"""This module is for reading ACE-format cross sections. ACE stands for "A
Compact ENDF" format and originated from work on MCNP_. It is used in a number
of other Monte Carlo particle transport codes.
ACE-format cross sections are typically generated from ENDF_ files through a
cross section processing program like NJOY_. The ENDF data consists of tabulated
thermal data, ENDF/B resonance parameters, distribution parameters in the
unresolved resonance region, and tabulated data in the fast region. After the
ENDF data has been reconstructed and Doppler-broadened, the ACER module
generates ACE-format cross sections.
.. _MCNP: https://laws.lanl.gov/vhosts/mcnp.lanl.gov/
.. _NJOY: http://t2.lanl.gov/codes.shtml
.. _ENDF: http://www.nndc.bnl.gov/endf
"""
from __future__ import division, unicode_literals
from os import SEEK_CUR
import struct
import sys
from six import string_types
import numpy as np
from openmc.mixin import EqualityMixin
from openmc.data.endf import ENDF_FLOAT_RE
[docs]def ascii_to_binary(ascii_file, binary_file):
"""Convert an ACE file in ASCII format (type 1) to binary format (type 2).
Parameters
----------
ascii_file : str
Filename of ASCII ACE file
binary_file : str
Filename of binary ACE file to be written
"""
# Open ASCII file
ascii = open(ascii_file, 'r')
# Set default record length
record_length = 4096
# Read data from ASCII file
lines = ascii.readlines()
ascii.close()
# Open binary file
binary = open(binary_file, 'wb')
idx = 0
while idx < len(lines):
# check if it's a > 2.0.0 version header
if lines[idx].split()[0][1] == '.':
if lines[idx + 1].split()[3] == '3':
idx = idx + 3
else:
raise NotImplementedError('Only backwards compatible ACE'
'headers currently supported')
# Read/write header block
hz = lines[idx][:10].encode('UTF-8')
aw0 = float(lines[idx][10:22])
tz = float(lines[idx][22:34])
hd = lines[idx][35:45].encode('UTF-8')
hk = lines[idx + 1][:70].encode('UTF-8')
hm = lines[idx + 1][70:80].encode('UTF-8')
binary.write(struct.pack(str('=10sdd10s70s10s'), hz, aw0, tz, hd, hk, hm))
# Read/write IZ/AW pairs
data = ' '.join(lines[idx + 2:idx + 6]).split()
iz = list(map(int, data[::2]))
aw = list(map(float, data[1::2]))
izaw = [item for sublist in zip(iz, aw) for item in sublist]
binary.write(struct.pack(str('=' + 16*'id'), *izaw))
# Read/write NXS and JXS arrays. Null bytes are added at the end so
# that XSS will start at the second record
nxs = list(map(int, ' '.join(lines[idx + 6:idx + 8]).split()))
jxs = list(map(int, ' '.join(lines[idx + 8:idx + 12]).split()))
binary.write(struct.pack(str('=16i32i{0}x'.format(record_length - 500)),
*(nxs + jxs)))
# Read/write XSS array. Null bytes are added to form a complete record
# at the end of the file
n_lines = (nxs[0] + 3)//4
xss = list(map(float, ' '.join(lines[
idx + 12:idx + 12 + n_lines]).split()))
extra_bytes = record_length - ((len(xss)*8 - 1) % record_length + 1)
binary.write(struct.pack(str('={0}d{1}x'.format(nxs[0], extra_bytes)),
*xss))
# Advance to next table in file
idx += 12 + n_lines
# Close binary file
binary.close()
def get_table(filename, name=None):
"""Read a single table from an ACE file
Parameters
----------
filename : str
Path of the ACE library to load table from
name : str, optional
Name of table to load, e.g. '92235.71c'
Returns
-------
openmc.data.ace.Table
ACE table with specified name. If no name is specified, the first table
in the file is returned.
"""
lib = Library(filename)
if name is None:
return lib.tables[0]
else:
for table in lib.tables:
if table.name == name:
return table
else:
raise ValueError('Could not find ACE table with name: {}'
.format(name))
[docs]class Library(EqualityMixin):
"""A Library objects represents an ACE-formatted file which may contain
multiple tables with data.
Parameters
----------
filename : str
Path of the ACE library file to load.
table_names : None, str, or iterable, optional
Tables from the file to read in. If None, reads in all of the
tables. If str, reads in only the single table of a matching name.
verbose : bool, optional
Determines whether output is printed to the stdout when reading a
Library
Attributes
----------
tables : list
List of :class:`Table` instances
"""
def __init__(self, filename, table_names=None, verbose=False):
if isinstance(table_names, string_types):
table_names = [table_names]
if table_names is not None:
table_names = set(table_names)
self.tables = []
# Determine whether file is ASCII or binary
try:
fh = open(filename, 'rb')
# Grab 10 lines of the library
sb = b''.join([fh.readline() for i in range(10)])
# Try to decode it with ascii
sb.decode('ascii')
# No exception so proceed with ASCII - reopen in non-binary
fh.close()
with open(filename, 'r') as fh:
fh.seek(0)
self._read_ascii(fh, table_names, verbose)
except UnicodeDecodeError:
fh.close()
with open(filename, 'rb') as fh:
self._read_binary(fh, table_names, verbose)
def _read_binary(self, ace_file, table_names, verbose=False,
recl_length=4096, entries=512):
"""Read a binary (Type 2) ACE table.
Parameters
----------
ace_file : file
Open ACE file
table_names : None, str, or iterable
Tables from the file to read in. If None, reads in all of the
tables. If str, reads in only the single table of a matching name.
verbose : str, optional
Whether to display what tables are being read. Defaults to False.
recl_length : int, optional
Fortran record length in binary file. Default value is 4096 bytes.
entries : int, optional
Number of entries per record. The default is 512 corresponding to a
record length of 4096 bytes with double precision data.
"""
while True:
start_position = ace_file.tell()
# Check for end-of-file
if len(ace_file.read(1)) == 0:
return
ace_file.seek(start_position)
# Read name, atomic mass ratio, temperature, date, comment, and
# material
name, atomic_weight_ratio, temperature, date, comment, mat = \
struct.unpack(str('=10sdd10s70s10s'), ace_file.read(116))
name = name.decode().strip()
# Read ZAID/awr combinations
data = struct.unpack(str('=' + 16*'id'), ace_file.read(192))
pairs = list(zip(data[::2], data[1::2]))
# Read NXS
nxs = list(struct.unpack(str('=16i'), ace_file.read(64)))
# Determine length of XSS and number of records
length = nxs[0]
n_records = (length + entries - 1)//entries
# verify that we are supposed to read this table in
if (table_names is not None) and (name not in table_names):
ace_file.seek(start_position + recl_length*(n_records + 1))
continue
if verbose:
kelvin = round(temperature * 1e6 / 8.617342e-5)
print("Loading nuclide {0} at {1} K".format(name, kelvin))
# Read JXS
jxs = list(struct.unpack(str('=32i'), ace_file.read(128)))
# Read XSS
ace_file.seek(start_position + recl_length)
xss = list(struct.unpack(str('={0}d'.format(length)),
ace_file.read(length*8)))
# Insert zeros at beginning of NXS, JXS, and XSS arrays so that the
# indexing will be the same as Fortran. This makes it easier to
# follow the ACE format specification.
nxs.insert(0, 0)
nxs = np.array(nxs, dtype=int)
jxs.insert(0, 0)
jxs = np.array(jxs, dtype=int)
xss.insert(0, 0.0)
xss = np.array(xss)
# Create ACE table with data read in
table = Table(name, atomic_weight_ratio, temperature, pairs,
nxs, jxs, xss)
self.tables.append(table)
# Advance to next record
ace_file.seek(start_position + recl_length*(n_records + 1))
def _read_ascii(self, ace_file, table_names, verbose=False):
"""Read an ASCII (Type 1) ACE table.
Parameters
----------
ace_file : file
Open ACE file
table_names : None, str, or iterable
Tables from the file to read in. If None, reads in all of the
tables. If str, reads in only the single table of a matching name.
verbose : str, optional
Whether to display what tables are being read. Defaults to False.
"""
tables_seen = set()
lines = [ace_file.readline() for i in range(13)]
while len(lines) != 0 and lines[0].strip() != '':
# Read name of table, atomic mass ratio, and temperature. If first
# line is empty, we are at end of file
# check if it's a 2.0 style header
if lines[0].split()[0][1] == '.':
words = lines[0].split()
name = words[1]
words = lines[1].split()
atomic_weight_ratio = float(words[0])
temperature = float(words[1])
commentlines = int(words[3])
for i in range(commentlines):
lines.pop(0)
lines.append(ace_file.readline())
else:
words = lines[0].split()
name = words[0]
atomic_weight_ratio = float(words[1])
temperature = float(words[2])
datastr = ' '.join(lines[2:6]).split()
pairs = list(zip(map(int, datastr[::2]),
map(float, datastr[1::2])))
datastr = '0 ' + ' '.join(lines[6:8])
nxs = np.fromstring(datastr, sep=' ', dtype=int)
n_lines = (nxs[1] + 3)//4
n_bytes = len(lines[-1]) * (n_lines - 2) + 1
# Ensure that we have more tables to read in
if (table_names is not None) and (table_names < tables_seen):
break
tables_seen.add(name)
# verify that we are suppossed to read this table in
if (table_names is not None) and (name not in table_names):
ace_file.seek(n_bytes, SEEK_CUR)
ace_file.readline()
lines = [ace_file.readline() for i in range(13)]
continue
# read and fix over-shoot
lines += ace_file.readlines(n_bytes)
if 12 + n_lines < len(lines):
goback = sum([len(line) for line in lines[12+n_lines:]])
lines = lines[:12+n_lines]
ace_file.seek(-goback, SEEK_CUR)
if verbose:
kelvin = round(temperature * 1e6 / 8.617342e-5)
print("Loading nuclide {0} at {1} K".format(name, kelvin))
# Insert zeros at beginning of NXS, JXS, and XSS arrays so that the
# indexing will be the same as Fortran. This makes it easier to
# follow the ACE format specification.
datastr = '0 ' + ' '.join(lines[8:12])
jxs = np.fromstring(datastr, dtype=int, sep=' ')
datastr = '0.0 ' + ''.join(lines[12:12+n_lines])
xss = np.fromstring(datastr, sep=' ')
# When NJOY writes an ACE file, any values less than 1e-100 actually
# get written without the 'e'. Thus, what we do here is check
# whether the xss array is of the right size (if a number like
# 1.0-120 is encountered, np.fromstring won't capture any numbers
# after it). If it's too short, then we apply the ENDF float regular
# expression. We don't do this by default because it's expensive!
if xss.size != nxs[1] + 1:
datastr = ENDF_FLOAT_RE.sub(r'\1e\2', datastr)
xss = np.fromstring(datastr, sep=' ')
assert xss.size == nxs[1] + 1
table = Table(name, atomic_weight_ratio, temperature, pairs,
nxs, jxs, xss)
self.tables.append(table)
# Read all data blocks
lines = [ace_file.readline() for i in range(13)]
[docs]class Table(EqualityMixin):
"""ACE cross section table
Parameters
----------
name : str
ZAID identifier of the table, e.g. '92235.70c'.
atomic_weight_ratio : float
Atomic mass ratio of the target nuclide.
temperature : float
Temperature of the target nuclide in MeV.
pairs : list of tuple
16 pairs of ZAIDs and atomic weight ratios. Used for thermal scattering
tables to indicate what isotopes scattering is applied to.
nxs : numpy.ndarray
Array that defines various lengths with in the table
jxs : numpy.ndarray
Array that gives locations in the ``xss`` array for various blocks of
data
xss : numpy.ndarray
Raw data for the ACE table
"""
def __init__(self, name, atomic_weight_ratio, temperature, pairs,
nxs, jxs, xss):
self.name = name
self.atomic_weight_ratio = atomic_weight_ratio
self.temperature = temperature
self.pairs = pairs
self.nxs = nxs
self.jxs = jxs
self.xss = xss
def __repr__(self):
return "<ACE Table: {}>".format(self.name)