)trajectory object:

frame = traj[i]
frame.box              # garnett.trajectory.Box object
frame.N                # scalar, number of particles
frame.types            # T, string names for each type
frame.type_shapes      # T, list of shapes for each type
frame.typeid           # N, type indices of each particle
frame.position         # Nx3
frame.orientation      # Nx4
frame.velocity         # Nx3
frame.mass             # N
frame.charge           # N
frame.diameter         # N
frame.moment_inertia   # Nx3
frame.angmom           # Nx4
frame.image            # Nx3
frame.data             # Dictionary of lists for each attribute
frame.data_key         # List of strings

Iterating over trajectories¶

Iterating over trajectories is the most memory-efficient form of data access. Each frame will be loaded prior to access and unloaded post access, such that there is only one frame loaded into memory at the same time.

# Iterate over a trajectory directly for read-only data access
for frame in traj:
    print(frame.position)

Efficient modification of trajectories¶

Use a combination of reading, writing, and iteration for memory-efficient modification of large trajectory data. This is an example on how to modify frames in-place:

import numpy as np
import garnett

def center(frame):
    frame.position -= np.average(frame.position, axis=0)
    return frame

with garnett.read('in.pos') as traj:
    traj_centered = Trajectory((center(frame) for frame in traj))
    garnett.write(traj_centered, 'out.pos')

Loading trajectories into memory¶

The Trajectory class is designed to be memory-efficient. This means that loading all trajectory data into memory requires an explicit call of the load() or load_arrays() methods.

# Make trajectory data accessible via arrays:
traj.load_arrays()
traj.position

# Load all frames:
traj.load()
frame = traj[i]
traj.position    # load() also loads arrays

Note

In general, loading all frames with load() is more expensive than just loading arrays with load_arrays(). Loading all frames also loads the arrays.

Sub-trajectories inherit already loaded data:

traj.load_arrays()
sub_traj = traj[i:j]
sub_traj.position

Tip

If you are only interested in sub-trajectory data, consider to call load() or load_arrays() only for the sub-trajectory.

Example use with HOOMD-blue¶

The garnett frames can be used to initialize HOOMD-blue simulations by creating snapshots or copying the frame data to existing snapshots with the to_hoomd_snapshot() method:

import garnett
import hoomd

with garnett.read('cube.pos') as traj:

    # Initialize from last frame
    snapshot = traj[-1].to_hoomd_snapshot()
    system = hoomd.init.read_snapshot(snapshot)

    # Restore last frame
    snapshot = system.take_snapshot()
    traj[-1].to_hoomd_snapshot(snapshot)

Readers & Writers¶

This is the API documentation for all readers and writers provided by garnett.

Automatic reader/writer¶

garnett.read(filename_or_fileobj, template=None, fmt=None)[source]¶

This function reads a file and returns a trajectory, autodetecting the file format unless fmt is specified.

Parameters:	filename_or_fileobj (string or file object) – Filename to read. template (string) – Optional template for the GSDHOOMDFileReader. fmt (string) – File format, one of ‘gsd’, ‘gtar’, ‘pos’, ‘cif’, ‘dcd’, ‘xml’ (default: None, autodetected from filename_or_fileobj)
Returns:	Trajectory read from the file.
Return type:	`Trajectory`

garnett.write(traj, filename_or_fileobj, fmt=None)[source]¶

This function writes a trajectory to a file, autodetecting the file format unless fmt is specified.

Parameters:	traj (`Trajectory`) – Trajectory to write. filename_or_fileobj (string or file object) – Filename to write. fmt (string) – File format, one of ‘gsd’, ‘gtar’, ‘pos’, ‘cif’ (default: None, autodetected from filename_or_fileobj)

General API¶

Readers and writers are defined in the reader and writer modules. All readers and writers work with file-like objects and use the following API:

reader = garnett.reader.Reader()
writer = garnett.writer.Writer()

with open('trajectory_file') as infile:
    traj = reader.read(infile)

    # Dump to a string:
    pos = writer.dump(traj)

    # Write to standard out:
    writer.write(traj)

    # or directly to a file:
    with open('dump', 'w') as outfile:
        writer.write(traj, outfile)

Important

Some readers and writers work with binary files, which means that when opening those files for reading or writing you need to use the rb or wb mode. This applies for example to DCD-files:

dcd_reader = garnett.reader.DCDFileReader()
with open('dump.dcd', 'rb') as dcdfile:
    dcd_traj = dcd_reader.read(dcdfile)

File Formats¶

This table outlines the supported properties of each format reader and writer.

Format	Position	Box	Orientation	Velocity	Shape	Additional Properties (See below)
POS	RW	RW	RW	N/A+	RW	N/A
GSD	RW	RW	RW	RW	RW	RW
GTAR	RW	RW	RW	RW	RW	RW
CIF	RW	RW	N/A	N/A	N/A	N/A
DCD	R	R	R	R	N/A	N/A
XML	R	R	R	R	N/A	N/A

RW indicates garnett can read and write on this format.
R indicates garnett can only read.
N/A indicates the format does not support storing this property.
Additional Properties:
- Mass
- Charge
- Diameter
- Angular momentum
- Moment of inertia
- Image

The following collection of readers and writers is ordered by different file formats.

POS Files¶

The POS format is a non-standardized text-based format which is human-readable, but very inefficient for storing of trajectory data. The format is used as primary input/output format for the injavis visualization tool. HOOMD-blue provides a writer for this format, which is classified as deprecated since version 2.0.

class garnett.reader.PosFileReader(precision=None)[source]¶

POS-file reader for the Glotzer Group, University of Michigan.

Authors: Carl Simon Adorf, Richmond Newmann

reader = PosFileReader()
with open('a_posfile.pos', 'r', encoding='utf-8') as posfile:
    return reader.read(posfile)

Parameters:	precision (int) – The number of digits to round floating-point values to.

read(stream, default_type='A')[source]¶

Read text stream and return a trajectory instance.

Parameters:	stream (A file-like textstream.) – The stream, which contains the posfile. default_type (str) – The default particle type for posfile dialects without type definition.

class garnett.writer.PosFileWriter(rotate=False)[source]¶

POS-file writer for the Glotzer Group, University of Michigan.

Author: Carl Simon Adorf

writer = PosFileWriter()
with open('a_posfile.pos', 'w', encoding='utf-8') as posfile:
    writer.write(trajectory, posfile)

Parameters:	rotate (bool) – Rotate the system into the view rotation instead of adding it to the metadata with the ‘rotation’ keyword.

dump(trajectory)[source]¶

Serialize trajectory into pos-format.

Parameters:	trajectory (`Trajectory`) – The trajectory to serialize.
Return type:	str

write(trajectory, file=<_io.TextIOWrapper name='<stdout>' mode='w' encoding='UTF-8'>)[source]¶

Serialize a trajectory into pos-format and write it to file.

Parameters:	trajectory (`Trajectory`) – The trajectory to serialize file – A file-like object.

GSD (HOOMD-blue schema)¶

The GSD format is a highly efficient and versatile binary format for storing and reading trajectory data. HOOMD-blue provides a writer for this format.

GeTAR¶

The GeTAR format is a highly versatile, binary format for storing and reading trajectory data. HOOMD-blue provides a writer for this format.

class garnett.reader.GetarFileReader[source]¶

getar-file reader for the Glotzer Group, University of Michigan.

Authors: Matthew Spellings, Carl Simon Adorf

Read GEneric Trajectory ARchive files, a binary format designed for efficient, extensible storage of trajectory data.

This class provides a wrapper for the gtar library.

reader = GetarFileReader()
with open('trajectory.tar', 'rb') as file:
    traj = reader.read(file)

read(stream, default_type='A', default_box=None)[source]¶

Read binary stream and return a trajectory instance.

Parameters:	stream (A file-like binary stream.) – The stream, which contains the GeTarFile. default_type (str) – The default particle type for posfile dialects without type definition. default_box (`numpy.ndarray`) – The default_box value is used if no box is specified in the libgetar file. Defaults to [Lx=Ly=Lz=1.0].

HOOMD-blue XML¶

The HOOMD-blue XML format contains topological information about one individual frame. HOOMD-blue provides a writer for this format, which is classified as deprecated since version 2.0.

class garnett.reader.HOOMDXMLFileReader[source]¶

Reader for XML-files containing HOOMD-blue snapshots.

read(stream)[source]¶

Read text stream and return a trajectory instance.

Parameters:	stream (A file-like textstream.) – The stream, which contains the xmlfile.

DCD¶

The DCD format is a very storage efficient binary format for storing simple trajectory data. The format contains only data about particle positions and the simulation boxes of individual frames.

HOOMD-blue provides a writer for this format with a special dialect for 2-dimensional systems. The garnett DCD reader is capable of reading both the standard and the 2-dim. dialect.

Note

Unlike most other readers, the DCDFileReader will return an instance of DCDTrajectory, which is optimized for the DCD-format. This special trajectory class provides the xyz() method for accessing xyz-coordinates with minimal overhead.

class garnett.reader.DCDFileReader[source]¶

DCD-file reader for the Glotzer Group, University of Michigan.

Author: Carl Simon Adorf

A dcd file consists only of positions. To provide additional information it is possible to provide a frame object, whose properties are copied into each frame of the dcd trajectory.

The example is given for a HOOMD-blue xml frame:

xml_reader = HOOMDXMLFileReader()
dcd_reader = DCDFileReader()

with open('init.xml') as xmlfile:
    with open('dump.dcd', 'rb') as dcdfile:
        xml_frame = xml_reader.read(xmlfile)[0]
        traj = reader.read(dcdfile, xml_frame)

Note

If the topology frame is 2-dimensional, the dcd trajectory positions are interpreted such that the first two values contain the xy-coordinates, the third value is an euler angle.

The euler angle is converted to a quaternion and stored in the orientation of the frame.

To retrieve the euler angles, simply convert the quaternion:

alpha = 2 * np.arccos(traj[0].orientations.T[0])

read(stream, frame=None, default_type=None)¶

Read binary stream and return a trajectory instance.

Parameters:	stream (A file-like binary stream) – The stream, which contains the dcd-file. frame (`trajectory.Frame`) – A frame containing topological information that cannot be encoded in the dcd-format. default_type (str) – A type name to be used when no first frame is provided, defaults to ‘A’.
Returns:	A trajectory instance.
Return type:	`DCDTrajectory`

class garnett.dcdfilereader.DCDTrajectory(frames=None, dtype=None)[source]¶

arrays_loaded()[source]¶

Returns true if arrays are loaded into memory.

CIF¶

The Crystallographic Information File (CIF) format is a text-based format primarily used in the context of crystallography.

class garnett.reader.CifFileReader(precision=None, tolerance=0.001)[source]¶

CIF-file reader for the Glotzer Group, University of Michigan.

Requires the PyCifRW package to parse CIF files.

Authors: Matthew Spellings

reader = CifFileReader()
with open('a_ciffile.cif', 'r') as ciffile:
    traj = reader.read(ciffile)

Parameters:	precision (int) – The number of digits to round floating-point values to. tolerance (float) – Floating-point tolerance (in fractional coordinates) of particle identity as symmetry operations are applied.

read(stream, default_type='A')[source]¶

Read text stream and return a trajectory instance.

Parameters:	stream (A file-like textstream.) – The stream, which contains the ciffile. default_type (str) – The default particle type for ciffile dialects without type definition.

class garnett.writer.CifFileWriter[source]¶

cif-file writer for the Glotzer Group, University of Michigan.

Authors: Julia Dshemuchadse, Carl Simon Adorf

writer = CifFileWriter()

# write to screen:
write.write(trajectory)

# write to file:
with open('a_ciffile.pos', 'w') as ciffile:
    writer.write(trajectory, ciffile)

dump(trajectory, data='simulation', occupancy=None, fractional=False, raw=False)[source]¶

Serialize trajectory into cif-format.

Parameters:	trajectory (`Trajectory`) – The trajectory to serialize. data (str) – Identifier which be will written to the file, signifying the origin of the data. occupancy (numpy.array) – The default occupancy of individual particles.
Return type:	str

write(trajectory, file=<_io.TextIOWrapper name='<stdout>' mode='w' encoding='UTF-8'>, data='simulation', occupancy=None, fractional=False, raw=False)[source]¶

Serialize a trajectory into cif-format and write it to file.

Parameters:

trajectory (Trajectory) – The trajectory to serialize
file (A file-like object.) – The file to write the trajectory to.
data (str) – Identifier which be will written to the file, signifying the origin of the data.
occupancy (int) – The default occupancy of individual particles.
fractional (bool) – Whether or not the input coordinates are fractional
raw (bool) – Whether or not to write the raw CIF coordinates (with no transformations)

Trajectory API¶

Instances of Trajectory give access to trajectory data stored in files and file-like objects. In the simplest case, trajectories are just a sequence of Frame instances.

Trajectories¶

class garnett.trajectory.Trajectory(frames=None, dtype=None)[source]¶

Manages a particle trajectory data resource.

A trajectory is basically a sequence of Frame instances.

Trajectory data can either be accessed as coherent NumPy arrays:

traj.load_arrays()
M = len(traj)
traj.N             # M
traj.position      # MxNx3
traj.orientation   # MxNx4
traj.typeid        # MxN

or by individual frames:

first_frame = traj[0]
last_frame = traj[-1]
n_th_frame = traj[n]

first_frame.position      # Nx3
first_frame.orientation   # Nx4
first_frame.types         # Nx1

You can iterate through individual frames:

for frame in trajectory:
    print(frame.position)

and create a sub-trajectory from the i’th to the (j-1)’th frame:

sub_trajectory = traj[i:j]

Parameters:	frames (`Frame`) – The individual frames of this trajectory. dtype – The default data type for trajectory data.

N¶

Access the frame sizes as a NumPy array.

Mostly important when the trajectory has varying size.

pos_i = traj.position[i][0:traj.N[i]]

Returns:	frame sizes as array with length M
Return type:	`numpy.ndarray` (dtype= `numpy.int_`)
Raises:	RuntimeError – When accessed before calling `load_arrays()` or `load()`.

angmom¶

Access the particle angular momenta as a NumPy array.

Returns:	particle angular momenta quaternions as (Nx4) element array
Return type:	`numpy.ndarray`
Raises:	RuntimeError – When accessed before calling `load_arrays()` or `load()`.

arrays_loaded()[source]¶

Returns true if arrays are loaded into memory.

Frames¶

Trajectory data can be accessed via individual frames.

class garnett.trajectory.Frame(dtype=None)[source]¶

A frame is a container object for the actual frame data.

The frame data is read from the origin stream whenever accessed.

Parameters:	dtype – The data type for frame data.

N¶: Number of particles.

angmom¶: Nx4 array of angular momenta for N particles represented as quaternions.

box¶: Instance of Box

charge¶: Nx1 array of charges for N particles.

copyto_snapshot(snapshot)[source]¶: Copy this frame to a HOOMD-blue snapshot.

Deprecated since version 0.7.0: This will be removed in 0.8.0. Use to_hoomd_snapshot.

data¶: A dictionary of lists for each attribute.

data_keys¶: A list of strings, where each string represents one attribute.

diameter¶: Nx1 array of diameters for N particles.

dtype¶: Return the data type for frame data.

classmethod from_hoomd_snapshot(snapshot)[source]¶

Constructs a Frame object from a HOOMD-blue snapshot.

Parameters:	snapshot – A HOOMD snapshot.

image¶: Nx3 array of periodic images for N particles in 3 dimensions.

load()[source]¶: Load the frame into memory.

loaded()[source]¶: Returns True if the frame is loaded into memory.

make_snapshot()[source]¶: Create a HOOMD-blue snapshot object from this frame.

Deprecated since version 0.7.0: This will be removed in 0.8.0. Use to_hoomd_snapshot with no argument.

mass¶: Nx1 array of masses for N particles.

moment_inertia¶: Nx3 array of principal moments of inertia for N particles in 3 dimensions.

orientation¶: Nx4 array of rotational coordinates for N particles represented as quaternions.

orientations¶: Nx4 array of rotational coordinates for N particles represented as quaternions. Deprecated alias for orientation.

Deprecated since version 0.7.0: This will be removed in 0.8.0. This property is deprecated, use orientation instead.

position¶: Nx3 array of coordinates for N particles in 3 dimensions.

positions¶: Nx3 array of coordinates for N particles in 3 dimensions. Deprecated alias for position.

Deprecated since version 0.7.0: This will be removed in 0.8.0. This property is deprecated, use position instead.

shapedef¶: An ordered dictionary of instances of Shape.

Deprecated since version 0.7.0: This will be removed in 0.8.0. This property is deprecated, use type_shapes instead. Until its removal, shapedef keys should not be individually set, only the entire dictionary at once.

to_hoomd_snapshot(snapshot=None)[source]¶: Copy this frame to a HOOMD-blue snapshot.

to_plato_scene(backend, scene=None)[source]¶

Create a plato scene from this frame.

Parameters:	backend (str) – Backend name to use with plato. The backend must support all primitives corresponding to shapes defined in this frame. scene (`plato.draw.Scene`) – Scene object to render into. By default, a new scene is created.

type_shapes¶: T list of shape definitions.

typeid¶: N array of type indices for N particles.

types¶: T array of type names represented as strings.

unload()[source]¶

Unload the frame from memory.

Use this method carefully. This method removes the frame reference to the frame data, however any other references that may still exist, will prevent a removal of said data from memory.

velocities¶: Nx3 array of velocities for N particles in 3 dimensions. Deprecated alias for velocity.

Deprecated since version 0.7.0: This will be removed in 0.8.0. This property is deprecated, use velocity instead.

velocity¶: Nx3 array of velocities for N particles in 3 dimensions.

view_rotation¶: A quaternion specifying a rotation that should be applied for visualization.

Box¶

The box instance gives access to the box of individual frames.

class garnett.trajectory.Box(Lx, Ly, Lz, xy=0.0, xz=0.0, yz=0.0, dimensions=3)[source]¶

A triclinic box class.

You can access the box size and tilt factors via attributes:

# Reading
length_x = box.Lx
tilt_xy = box.xy
# etc.

# Setting
box.Lx = 10.0
box.Ly = box.Lz = 5.0
box.xy = box.xz = box.yz = 0.01
# etc.

Shape Definitions¶

Shape definitions contain information about the shape of individual particles. Some shapes define a type_shape property, which returns a dict for consumption by visualization tools. The type_shape specification can be found here: Shape Visualization.

class garnett.shapes.FallbackShape[source]¶

This shape definition class is used when no specialized Shape class can be applied.

The fallback shape definition is a string containing the definition.

class garnett.shapes.Shape(shape_class=None, color=None)[source]¶

Parent class of all shape objects.

Parameters:	shape_class (str) – Shape class directive, used for POS format (default: `None`). color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

class garnett.shapes.SphereShape(diameter, orientable=False, color=None)[source]¶

Shape class for spheres of a specified diameter.

Parameters:	diameter (float) – Diameter of the sphere. orientable (bool) – Set to True for spheres with orientation (default: `False`). color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> SphereShape(2.0).type_shape
{'type': 'Sphere', 'diameter': 2.0}

class garnett.shapes.ArrowShape(thickness=0.1, color=None)[source]¶

Shape class for arrows of a specified thickness.

Parameters:	thickness (float) – Thickness of the arrow. color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

class garnett.shapes.SphereUnionShape(diameters, centers, colors=None)[source]¶

Shape class for sphere unions, such as rigid bodies of many spheres.

Parameters:	diameters (list) – List of sphere diameters. centers (list) – List of 3D center vectors. colors (list) – List of hexadecimal color strings in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> SphereUnionShape([0.5, 0.5, 0.5], [[0, 0, 1.0], [0, 1.0, 0], [1.0, 0, 0]]).type_shape
{'type': 'SphereUnion', 'diameters': [0.5, 0.5, 0.5],
 'centers': [[0, 0, 1.0], [0, 1.0, 0], [1.0, 0, 0]]}

class garnett.shapes.PolygonShape(vertices, color=None)[source]¶

Shape class for polygons in a 2D plane.

Parameters:	vertices (list) – List of 2D vertex vectors. color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> PolygonShape([[-0.5, -0.5], [0.5, -0.5], [0.5, 0.5]]).type_shape
{'type': 'Polygon', 'rounding_radius': 0,
 'vertices': [[-0.5, -0.5], [0.5, -0.5], [0.5, 0.5]]}

class garnett.shapes.SpheropolygonShape(vertices, rounding_radius=0, color=None)[source]¶

Shape class for rounded polygons in a 2D plane.

Parameters:	vertices (list) – List of 2D vertex vectors. rounding_radius (float) – Rounding radius applied to the spheropolygon (default: 0). color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> SpheropolygonShape([[-0.5, -0.5], [0.5, -0.5], [0.5, 0.5]], 0.1).type_shape
{'type': 'Polygon', 'rounding_radius': 0.1,
 'vertices': [[-0.5, -0.5], [0.5, -0.5], [0.5, 0.5]]}

class garnett.shapes.ConvexPolyhedronShape(vertices, color=None)[source]¶

Shape class for convex polyhedra.

Parameters:	vertices (list) – List of 3D vertex vectors. color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> ConvexPolyhedronShape([[0.5, 0.5, 0.5], [0.5, -0.5, -0.5],
                           [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]]).type_shape
{'type': 'ConvexPolyhedron', 'rounding_radius': 0,
 'vertices': [[0.5, 0.5, 0.5], [0.5, -0.5, -0.5],
              [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]]}

class garnett.shapes.ConvexPolyhedronUnionShape(vertices, centers, orientations, colors=None)[source]¶

Shape class for unions of convex polyhedra.

Parameters:	vertices (list) – List of lists of 3D vertex vectors in particle coordinates (each polyhedron, each vertex). centers (list) – List of 3D polyhedra center vectors. orientations (list) – Orientations of the polyhedra, as a list of quaternions. colors (list) – List of hexadecimal color strings in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

class garnett.shapes.ConvexSpheropolyhedronShape(vertices, rounding_radius=0, color=None)[source]¶

Shape class for a convex polyhedron extended by a rounding radius.

Parameters:	vertices (list) – List of 3D vertex vectors. rounding_radius (float) – Rounding radius applied to the spheropolyhedron (default: 0). color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> ConvexSpheropolyhedronShape([[0.5, 0.5, 0.5], [0.5, -0.5, -0.5],
                                 [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]], 0.1).type_shape
{'type': 'ConvexPolyhedron', 'rounding_radius': 0.1,
 'vertices': [[0.5, 0.5, 0.5], [0.5, -0.5, -0.5],
              [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]]}

class garnett.shapes.GeneralPolyhedronShape(vertices, faces, color=None, facet_colors=None)[source]¶

Shape class for general polyhedra, such as arbitrary meshes.

Parameters:	vertices (list) – List of 3D vertex vectors. faces (list) – List of lists of integers representing vertex indices for each face. color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`). facet_colors (list) – List of hexadecimal color strings in format `RRGGBBAA` for each facet (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> GeneralPolyhedronShape([[0.5, 0.5, 0.5], [0.5, -0.5, -0.5],
                            [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]]).type_shape
{'type': 'Mesh',
 'vertices': [[0.5, 0.5, 0.5], [0.5, -0.5, -0.5],
              [-0.5, 0.5, -0.5], [-0.5, -0.5, 0.5]],
 'indices': [[0, 1, 2], [0, 1, 3], [0, 2, 3], [1, 2, 3]]}

class garnett.shapes.EllipsoidShape(a, b, c, color=None)[source]¶

Shape class for ellipsoids of with principal axes a, b, and c.

Parameters:	a (float) – Principal axis a of the ellipsoid (radius in the x direction). b (float) – Principal axis b of the ellipsoid (radius in the y direction). c (float) – Principal axis c of the ellipsoid (radius in the z direction). color (str) – Hexadecimal color string in format `RRGGBBAA` (default: `None`).

pos_string¶

type_shape¶

Shape as dictionary. Example:

>>> EllipsoidShape(7.0, 5.0, 3.0).type_shape
{'type': 'Ellipsoid',
 'a': 7.0,
 'b': 5.0,
 'c': 3.0}

Changelog¶

The garnett package follows semantic versioning.

Version 0.7¶

[0.7.1] – 2020-03-20¶

Fixed¶

Corrected package dependencies.

[0.7.0] – 2020-03-18¶

Added¶

Added ability to read _space_group_symop_operation_xyz keys in CIF files.
Added to_hoomd_snapshot method to Frame objects. Replaces the deprecated make_snapshot and copyto_snapshot methods.
The CIF reader supports a broader range of _atom_site_label values that match component 0 as specified here.
Enabled type_shape for SphereUnionShape class.
Added ability to read getar files with dynamic properties (such as type_shapes.json) stored at a different period than positions.
Added box property to Trajectory objects.
Added N property to Frame objects.

Changed¶

Updated GSD reader to use the GSD v2 API.
Changed behavior of types, typeid, type_shapes to match HOOMD conventions.
Shapes can still be read from GSD via HOOMD-HPMC state but shapes are always written to type_shapes instead of the HPMC state.
PosFileWriter requires the number of type_shapes to match the number of types.

Fixed¶

Fixed finding nearest image when applying space group operations to CIF files. The meaning of the tolerance parameter is also adjusted to be absolute (in units of fractional coordinates), rather than relative.

Deprecated¶

The following Frame and Trajectory attributes have been deprecated:
- positions (now position)
- orientations (now orientation)
- velocities (now velocity)
- shapedef dict has been replaced by type_shapes list. Until this feature is removed, altering shape definitions is only supported if the entire dictionary is set at once.
The following Frame methods have been deprecated:
- make_snapshot (use to_hoomd_snapshot())
- copyto_snapshot (use to_hoomd_snapshot(snap)
The following trajectory module-level functions have been deprecated:
- make_hoomd_blue_snapshot (use frame.to_hoomd_snapshot())
- copyfrom_hoomd_blue_snapshot (use Frame.from_hoomd_snapshot(snap))
- copyto_hoomd_blue_snapshot (use frame.to_hoomd_snapshot(snap))

Removed¶

The Frame.frame_data property and FrameData class have been removed from the public API.

Version 0.6¶

[0.6.1] – 2019-11-05¶

Fixed¶

Fix installation instructions with pip.
Removed unnecessary extra headers from changelog.

[0.6.0] – 2019-11-04¶

Added¶

Added showEdges to skipped fields when reading POS files.
Added to_plato_scene() method to quickly visualize Frame objects.
Added support for the GSD shape visualization specification.

Changed¶

GSD and GTAR writers now output shape information that adheres to the GSD shape visualization specification.

Removed¶

Dropped Python 2 support.

Fixed¶

Fix minor bug in PosFileWriter where default shape definition was incorrectly written.

Version 0.5¶

[0.5.0] – 2019-08-20¶

Added¶

Added rowan as a dependency.
Add GETAR file reader/writer.
Add shape_dict representation to Shape classes.
Add support for particle properties:
- mass
- charge
- diameter
- image
- moment of inertia
- angular momentum
Add support for reading/writing shapes in GSD via HOOMD-HPMC state.
Add universal reader/writer with format detection.
Add orientable attribute to spheres.
Extend list of supported shape classes:
- ellipsoid
- polygon
- spheropolygon
- convex polyhedron
- convex spheropolyhedron

Changed¶

Raise AttributeError if accessing a frame or trajectory property not defined in the file.
Rename several existing shape classes.
Improve unit test coverage.
Revise documentation.
Move shape definitions to separate module.

Deprecated¶

Tests for Python 2 are no longer updated (Python 2 support will be dropped in the next minor release).

Removed¶

Remove acceleration as supported property.
Remove the read_gsd_shape_data flag from GSD reader.

Version 0.4¶

[0.4.1] – 2017-08-23¶

Fixed¶

Fix minor bug related to QR check for 2d boxes.

[0.4.0] – 2017-06-26¶

Added¶

Add readers/writers:
- CIF reader
- GSD writer
Support shape definitions:
- spheropolyhedron
- polyunion
- convex polyhedron union
Add gf2pos script - convert to pos-file from any supported format.
Add shape definitions to GetarFileReader.
Interpret the pos-file rotation key word.

Changed¶

GetarFileReader skips records that have a non-empty group field.
Improve algorithm for the normalization of frames with non-standard box.
Various documentation updates.

Version 0.3¶

[0.3.9] – 2017-01-30¶

Added¶

The GSDReader now reads velocities.
Support PolyV shape definitions.

Changed¶

Update documentation concerning the conversion of rotations from quaternions to euler angles.

Fixed¶

Fix bug related to trajectory arrays when slicing the array.

[0.3.8] – 2016-12-21¶

Fixed¶

Hot fix: Negative euler angles were not read correctly in skewed boxes using the DCDFileReader.

[0.3.7] – 2016-11-07¶

Added¶

Add the whence argument to the file format’s seek method.

Fixed¶

Fix bug in DCDfilereader leading to incorrect box dimensions to be read for skewed boxes. Cubic or squared boxes are not affected.

[0.3.6] – 2016-10-20¶

Fixed¶

Fix quaternion to euler angle conversion example in the DCD file reader documentation.

[0.3.5] – 2016-09-20¶

Changed¶

GSDHOOMDFileReader uses the native GSD library if installed.
Reduced warning verbosity.

Fixed¶

Fix bug that caused the GSDHOOMDFileReader to ignore dimensions specified in the GSD file.

[0.3.4] – 2016-09-08¶

Added¶

Support velocities in HOOMD-blue XML files.
Support SphereUnionShape in PosFileReader.

Changed¶

Support Pos-Files using the keyword ‘box’ instead of ‘boxMatrix’

Fixed¶

Fix bug in PosFileReader which occured with non-standard pos-file in python 3.5
Fix bug, which occured when constructing frames from raw frames using box instances instead of a box matrix.

[0.3.3] – 2016-07-19¶

Fixed¶

Fix bug related to 2-dimensional systems and a box z-dimensions not equal to 1.

[0.3.2] – 2016-07-15¶

Added¶

Add trajectory.N, trajectory.type and trajectory.type_ids as an alternative mode to access frame length and type information.

Fixed¶

Fix bug in GSDHOOMDFileReader when not providing template frame.

[0.3.1] – 2016-07-08¶

Changed¶

Update the GSD hoomd module.

[0.3.0] – 2016-07-06¶

Added¶

Provide a highly optimized cythonized DCDFileReader.
Allow trajectory data acess via coherent numpy arrays.
Make snapshot creation and copying HOOMD-blue 2.0 compatible.

Changed¶

Update the GSD module.
Improve the Box class documentation.
Overall improvement of the documentation.

Fixed¶

Fix and optimize the pure-python DCDFileReader.

Version 0.2¶

[0.2.1] – 2016-07-10¶

Fixed¶

Fix an issue with injavis pos-files causing parser errors.

[0.2.0] – 2016-04-28¶

Fixed¶

Fix HOOMD-blue snapshot type issue.

Version 0.1¶

[0.1.9] – 2016-04-09¶

Added¶

Add GSDHoomdFileReader.

Fixed¶

Fix type issue in HoomdBlueXMLFileReader.

[0.1.8] – 2016-04-04¶

Added¶

Add HoomdBlueXMLFileReader.
Add DCDFileReader.
Add CifFileWriter.
Add GetarFileReader.

Fixed¶

Fix type issue in DCD.

[0.1.6] – 2016-01-28¶

Changed¶

Extend FileFormat API to increase file-like compatibility.

Fixed¶

Fixed box_matrix calculation.

[0.1.5] – 2016-01-11¶

Changed¶

Frames only loaded into memory on demand.
Improved trajectory iteration logic.

No change logs prior to v0.1.5¶

Developer’s Guide¶

Trajectory reader implementation¶

To implement a trajectory reader, first keep in mind that a garnett trajectory is simply a sequence of frames. This means that a trajectory reader needs to generate individual instances of frames.

To implement a new reader:

Provide a minimal sample for your format.

Create a new module in garnett with the name yourformatreader.py.

Specialize a frame class for your format called YourFormatFrame.

Implement the read() method for your frame, it should return an instance of garnett.trajectory._RawFrameData.
class YourFormatFrame(trajectory.Frame):

    def read():
        """Read the frame data from the stream.

        :returns: :class:`.trajectory._RawFrameData`
        """
Define a class YourFormatReader, where the constructor may take optional arguments for your reader.

The YourFormatReader class needs to implement a read() method.
class YourFormatReader(object):

    def read(stream):
        """Read the trajectory from stream.

        .. code::

            # pseudo-example
            frames = list(self.scan(stream))
            return trajectory.Trajectory(frames)

        :stream: A file-like object.
        :returns: :class:`.trajectory.Trajectory`
        """
Add your reader class to the __all__ directive in the garnett/reader.py module.

Provide a unit test for your reader, that reads a sample and generates a trajectory object accordingly.

For an example, please see the GSDHOOMDFileReader implementation.

Credits¶

Garnett Developers¶

The following people have contributed to the garnett package.

Carl Simon Adorf, University of Michigan

Original Author

Former Maintainer

Trajectory classes

Shapes classes

Testing framework

CIF file writer

DCD file reader

GSD file reader

HOOMD XML file reader

POS file reader

POS file writer

Richmond Newman, University of Michigan

Original Author

POS file reader

Matthew Spellings, University of Michigan

CIF file reader

GETAR file reader

Julia Dshemuchadse, University of Michigan

CIF file writer

Vyas Ramasubramani, University of Michigan

GSD file writer

Bradley Dice, University of Michigan

Maintainer

GETAR file writer

Support for additional frame properties

Improved support for parsing and writing particle shapes

Refactored types, typeid, type_shapes to match HOOMD conventions

Expanded support for CIF _atom_site_label types

Revised API for interfacing with frame data and HOOMD snapshots

Sophie Youjung Lee, University of Michigan

Former Maintainer

Universal read and write functions

Luis Y. Rivera-Rivera, University of Michigan

Maintainer

Various bugs and documentation fixes/updates

Implemented error handling for unstored properties

Improved dimension detection on GTAR and POS readers

Enabled GSD v2.0.0 compatibility

Added box to loadable trajectory attributes

Kelly Wang, University of Michigan

Maintainer

Paul Dodd, University of Michigan

Erin Teich, University of Michigan

Pablo Damasceno, University of Michigan

James Proctor, University of Michigan

Jens Glaser, University of Michigan

Mayank Agrawal, University of Michigan

Eric Harper, University of Michigan

Rose Cersonsky, University of Michigan

James Antonaglia, University of Michigan

Chengyu Dai, University of Michigan

Tim Moore, University of Michigan

GSD 2.0 compatibility

Source code¶

GSD is used to construct trajectory objects from GSD files and is available at https://github.com/glotzerlab/gsd. The files garnett/gsdhoomd.py and garnett/pygsd.py are directly copied from the GSD source code. GSD is used under the BSD license:

Copyright (c) 2016-2020 The Regents of the University of Michigan
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.