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Axel Kohlmeyer
2022-05-02 13:41:03 -04:00
parent df77641071 fef6c37ea7
commit 8473bc19f5
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138
doc/src/Howto_structured_data.rst
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@ -55,6 +55,9 @@ JSON
YAML format thermo_style output
===============================
Extracting data from log file
-----------------------------
.. versionadded:: 24Mar2022
LAMMPS supports the thermo style "yaml" and for "custom" style
@ -66,7 +69,7 @@ the following style:
.. code-block:: yaml
---
keywords: [Step, Temp, E_pair, E_mol, TotEng, Press, ]
keywords: ['Step', 'Temp', 'E_pair', 'E_mol', 'TotEng', 'Press', ]
data:
- [100, 0.757453103239935, -5.7585054860159, 0, -4.62236133677021, 0.207261053624721, ]
- [110, 0.759322359337036, -5.7614668389562, 0, -4.62251889318624, 0.194314975399602, ]
@ -80,9 +83,9 @@ This data can be extracted and parsed from a log file using python with:
import re, yaml
try:
from yaml import CSafeLoader as Loader, CSafeDumper as Dumper
from yaml import CSafeLoader as Loader
except ImportError:
from yaml import SafeLoader as Loader, SafeDumper as Dumper
from yaml import SafeLoader as Loader
docs = ""
with open("log.lammps") as f:
@ -109,6 +112,135 @@ of that run:
Number of runs: 2
TotEng = -4.62140097780047
.. versionadded:: 4May2022
YAML format output has been added to multiple commands in LAMMPS,
for example :doc:`dump yaml <dump>` or :doc:`fix ave/time <fix_ave_time>`
Depending on the kind of data being written, organization of the data
or the specific syntax used may change, but the principles are very
similar and all files should be readable with a suitable YAML parser.
Processing scalar data with Python
----------------------------------
.. figure:: JPG/thermo_bondeng.png
:figwidth: 33%
:align: right
After reading and parsing the YAML format data, it can be easily
imported for further processing and visualization with the `pandas
<https://pandas.pydata.org/>`_ and `matplotlib
<https://matplotlib.org/>`_ Python modules. Because of the organization
of the data in the YAML format thermo output, it needs to be told to
process only the 'data' part of the imported data to create a pandas
data frame, and one needs to set the column names from the 'keywords'
entry. The following Python script code example demonstrates this, and
creates the image shown on the right of a simple plot of various bonded
energy contributions versus the timestep from a run of the 'peptide'
example input after changing the :doc:`thermo style <thermo_style>` to
'yaml'. The properties to be used for x and y values can be
conveniently selected through the keywords. Please note that those
keywords can be changed to custom strings with the :doc:`thermo_modify
colname <thermo_modify>` command.
.. code-block:: python
import re, yaml
import pandas as pd
import matplotlib.pyplot as plt
try:
from yaml import CSafeLoader as Loader
except ImportError:
from yaml import SafeLoader as Loader
docs = ""
with open("log.lammps") as f:
for line in f:
m = re.search(r"^(keywords:.*$|data:$|---$|\.\.\.$| - \[.*\]$)", line)
if m: docs += m.group(0) + '\n'
thermo = list(yaml.load_all(docs, Loader=Loader))
df = pd.DataFrame(data=thermo[0]['data'], columns=thermo[0]['keywords'])
fig = df.plot(x='Step', y=['E_bond', 'E_angle', 'E_dihed', 'E_impro'], ylabel='Energy in kcal/mol')
plt.savefig('thermo_bondeng.png')
Processing vector data with Python
----------------------------------
Global *vector* data as produced by :doc:`fix ave/time <fix_ave_time>`
uses a slightly different organization of the data. You still have the
dictionary keys 'keywords' and 'data' for the column headers and the
data. But the data is a dictionary indexed by the time step and for
each step there are multiple rows of values each with a list of the
averaged properties. This requires a slightly different processing,
since the entire data cannot be directly imported into a single pandas
DataFrame class instance. The following Python script example
demonstrates how to read such data. The result will combine the data
for the different steps into one large "multi-index" table. The pandas
IndexSlice class can then be used to select data from this combined data
frame.
.. code-block:: python
import re, yaml
import pandas as pd
try:
from yaml import CSafeLoader as Loader
except ImportError:
from yaml import SafeLoader as Loader
with open("ave.yaml") as f:
ave = yaml.load(docs, Loader=Loader)
keys = ave['keywords']
df = {}
for k in ave['data'].keys():
df[k] = pd.DataFrame(data=ave['data'][k], columns=keys)
# create multi-index data frame
df = pd.concat(df)
# output only the first 3 value for steps 200 to 300 of the column Pressure
idx = pd.IndexSlice
print(df['Pressure'].loc[idx[200:300, 0:2]])
Processing scalar data with Perl
--------------------------------
The ease of processing YAML data is not limited to Python. Here is an
example for extracting and processing a LAMMPS log file with Perl instead.
.. code-block:: perl
use YAML::XS;
open(LOG, "log.lammps") or die("could not open log.lammps: $!");
my $file = "";
while(my $line = <LOG>) {
if ($line =~ /^(keywords:.*$|data:$|---$|\.\.\.$| - \[.*\]$)/) {
$file .= $line;
}
}
close(LOG);
# convert YAML to perl as nested hash and array references
my $thermo = Load $file;
# convert references to real arrays
my @keywords = @{$thermo->{'keywords'}};
my @data = @{$thermo->{'data'}};
# print first two columns
print("$keywords[0] $keywords[1]\n");
foreach (@data) {
print("${$_}[0] ${$_}[1]\n");
}
Writing continuous data during a simulation
===========================================

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22
doc/src/fix_ave_time.rst
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@ -272,10 +272,18 @@ each input value specified in the fix ave/time command. For *mode* =
scalar, this means a single line is written each time output is
performed. Thus the file ends up to be a series of lines, i.e. one
column of numbers for each input value. For *mode* = vector, an array
of numbers is written each time output is performed. The number of
rows is the length of the input vectors, and the number of columns is
the number of values. Thus the file ends up to be a series of these
array sections.
of numbers is written each time output is performed. The number of rows
is the length of the input vectors, and the number of columns is the
number of values. Thus the file ends up to be a series of these array
sections.
If the filename ends in '.yaml' or '.yml' then the output format
conforms to the `YAML standard <https://yaml.org/>`_ which allows
easy import that data into tools and scripts that support reading YAML
files. The :doc:`structured data Howto <Howto_structured_data>` contains
examples for parsing and plotting such data with very little programming
effort in Python using the *pyyaml*, *pandas*, and *matplotlib*
packages.
The *overwrite* keyword will continuously overwrite the output file
with the latest output, so that it only contains one timestep worth of
@ -321,8 +329,10 @@ appropriate fields from the fix ave/time command.
Restart, fix_modify, output, run start/stop, minimize info
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
No information about this fix is written to :doc:`binary restart files <restart>`. None of the :doc:`fix_modify <fix_modify>` options
are relevant to this fix.
No information about this fix is written to :doc:`binary restart files
<restart>`. The :doc:`fix_modify colname <fix_modify>` option can be
used to change the name of the column in the output file. When writing
a YAML format file this name will be in the list of keywords.
This fix produces a global scalar or global vector or global array
which can be accessed by various :doc:`output commands <Howto_output>`.

38
doc/src/fix_modify.rst
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@ -12,19 +12,23 @@ Syntax
* fix-ID = ID of the fix to modify
* one or more keyword/value pairs may be appended
* keyword = *temp* or *press* or *energy* or *virial* or *respa* or *dynamic/dof* or *bodyforces*
* keyword = *bodyforces* or *colname* or *dynamic/dof* or *energy* or *press* or *respa* or *temp* or *virial*
.. parsed-literal::
*temp* value = compute ID that calculates a temperature
*press* value = compute ID that calculates a pressure
*energy* value = *yes* or *no*
*virial* value = *yes* or *no*
*respa* value = *1* to *max respa level* or *0* (for outermost level)
*dynamic/dof* value = *yes* or *no*
yes/no = do or do not re-compute the number of degrees of freedom (DOF) contributing to the temperature
*bodyforces* value = *early* or *late*
early/late = compute rigid-body forces/torques early or late in the timestep
*colname* values = ID string
string = new column header name
ID = integer from 1 to N, or integer from -1 to -N, where N = # of quantities being output
*or* a fix output property keyword or reference to compute, fix, property or variable.
*dynamic/dof* value = *yes* or *no*
yes/no = do or do not re-compute the number of degrees of freedom (DOF) contributing to the temperature
*energy* value = *yes* or *no*
*press* value = compute ID that calculates a pressure
*respa* value = *1* to *max respa level* or *0* (for outermost level)
*temp* value = compute ID that calculates a temperature
*virial* value = *yes* or *no*
Examples
""""""""
@ -34,6 +38,7 @@ Examples
fix_modify 3 temp myTemp press myPress
fix_modify 1 energy yes
fix_modify tether respa 2
fix_modify ave colname c_thermo_press Pressure colname 1 Temperature
Description
"""""""""""
@ -165,6 +170,20 @@ will have no effect on the motion of the rigid bodies if they are
specified in the input script after the fix rigid command. LAMMPS
will give a warning if that is the case.
The *colname* keyword can be used to change the default header keywords
in output files of fix styles that support it: currently only :doc:`fix
ave/time <fix_ave_time>` is supported. The setting for *ID string*
replaces the default text with the provided string. *ID* can be a
positive integer when it represents the column number counting from the
left, a negative integer when it represents the column number from the
right (i.e. -1 is the last column/keyword), or a custom fix output
keyword (or compute, fix, property, or variable reference) and then it
replaces the string for that specific keyword. The *colname* keyword can
be used multiple times. If multiple *colname* settings refer to the same
keyword, the last setting has precedence.
Restrictions
""""""""""""
none
@ -172,7 +191,8 @@ none
Related commands
""""""""""""""""
:doc:`fix <fix>`, :doc:`compute temp <compute_temp>`, :doc:`compute pressure <compute_pressure>`, :doc:`thermo_style <thermo_style>`
:doc:`fix <fix>`, :doc:`compute temp <compute_temp>`,
:doc:`compute pressure <compute_pressure>`, :doc:`thermo_style <thermo_style>`
Default
"""""""