4.9. Utility functions¶
The utils
sub-namespace inside the LAMMPS_NS
namespace provides
a collection of convenience functions and utilities that perform common
tasks that are required repeatedly throughout the LAMMPS code like
reading or writing to files with error checking or translation of
strings into specific types of numbers with checking for validity. This
reduces redundant implementations and encourages consistent behavior.
4.9.1. I/O with status check and similar functions¶
The the first two functions are wrappers around the corresponding C
library calls fgets()
or fread()
. They will check if there
were errors on reading or an unexpected end-of-file state was reached.
In that case, the functions will stop with an error message, indicating
the name of the problematic file, if possible unless the error argument
is a NULL pointer.
The fgets_trunc()
function will work similar for fgets()
but it will read in a whole line (i.e. until the end of line or end
of file), but store only as many characters as will fit into the buffer
including a final newline character and the terminating NULL byte.
If the line in the file is longer it will thus be truncated in the buffer.
This function is used by read_lines_from_file()
to read individual
lines but make certain they follow the size constraints.
The read_lines_from_file()
function will read the requested
number of lines of a maximum length into a buffer and will return 0
if successful or 1 if not. It also guarantees that all lines are
terminated with a newline character and the entire buffer with a
NULL character.
-
void LAMMPS_NS::utils::sfgets(const char *srcname, int srcline, char *s, int size, FILE *fp, const char *filename, Error *error)¶
Safe wrapper around fgets() which aborts on errors or EOF and prints a suitable error message to help debugging.
Use nullptr as the error parameter to avoid the abort on EOF or error.
- Parameters
srcname – name of the calling source file (from FLERR macro)
srcline – line in the calling source file (from FLERR macro)
s – buffer for storing the result of fgets()
size – size of buffer s (max number of bytes read by fgets())
fp – file pointer used by fgets()
filename – file name associated with fp (may be a null pointer; then LAMMPS will try to detect)
error – pointer to Error class instance (for abort) or nullptr
-
void LAMMPS_NS::utils::sfread(const char *srcname, int srcline, void *s, size_t size, size_t num, FILE *fp, const char *filename, Error *error)¶
Safe wrapper around fread() which aborts on errors or EOF and prints a suitable error message to help debugging.
Use nullptr as the error parameter to avoid the abort on EOF or error.
- Parameters
srcname – name of the calling source file (from FLERR macro)
srcline – line in the calling source file (from FLERR macro)
s – buffer for storing the result of fread()
size – size of data elements read by fread()
num – number of data elements read by fread()
fp – file pointer used by fread()
filename – file name associated with fp (may be a null pointer; then LAMMPS will try to detect)
error – pointer to Error class instance (for abort) or nullptr
-
char *LAMMPS_NS::utils::fgets_trunc(char *s, int size, FILE *fp)¶
Wrapper around fgets() which reads whole lines but truncates the data to the buffer size and ensures a newline char at the end.
This function is useful for reading line based text files with possible comments that should be parsed later. This applies to data files, potential files, atomfile variable files and so on. It is used instead of fgets() by utils::read_lines_from_file().
- Parameters
s – buffer for storing the result of fgets()
size – size of buffer s (max number of bytes returned)
fp – file pointer used by fgets()
-
int LAMMPS_NS::utils::read_lines_from_file(FILE *fp, int nlines, int nmax, char *buffer, int me, MPI_Comm comm)¶
Read N lines of text from file into buffer and broadcast them
This function uses repeated calls to fread() to fill a buffer with newline terminated text. If a line does not end in a newline (e.g. at the end of a file), it is added. The caller has to allocate an nlines by nmax sized buffer for storing the text data. Reading is done by MPI rank 0 of the given communicator only, and thus only MPI rank 0 needs to provide a valid file pointer.
- Parameters
fp – file pointer used by fread
nlines – number of lines to be read
nmax – maximum length of a single line
buffer – buffer for storing the data.
me – MPI rank of calling process in MPI communicator
comm – MPI communicator for broadcast
- Returns
1 if the read was short, 0 if read was successful
4.9.2. String to number conversions with validity check¶
These functions should be used to convert strings to numbers. They are
are strongly preferred over C library calls like atoi()
or
atof()
since they check if the entire provided string is a valid
(floating-point or integer) number, and will error out instead of
silently returning the result of a partial conversion or zero in cases
where the string is not a valid number. This behavior allows to more
easily detect typos or issues when processing input files.
The do_abort flag should be set to true
in case this function
is called only on a single MPI rank, as that will then trigger the
a call to Error::one()
for errors instead of Error::all()
and avoids a “hanging” calculation when run in parallel.
Please also see is_integer()
and is_double()
for testing
strings for compliance without conversion.
-
double LAMMPS_NS::utils::numeric(const char *file, int line, const char *str, bool do_abort, LAMMPS *lmp)¶
Convert a string to a floating point number while checking if it is a valid floating point or integer number
- Parameters
file – name of source file for error message
line – line number in source file for error message
str – string to be converted to number
do_abort – determines whether to call Error::one() or Error::all()
lmp – pointer to top-level LAMMPS class instance
- Returns
double precision floating point number
-
int LAMMPS_NS::utils::inumeric(const char *file, int line, const char *str, bool do_abort, LAMMPS *lmp)¶
Convert a string to an integer number while checking if it is a valid integer number (regular int)
- Parameters
file – name of source file for error message
line – line number in source file for error message
str – string to be converted to number
do_abort – determines whether to call Error::one() or Error::all()
lmp – pointer to top-level LAMMPS class instance
- Returns
integer number (regular int)
-
bigint LAMMPS_NS::utils::bnumeric(const char *file, int line, const char *str, bool do_abort, LAMMPS *lmp)¶
Convert a string to an integer number while checking if it is a valid integer number (bigint)
- Parameters
file – name of source file for error message
line – line number in source file for error message
str – string to be converted to number
do_abort – determines whether to call Error::one() or Error::all()
lmp – pointer to top-level LAMMPS class instance
- Returns
integer number (bigint)
-
tagint LAMMPS_NS::utils::tnumeric(const char *file, int line, const char *str, bool do_abort, LAMMPS *lmp)¶
Convert a string to an integer number while checking if it is a valid integer number (tagint)
- Parameters
file – name of source file for error message
line – line number in source file for error message
str – string to be converted to number
do_abort – determines whether to call Error::one() or Error::all()
lmp – pointer to top-level LAMMPS class instance
- Returns
integer number (tagint)
4.9.3. String processing¶
The following are functions to help with processing strings and parsing files or arguments.
-
char *LAMMPS_NS::utils::strdup(const std::string &text)¶
Make C-style copy of string in new storage
This allocates a storage buffer and copies the C-style or C++ style string into it. The buffer is allocated with “new” and thus needs to be deallocated with “delete[]”.
- Parameters
text – string that should be copied
- Returns
new buffer with copy of string
-
std::string LAMMPS_NS::utils::trim(const std::string &line)¶
Trim leading and trailing whitespace. Like TRIM() in Fortran.
- Parameters
line – string that should be trimmed
- Returns
new string without whitespace (string)
-
std::string LAMMPS_NS::utils::trim_comment(const std::string &line)¶
Return string with anything from ‘#’ onward removed
- Parameters
line – string that should be trimmed
- Returns
new string without comment (string)
-
inline bool LAMMPS_NS::utils::has_utf8(const std::string &line)¶
Check if a string will likely have UTF-8 encoded characters
UTF-8 uses the 7-bit standard ASCII table for the first 127 characters and all other characters are encoded as multiple bytes. For the multi-byte characters the first byte has either the highest two, three, or four bits set followed by a zero bit and followed by one, two, or three more bytes, respectively, where the highest bit is set and the second highest bit set to 0. The remaining bits combined are the character code, which is thus limited to 21-bits.
For the sake of efficiency this test only checks if a character in the string has the highest bit set and thus is very likely an UTF-8 character. It will not be able to tell this this is a valid UTF-8 character or whether it is a 2-byte, 3-byte, or 4-byte character.
- See also
- Parameters
line – string that should be checked
- Returns
true if string contains UTF-8 encoded characters (bool)
-
std::string LAMMPS_NS::utils::utf8_subst(const std::string &line)¶
Replace known UTF-8 characters with ASCII equivalents
- See also
- Parameters
line – string that should be converted
- Returns
new string with ascii replacements (string)
-
size_t LAMMPS_NS::utils::count_words(const char *text)¶
Count words in C-string, ignore any whitespace matching ” \t\r\n\f”
- Parameters
text – string that should be searched
- Returns
number of words found
-
size_t LAMMPS_NS::utils::count_words(const std::string &text)¶
Count words in string, ignore any whitespace matching ” \t\r\n\f”
- Parameters
text – string that should be searched
- Returns
number of words found
-
size_t LAMMPS_NS::utils::count_words(const std::string &text, const std::string &separators)¶
Count words in string with custom choice of separating characters
- Parameters
text – string that should be searched
separators – string containing characters that will be treated as whitespace
- Returns
number of words found
-
size_t LAMMPS_NS::utils::trim_and_count_words(const std::string &text, const std::string &separators = " \t\r\n\f")¶
Count words in a single line, trim anything from ‘#’ onward
- Parameters
text – string that should be trimmed and searched
separators – string containing characters that will be treated as whitespace
- Returns
number of words found
-
std::vector<std::string> LAMMPS_NS::utils::split_words(const std::string &text)¶
Take text and split into non-whitespace words.
This can handle strings with single and double quotes, escaped quotes, and escaped codes within quotes, but due to using an STL container and STL strings is rather slow because of making copies. Designed for parsing command lines and similar text and not for time critical processing. Use a tokenizer class if performance matters.
- See also
- Parameters
text – string that should be split
- Returns
STL vector with the words
-
std::vector<std::string> LAMMPS_NS::utils::split_lines(const std::string &text)¶
Take multi-line text and split into lines
- Parameters
text – string that should be split
- Returns
STL vector with the lines
-
bool LAMMPS_NS::utils::strmatch(const std::string &text, const std::string &pattern)¶
Match text against a simplified regex pattern
More flexible and specific matching of a string against a pattern. This function is supposed to be a more safe, more specific and simple to use API to find pattern matches. The purpose is to replace uses of either strncmp() or strstr() in the code base to find sub-strings safely. With strncmp() finding prefixes, the number of characters to match must be counted, which can lead to errors, while using “^pattern” will do the same with less problems. Matching for suffixes using strstr() is not as specific as ‘pattern$’, and complex matches, e.g. “^rigid.*\/small.*”, to match all small body optimized rigid fixes require only one test.
The use of std::string arguments allows for simple concatenation even with char * type variables. Example: utils::strmatch(text, std::string(“^”) + charptr)
- Parameters
text – the text to be matched against the pattern
pattern – the search pattern, which may contain regexp markers
- Returns
true if the pattern matches, false if not
-
std::string LAMMPS_NS::utils::strfind(const std::string &text, const std::string &pattern)¶
Find sub-string that matches a simplified regex pattern
This function is a companion function to utils::strmatch(). Arguments and logic is the same, but instead of a boolean, it returns the sub-string that matches the regex pattern. There can be only one match. This can be used as a more flexible alternative to strstr().
- Parameters
text – the text to be matched against the pattern
pattern – the search pattern, which may contain regexp markers
- Returns
the string that matches the pattern or an empty one
-
bool LAMMPS_NS::utils::is_integer(const std::string &str)¶
Check if string can be converted to valid integer
- Parameters
str – string that should be checked
- Returns
true, if string contains valid a integer, false otherwise
-
bool LAMMPS_NS::utils::is_double(const std::string &str)¶
Check if string can be converted to valid floating-point number
- Parameters
str – string that should be checked
- Returns
true, if string contains valid number, false otherwise
4.9.4. File and path functions¶
-
const char *LAMMPS_NS::utils::guesspath(char *buf, int len, FILE *fp)¶
Try to detect pathname from FILE pointer.
Currently only supported on Linux, otherwise will report “(unknown)”.
On Linux the folder /proc/self/fd holds symbolic links to the actual pathnames associated with each open file descriptor of the current process.
This function is used to provide a filename with error messages in functions where the filename is not passed as an argument, but the FILE * pointer.
- Parameters
buf – storage buffer for pathname. output will be truncated if not large enough
len – size of storage buffer. output will be truncated to this length - 1
fp – FILE pointer struct from STDIO library for which we want to detect the name
- Returns
pointer to the storage buffer, i.e. buf
-
std::string LAMMPS_NS::utils::path_basename(const std::string &path)¶
Strip off leading part of path, return just the filename
- Parameters
path – file path
- Returns
file name
-
std::string LAMMPS_NS::utils::path_join(const std::string &a, const std::string &b)¶
Join two pathname segments
This uses the forward slash ‘/’ character unless LAMMPS is compiled for Windows where it used the equivalent backward slash ‘'.
- Parameters
a – first path
b – second path
- Returns
combined path
-
bool LAMMPS_NS::utils::file_is_readable(const std::string &path)¶
Check if file exists and is readable
- Parameters
path – file path
- Returns
true if file exists and is readable
4.9.5. Potential file functions¶
-
std::string LAMMPS_NS::utils::get_potential_file_path(const std::string &path)¶
Determine full path of potential file. If file is not found in current directory, search directories listed in LAMMPS_POTENTIALS environment variable
- Parameters
path – file path
- Returns
full path to potential file
-
std::string LAMMPS_NS::utils::get_potential_date(const std::string &path, const std::string &potential_name)¶
Read potential file and return DATE field if it is present
- Parameters
path – file path
potential_name – name of potential that is being read
- Returns
DATE field if present
-
std::string LAMMPS_NS::utils::get_potential_units(const std::string &path, const std::string &potential_name)¶
Read potential file and return UNITS field if it is present
- Parameters
path – file path
potential_name – name of potential that is being read
- Returns
UNITS field if present
-
int LAMMPS_NS::utils::get_supported_conversions(const int property)¶
Return bitmask of available conversion factors for a given property
- Parameters
property – property to be converted
- Returns
bitmask indicating available conversions
-
double LAMMPS_NS::utils::get_conversion_factor(const int property, const int conversion)¶
Return unit conversion factor for given property and selected from/to units
- Parameters
property – property to be converted
conversion – constant indicating the conversion
- Returns
conversion factor
-
FILE *LAMMPS_NS::utils::open_potential(const std::string &name, LAMMPS *lmp, int *auto_convert)¶
Open a potential file as specified by name
If opening the file directly fails, the function will search for it in the list of folder pointed to by the environment variable
LAMMPS_POTENTIALS
(if it is set).If the potential file has a
UNITS
tag in the first line, the tag’s value is compared to the current unit style setting. The behavior of the function then depends on the value of the auto_convert parameter. If it is a null pointer, then the unit values must match or else the open will fail with an error. Otherwise the bitmask that auto_convert points to is used check for compatibility with possible automatic conversions by the calling function. If compatible, the bitmask is set to the required conversion orutils::NOCONVERT
.- Parameters
name – file- or pathname of the potential file
lmp – pointer to top-level LAMMPS class instance
auto_convert – pointer to unit conversion bitmask or
nullptr
- Returns
FILE pointer of the opened potential file or
nullptr
4.9.6. Argument processing¶
-
template<typename TYPE>
void LAMMPS_NS::utils::bounds(const char *file, int line, const std::string &str, bigint nmin, bigint nmax, TYPE &nlo, TYPE &nhi, Error *error)¶ Compute index bounds derived from a string with a possible wildcard
This functions processes the string in str and set the values of nlo and nhi according to the following five cases:
a single number, i: nlo = i; nhi = i;
a single asterisk, *: nlo = nmin; nhi = nmax;
a single number followed by an asterisk, i*: nlo = i; nhi = nmax;
a single asterisk followed by a number, *i: nlo = nmin; nhi = i;
two numbers with an asterisk in between. i*j: nlo = i; nhi = j;
- Parameters
file – name of source file for error message
line – line number in source file for error message
str – string to be processed
nmin – smallest possible lower bound
nmax – largest allowed upper bound
nlo – lower bound
nhi – upper bound
error – pointer to Error class for out-of-bounds messages
-
int LAMMPS_NS::utils::expand_args(const char *file, int line, int narg, char **arg, int mode, char **&earg, LAMMPS *lmp)¶
Expand list of arguments when containing fix/compute wildcards
This function searches the list of arguments in arg for strings of the kind c_ID[*] or f_ID[*] referring to computes or fixes. Any such strings are replaced by one or more strings with the ‘*’ character replaced by the corresponding possible numbers as determined from the fix or compute instance. Other strings are just copied. If the mode parameter is set to 0, expand global vectors, but not global arrays; if it is set to 1, expand global arrays (by column) but not global vectors.
If any expansion happens, the earg list and all its strings are new allocations and must be freed explicitly by the caller. Otherwise arg and earg will point to the same address and no explicit de-allocation is needed by the caller.
- Parameters
file – name of source file for error message
line – line number in source file for error message
narg – number of arguments in current list
arg – argument list, possibly containing wildcards
mode – select between global vectors(=0) and arrays (=1)
earg – new argument list with wildcards expanded
lmp – pointer to top-level LAMMPS class instance
- Returns
number of arguments in expanded list
4.9.7. Convenience functions¶
-
template<typename S, typename ...Args>
void LAMMPS_NS::utils::logmesg(LAMMPS *lmp, const S &format, Args&&... args)¶ Send formatted message to screen and logfile, if available
This function simplifies the repetitive task of outputting some message to both the screen and/or the log file. The template wrapper with fmtlib format and argument processing allows this function to work similar to
fmt::print()
.- Parameters
lmp – pointer to LAMMPS class instance
format – format string of message to be printed
args – arguments to format string
-
void LAMMPS_NS::utils::logmesg(LAMMPS *lmp, const std::string &mesg)¶
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
- Parameters
lmp – pointer to LAMMPS class instance
mesg – string with message to be printed
-
std::string LAMMPS_NS::utils::getsyserror()¶
Return a string representing the current system error status
This is a wrapper around calling strerror(errno).
- Returns
error string
-
std::string LAMMPS_NS::utils::check_packages_for_style(const std::string &style, const std::string &name, LAMMPS *lmp)¶
Report if a requested style is in a package or may have a typo
- Parameters
style – type of style that is to be checked for
name – name of style that was not found
lmp – pointer to top-level LAMMPS class instance
- Returns
string usable for error messages
-
double LAMMPS_NS::utils::timespec2seconds(const std::string ×pec)¶
Convert a time string to seconds
The strings “off” and “unlimited” result in -1
- Parameters
timespec – a string in the following format: ([[HH:]MM:]SS)
- Returns
total in seconds
-
int LAMMPS_NS::utils::date2num(const std::string &date)¶
Convert a LAMMPS version date to a number
This will generate a number YYYYMMDD from a date string (with or without blanks) that is suitable for numerical comparisons, i.e. later dates will generate a larger number.
The day may or may not have a leading zero, the month is identified by the first 3 letters (so there may be more) and the year may be 2 or 4 digits (the missing 2 digits will be assumed as 20. That is 04 corresponds to 2004).
No check is made whether the date is valid.
- Parameters
date – string in the format (Day Month Year)
- Returns
date code
4.9.8. Customized standard functions¶
-
void LAMMPS_NS::utils::merge_sort(int *index, int num, void *ptr, int (*comp)(int, int, void*))¶
Custom merge sort implementation
This function provides a custom upward hybrid merge sort implementation with support to pass an opaque pointer to the comparison function, e.g. for access to class members. This avoids having to use global variables. For improved performance, it uses an in-place insertion sort on initial chunks of up to 64 elements and switches to merge sort from then on.
- Parameters
index – Array with indices to be sorted
num – Length of the index array
ptr – Pointer to opaque object passed to comparison function
comp – Pointer to comparison function
4.10. Tokenizer classes¶
The purpose of the tokenizer classes is to simplify the recurring task
of breaking lines of text down into words and/or numbers.
Traditionally, LAMMPS code would be using the strtok()
function from
the C library for that purpose, but that function has two significant
disadvantages: 1) it cannot be used concurrently from different LAMMPS
instances since it stores its status in a global variable and 2) it
modifies the string that it is processing. These classes were
implemented to avoid both of these issues and also to reduce the amount
of code that needs to be written.
The basic procedure is to create an instance of the tokenizer class with the string to be processed as an argument and then do a loop until all available tokens are read. The constructor has a default set of separator characters, but that can be overridden. The default separators are all “whitespace” characters, i.e. the space character, the tabulator character, the carriage return character, the linefeed character, and the form feed character.
#include "tokenizer.h"
#include <cstdlib>
#include <string>
#include <iostream>
using namespace LAMMPS_NS;
int main(int, char **)
{
const char *path = getenv("PATH");
if (path != nullptr) {
Tokenizer p(path,":");
while (p.has_next())
std::cout << "Entry: " << p.next() << "\n";
}
return 0;
}
Most tokenizer operations cannot fail except for
LAMMPS_NS::Tokenizer::next()
(when used without first
checking with LAMMPS_NS::Tokenizer::has_next()
) and
LAMMPS_NS::Tokenizer::skip()
. In case of failure, the class
will throw an exception, so you may need to wrap the code using the
tokenizer into a try
/ catch
block to handle errors. The
LAMMPS_NS::ValueTokenizer
class may also throw an exception
when a (type of) number is requested as next token that is not
compatible with the string representing the next word.
#include "tokenizer.h"
#include <cstdlib>
#include <string>
#include <iostream>
using namespace LAMMPS_NS;
int main(int, char **)
{
const char *text = "1 2 3 4 5 20.0 21 twentytwo 2.3";
double num1(0),num2(0),num3(0),num4(0);
ValueTokenizer t(text);
// read 4 doubles after skipping over 5 numbers
try {
t.skip(5);
num1 = t.next_double();
num2 = t.next_double();
num3 = t.next_double();
num4 = t.next_double();
} catch (TokenizerException &e) {
std::cout << "Reading numbers failed: " << e.what() << "\n";
}
std::cout << "Values: " << num1 << " " << num2 << " " << num3 << " " << num4 << "\n";
return 0;
}
This code example should produce the following output:
Reading numbers failed: Not a valid floating-point number: 'twentytwo'
Values: 20 21 0 0
-
class LAMMPS_NS::Tokenizer¶
Public Functions
-
Tokenizer(const std::string &str, const std::string &separators = TOKENIZER_DEFAULT_SEPARATORS)¶
Class for splitting text into words
This tokenizer will break down a string into sub-strings (i.e words) separated by the given separator characters. If the string contains certain known UTF-8 characters they will be replaced by their ASCII equivalents processing the string.
- Parameters
str – string to be processed
separators – string with separator characters (default: ” \t\r\n\f”)
-
void reset()¶
Re-position the tokenizer state to the first word, i.e. the first non-separator character
-
void skip(int n = 1)¶
Skip over a given number of tokens
- Parameters
n – number of tokens to skip over
-
bool has_next() const¶
Indicate whether more tokens are available
- Returns
true if there are more tokens, false if not
-
bool contains(const std::string &str) const¶
Search the text to be processed for a sub-string.
- Parameters
str – string to be searched for
- Returns
true if string was found, false if not
-
std::string next()¶
Retrieve next token.
- Returns
string with the next token
-
size_t count()¶
Count number of tokens in text.
- Returns
number of counted tokens
-
std::vector<std::string> as_vector()¶
Retrieve the entire text converted to an STL vector of tokens.
- Returns
The STL vector
-
Tokenizer(const std::string &str, const std::string &separators = TOKENIZER_DEFAULT_SEPARATORS)¶
-
class LAMMPS_NS::TokenizerException : public exception¶
Subclassed by InvalidFloatException, InvalidIntegerException
Public Functions
-
TokenizerException(const std::string &msg, const std::string &token)¶
Thrown during retrieving or skipping tokens
- Parameters
msg – String with error message
token – String of the token/word that caused the error
-
inline virtual const char *what() const¶
Retrieve message describing the thrown exception
- Returns
string with error message
-
TokenizerException(const std::string &msg, const std::string &token)¶
-
class LAMMPS_NS::ValueTokenizer¶
Public Functions
-
ValueTokenizer(const std::string &str, const std::string &separators = TOKENIZER_DEFAULT_SEPARATORS)¶
Class for reading text with numbers
- See also
- See
Tokenizer InvalidIntegerException InvalidFloatException
- Parameters
str – String to be processed
separators – String with separator characters (default: ” \t\r\n\f”)
-
std::string next_string()¶
Retrieve next token
- Returns
string with next token
-
tagint next_tagint()¶
Retrieve next token and convert to tagint
- Returns
value of next token
-
bigint next_bigint()¶
Retrieve next token and convert to bigint
- Returns
value of next token
-
int next_int()¶
Retrieve next token and convert to int
- Returns
value of next token
-
double next_double()¶
Retrieve next token and convert to double
- Returns
value of next token
-
bool has_next() const¶
Indicate whether more tokens are available
- Returns
true if there are more tokens, false if not
-
bool contains(const std::string &value) const¶
Search the text to be processed for a sub-string.
- Parameters
value – string with value to be searched for
- Returns
true if string was found, false if not
-
void skip(int ntokens = 1)¶
Skip over a given number of tokens
- Parameters
n – number of tokens to skip over
-
size_t count()¶
Count number of tokens in text.
- Returns
number of counted tokens
-
ValueTokenizer(const std::string &str, const std::string &separators = TOKENIZER_DEFAULT_SEPARATORS)¶
-
class InvalidIntegerException : public TokenizerException¶
-
class InvalidFloatException : public TokenizerException¶
4.11. Argument parsing classes¶
The purpose of argument parsing classes it to simplify and unify how arguments of commands in LAMMPS are parsed and to make abstractions of repetitive tasks.
The LAMMPS_NS::ArgInfo
class provides an abstraction
for parsing references to compute or fix styles, variables or custom
integer or double properties handled by fix property/atom.
These would start with a “c_”, “f_”, “v_”, “d_”, “d2_”, “i_”, or “i2_”
followed by the ID or name of than instance and may be postfixed with
one or two array indices “[<number>]” with numbers > 0.
A typical code segment would look like this:
int nvalues = 0;
for (iarg = 0; iarg < nargnew; iarg++) {
ArgInfo argi(arg[iarg]);
which[nvalues] = argi.get_type();
argindex[nvalues] = argi.get_index1();
ids[nvalues] = argi.copy_name();
if ((which[nvalues] == ArgInfo::UNKNOWN)
|| (which[nvalues] == ArgInfo::NONE)
|| (argi.get_dim() > 1))
error->all(FLERR,"Illegal compute XXX command");
nvalues++;
}
-
class LAMMPS_NS::ArgInfo¶
Public Types
-
enum ArgTypes¶
constants for argument types
Values:
-
enumerator ERROR¶
-
enumerator UNKNOWN¶
-
enumerator NONE¶
-
enumerator X¶
-
enumerator V¶
-
enumerator F¶
-
enumerator COMPUTE¶
-
enumerator FIX¶
-
enumerator VARIABLE¶
-
enumerator KEYWORD¶
-
enumerator TYPE¶
-
enumerator MOLECULE¶
-
enumerator DNAME¶
-
enumerator INAME¶
-
enumerator DENSITY_NUMBER¶
-
enumerator DENSITY_MASS¶
-
enumerator MASS¶
-
enumerator TEMPERATURE¶
-
enumerator BIN1D¶
-
enumerator BIN2D¶
-
enumerator BIN3D¶
-
enumerator BINSPHERE¶
-
enumerator BINCYLINDER¶
-
enumerator ERROR¶
Public Functions
-
ArgInfo(const std::string &arg, int allowed = COMPUTE | FIX | VARIABLE)¶
Class for processing references to fixes, computes and variables
This class provides an abstraction for the repetitive task of parsing arguments that may contain references to fixes, computes, variables, or custom per-atom properties. It will identify the name and the index value in the first and second dimension, if present.
- Parameters
arg – string with possible reference
allowed – integer with bitmap of allowed types of references
-
inline int get_type() const¶
get type of reference
Return a type constant for the reference. This may be either COMPUTE, FIX, VARIABLE (if not restricted to a subset of those by the “allowed” argument of the constructor) or NONE, if it if not a recognized or allowed reference, or UNKNOWN, in case some error happened identifying or parsing the values of the indices
- Returns
integer with a constant from ArgTypes enumerator
-
inline int get_dim() const¶
get dimension of reference
This will return either 0, 1, 2 depending on whether the reference has no, one or two “[{number}]” postfixes.
- Returns
integer with the dimensionality of the reference
-
inline int get_index1() const¶
get index of first dimension
This will return the number in the first “[{number}]” postfix or 0 if there is no postfix.
- Returns
integer with index or the postfix or 0
-
inline int get_index2() const¶
get index of second dimension
This will return the number in the second “[{number}]” postfix or -1 if there is no second postfix.
- Returns
integer with index of the postfix or -1
-
inline const char *get_name() const¶
return reference to the ID or name of the reference
This string is pointing to an internal storage element and is only valid to use while the ArgInfo class instance is in scope. If you need a long-lived string make a copy with copy_name().
- Returns
C-style char * string
-
char *copy_name()¶
make copy of the ID of the reference as C-style string
The ID is copied into a buffer allocated with “new” and thus must be later deleted with “delete []” to avoid a memory leak. Because it is a full copy in a newly allocated buffer, the lifetime of this string extends beyond the the time the ArgInfo class is in scope.
- Returns
copy of string as char *
-
enum ArgTypes¶
4.12. File reader classes¶
The purpose of the file reader classes is to simplify the recurring task
of reading and parsing files. They can use the
LAMMPS_NS::ValueTokenizer
class to process the read in
text. The LAMMPS_NS::TextFileReader
is a more general
version while LAMMPS_NS::PotentialFileReader
is specialized
to implement the behavior expected for looking up and reading/parsing
files with potential parameters in LAMMPS. The potential file reader
class requires a LAMMPS instance, requires to be run on MPI rank 0 only,
will use the LAMMPS_NS::utils::get_potential_file_path()
function to look up and open the file, and will call the
LAMMPS_NS::Error
class in case of failures to read or to
convert numbers, so that LAMMPS will be aborted.
PotentialFileReader reader(lmp, file, "coul/streitz");
char * line;
while((line = reader.next_line(NPARAMS_PER_LINE))) {
try {
ValueTokenizer values(line);
std::string iname = values.next_string();
int ielement;
for (ielement = 0; ielement < nelements; ielement++)
if (iname == elements[ielement]) break;
if (nparams == maxparam) {
maxparam += DELTA;
params = (Param *) memory->srealloc(params,maxparam*sizeof(Param),
"pair:params");
}
params[nparams].ielement = ielement;
params[nparams].chi = values.next_double();
params[nparams].eta = values.next_double();
params[nparams].gamma = values.next_double();
params[nparams].zeta = values.next_double();
params[nparams].zcore = values.next_double();
} catch (TokenizerException & e) {
error->one(FLERR, e.what());
}
nparams++;
}
A file that would be parsed by the reader code fragment looks like this:
# DATE: 2015-02-19 UNITS: metal CONTRIBUTOR: Ray Shan CITATION: Streitz and Mintmire, Phys Rev B, 50, 11996-12003 (1994) # # X (eV) J (eV) gamma (1/AA) zeta (1/AA) Z (e) Al 0.000000 10.328655 0.000000 0.968438 0.763905 O 5.484763 14.035715 0.000000 2.143957 0.000000
-
class LAMMPS_NS::TextFileReader¶
Public Functions
-
TextFileReader(const std::string &filename, const std::string &filetype)¶
Class for reading and parsing text files
The value of the class member variable ignore_comments controls whether any text following the pound sign (#) should be ignored (true) or not (false). Default: true, i.e. ignore.
- See also
- Parameters
filename – Name of file to be read
filetype – Description of file type for error messages
-
TextFileReader(FILE *fp, const std::string &filetype)¶
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
This function is useful in combination with
utils::open_potential()
.Note
The FILE pointer is not closed in the destructor, but will be advanced when reading from it.
- Parameters
fp – File descriptor of the already opened file
filetype – Description of file type for error messages
-
~TextFileReader()¶
Closes the file
-
void skip_line()¶
Read the next line and ignore it
-
char *next_line(int nparams = 0)¶
Read the next line(s) until nparams words have been read.
This reads a line and counts the words in it, if the number is less than the requested number, it will read the next line, as well. Output will be a string with all read lines combined. The purpose is to somewhat replicate the reading behavior of formatted files in Fortran.
If the ignore_comments class member has the value true, then any text read in is truncated at the first ‘#’ character.
- Parameters
nparams – Number of words that must be read. Default: 0
- Returns
String with the concatenated text
-
void next_dvector(double *list, int n)¶
Read lines until n doubles have been read and stored in array list
This reads lines from the file using the next_line() function, and splits them into floating-point numbers using the ValueTokenizer class and stores the number is the provided list.
- Parameters
list – Pointer to array with suitable storage for n doubles
n – Number of doubles to be read
-
ValueTokenizer next_values(int nparams, const std::string &separators = TOKENIZER_DEFAULT_SEPARATORS)¶
Read text until nparams words are read and passed to a tokenizer object for custom parsing.
This reads lines from the file using the next_line() function, and splits them into floating-point numbers using the ValueTokenizer class and stores the number is the provided list.
- Parameters
nparams – Number of words to be read
separators – String with list of separators.
- Returns
ValueTokenizer object for read in text
Public Members
-
bool ignore_comments¶
Controls whether comments are ignored.
-
TextFileReader(const std::string &filename, const std::string &filetype)¶
-
class LAMMPS_NS::PotentialFileReader : protected Pointers¶
Public Functions
-
PotentialFileReader(class LAMMPS *lmp, const std::string &filename, const std::string &potential_name, const std::string &name_suffix, const int auto_convert = 0)¶
Class for reading and parsing LAMMPS potential files
The value of the class member variable ignore_comments controls whether any text following the pound sign (#) should be ignored (true) or not (false). Default: true, i.e. ignore.
- See also
- Parameters
lmp – Pointer to LAMMPS instance
filename – Name of file to be read
potential_name – Name of potential style for error messages
name_suffix – Suffix added to potential name in error messages
auto_convert – Bitmask of supported unit conversions
-
virtual ~PotentialFileReader()¶
Closes the file
-
void ignore_comments(bool value)¶
Set comment (= text after ‘#’) handling preference for the file to be read
- Parameters
value – Comment text is ignored if true, or not if false
-
void skip_line()¶
Read a line but ignore its content
-
char *next_line(int nparams = 0)¶
Read the next line(s) until nparams words have been read.
This reads a line and counts the words in it, if the number is less than the requested number, it will read the next line, as well. Output will be a string with all read lines combined. The purpose is to somewhat replicate the reading behavior of formatted files in Fortran.
- Parameters
nparams – Number of words that must be read. Default: 0
- Returns
String with the concatenated text
-
void next_dvector(double *list, int n)¶
Read lines until n doubles have been read and stored in array list
This reads lines from the file using the next_line() function, and splits them into floating-point numbers using the ValueTokenizer class and stores the number is the provided list.
- Parameters
list – Pointer to array with suitable storage for n doubles
n – Number of doubles to be read
-
ValueTokenizer next_values(int nparams, const std::string &separators = TOKENIZER_DEFAULT_SEPARATORS)¶
Read text until nparams words are read and passed to a tokenizer object for custom parsing.
This reads lines from the file using the next_line() function, and splits them into floating-point numbers using the ValueTokenizer class and stores the number is the provided list.
- Parameters
nparams – Number of words to be read
separators – String with list of separators.
- Returns
ValueTokenizer object for read in text
-
double next_double()¶
Read next line and convert first word to a double
- Returns
Value of first word in line as double
-
int next_int()¶
Read next line and convert first word to an int
- Returns
Value of first word in line as int
-
tagint next_tagint()¶
Read next line and convert first word to a tagint
- Returns
Value of first word in line as tagint
-
bigint next_bigint()¶
Read next line and convert first word to a bigint
- Returns
Value of first word in line as bigint
-
std::string next_string()¶
Read next line and return first word
- Returns
First word of read in line
-
PotentialFileReader(class LAMMPS *lmp, const std::string &filename, const std::string &potential_name, const std::string &name_suffix, const int auto_convert = 0)¶
4.13. Memory pool classes¶
The memory pool classes are used for cases where otherwise many small memory allocations would be needed and where the data would be either all used or all freed. One example for that is the storage of neighbor lists. The memory management strategy is based on the assumption that allocations will be in chunks of similar sizes. The allocation is then not done per individual call for a reserved chunk of memory, but for a “page” that can hold multiple chunks of data. A parameter for the maximum chunk size must be provided, as that is used to determine whether a new page of memory must be used.
The MyPage
class offers two ways to
reserve a chunk: 1) with get()
the
chunk size needs to be known in advance, 2) with vget()
a pointer to the next chunk is returned, but
its size is registered later with vgot()
.
#include "my_page.h"
using namespace LAMMPS_NS;
MyPage<double> *dpage = new MyPage<double>;
// max size of chunk: 256, size of page: 10240 doubles (=81920 bytes)
dpage->init(256,10240);
double **build_some_lists(int num)
{
dpage->reset();
double **dlist = new double*[num];
for (int i=0; i < num; ++i) {
double *dptr = dpage.vget();
int jnum = 0;
for (int j=0; j < jmax; ++j) {
// compute some dvalue for eligible loop index j
dptr[j] = dvalue;
++jnum;
}
if (dpage.status() != 0) {
// handle out of memory or jnum too large errors
}
dpage.vgot(jnum);
dlist[i] = dptr;
}
return dlist;
}
-
class LAMMPS_NS::MyPage¶
Templated class for storing chunks of datums in pages.
The size of the chunk may vary from call to call, but must be less or equal than the maxchunk setting. The chunks are not returnable like with malloc() (i.e. you cannot call free() on them individually). One can only reset and start over. The purpose of this class is to replace many small memory allocations via malloc() with a few large ones. Since the pages are never freed until the class is re-initialized, they can be re-used without having to re-allocate them by calling the reset() method.
The settings maxchunk, pagesize, and pagedelta control the memory allocation strategy. The maxchunk value represents the expected largest number of items per chunk. If there is less space left on the current page, a new page is allocated for the next chunk. The pagesize value represents how many items can fit on a single page. It should have space for multiple chunks of size maxchunk. The combination of these two parameters determines how much memory is wasted by either switching to the next page too soon or allocating too large pages that never get properly used. It is an error, if a requested chunk is larger than maxchunk. The pagedelta parameter determines how many pages are allocated in one go. In combination with the pagesize setting, this determines how often blocks of memory get allocated (fewer allocations will result in faster execution).
Note
This is a template class with explicit instantiation. If the class is used with a new data type a new explicit instantiation may need to be added at the end of the file
src/my_page.cpp
to avoid symbol lookup errors.Public Functions
-
int init(int user_maxchunk = 1, int user_pagesize = 1024, int user_pagedelta = 1)¶
(Re-)initialize the set of pages and allocation parameters.
This also frees all previously allocated storage and allocates the first page(s).
- Parameters
user_maxchunk – Expected maximum number of items for one chunk
user_pagesize – Number of items on a single memory page
user_pagedelta – Number of pages to allocate with one malloc
- Returns
1 if there were invalid parameters, 2 if there was an allocation error or 0 if successful
-
T *get(int n = 1)¶
Pointer to location that can store N items.
This will allocate more pages as needed. If the parameter N is larger than the maxchunk setting an error is flagged.
- Parameters
n – number of items for which storage is requested
- Returns
memory location or null pointer, if error or allocation failed
-
inline T *vget()¶
Get pointer to location that can store maxchunk items.
This will return the same pointer as the previous call to this function unless vgot() is called afterwards to record how many items of the chunk were actually used.
- Returns
pointer to chunk of memory or null pointer if run out of memory
-
inline void vgot(int n)¶
Mark N items as used of the chunk reserved with a preceding call to vget().
This will advance the internal pointer inside the current memory page. It is not necessary to call this function for N = 0, that is the reserved storage was not used. A following call to vget() will then reserve the same location again. It is an error if N > maxchunk.
- Parameters
n – Number of items used in previously reserved chunk
-
void reset()¶
Reset state of memory pool without freeing any memory
-
inline double size() const¶
Return total size of allocated pages
- Returns
total storage used in bytes
-
inline int status() const¶
Return error status
- Returns
0 if no error, 1 requested chunk size > maxchunk, 2 if malloc failed
-
int init(int user_maxchunk = 1, int user_pagesize = 1024, int user_pagedelta = 1)¶
-
class LAMMPS_NS::MyPoolChunk¶
Templated class for storing chunks of datums in pages.
The size of the chunk may vary from call to call between the minchunk and maxchunk setting. Chunks may be returned to the pool for re-use. Chunks can be reserved in nbin different sizes between minchunk and maxchunk. The chunksperpage setting specifies how many chunks are stored on any page and the pagedelta setting determines how many pages are allocated in one go. Pages are never freed, so they can be re-used without re-allocation.
Note
This is a template class with explicit instantiation. If the class is used with a new data type a new explicit instantiation may need to be added at the end of the file
src/my_pool_chunk.cpp
to avoid symbol lookup errors.Public Functions
-
MyPoolChunk(int user_minchunk = 1, int user_maxchunk = 1, int user_nbin = 1, int user_chunkperpage = 1024, int user_pagedelta = 1)¶
Create a class instance and set memory pool parameters
- Parameters
user_minchunk – Minimal chunk size
user_maxchunk – Maximal chunk size
user_nbin – Number of bins of different chunk sizes
user_chunkperpage – Number of chunks per page
user_pagedelta – Number of pages to allocate in one go
-
~MyPoolChunk()¶
Destroy class instance and free all allocated memory
-
T *get(int &index)¶
Return pointer/index of unused chunk of size maxchunk
- Parameters
index – Index of chunk in memory pool
- Returns
Pointer to requested chunk of storage
-
T *get(int n, int &index)¶
Return pointer/index of unused chunk of size N
- Parameters
n – Size of chunk
index – Index of chunk in memory pool
- Returns
Pointer to requested chunk of storage
-
void put(int index)¶
Put indexed chunk back into memory pool via free list
- Parameters
index – Memory chunk index returned by call to get()
-
double size() const¶
Return total size of allocated pages
- Returns
total storage used in bytes
-
inline int status() const¶
Return error status
- Returns
0 if no error, 1 if invalid input, 2 if malloc() failed, 3 if chunk > maxchunk
-
MyPoolChunk(int user_minchunk = 1, int user_maxchunk = 1, int user_nbin = 1, int user_chunkperpage = 1024, int user_pagedelta = 1)¶
4.14. Eigensolver functions¶
The MathEigen
sub-namespace of the LAMMPS_NS
namespace contains
functions and classes for eigensolvers. Currently only the
jacobi3 function
is used in various
places in LAMMPS. That function is built on top of a group of more
generic eigensolvers that are maintained in the math_eigen_impl.h
header file. This header contains the implementation of three template
classes:
“Jacobi” calculates all of the eigenvalues and eigenvectors of a dense, symmetric, real matrix.
The “PEigenDense” class only calculates the principal eigenvalue (ie. the largest or smallest eigenvalue), and its corresponding eigenvector. However it is much more efficient than “Jacobi” when applied to large matrices (larger than 13x13). PEigenDense also can understand complex-valued Hermitian matrices.
The “LambdaLanczos” class is a generalization of “PEigenDense” which can be applied to arbitrary sparse matrices.
The “math_eigen_impl.h” code is an amalgamation of jacobi_pd by Andrew Jewett at Scripps Research (under CC0-1.0 license) and Lambda Lanczos by Yuya Kurebayashi at Tohoku University (under MIT license)
-
int MathEigen::jacobi3(double const *const *mat, double *eval, double **evec)¶
A specialized function which finds the eigenvalues and eigenvectors of a 3x3 matrix (in double ** format).
- Parameters
mat – the 3x3 matrix you wish to diagonalize
eval – store the eigenvalues here
evec – store the eigenvectors here…
- Returns
0 if eigenvalue calculation converged, 1 if it failed
-
int MathEigen::jacobi3(double const mat[3][3], double *eval, double evec[3][3])¶
This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.
4.15. Communication buffer coding with ubuf¶
LAMMPS uses communication buffers where it collects data from various
class instances and then exchanges the data with neighboring sub-domains.
For simplicity those buffers are defined as double
buffers and
used for doubles and integer numbers. This presents a unique problem
when 64-bit integers are used. While the storage needed for a double
is also 64-bit, it cannot be used by a simple assignment. To get around
that limitation, LAMMPS uses the ubuf
union. It is used in the various “pack” and “unpack” functions in the
LAMMPS classes to store and retrieve integers that may be 64-bit from
the communication buffers.
-
union LAMMPS_NS::ubuf¶
- #include <lmptype.h>
Data structure for packing 32-bit and 64-bit integers into double (communication) buffers
Using this union avoids aliasing issues by having member types (double, int) referencing the same buffer memory location.
The explicit constructor for 32-bit integers prevents compilers from (incorrectly) calling the double constructor when storing an int into a double buffer.
Usage:
double buf[2]; int foo = 1; tagint bar = 2<<40; buf[1] = ubuf(foo).d; buf[2] = ubuf(bar).d;
foo = (int) ubuf(buf[1]).i; bar = (tagint) ubuf(buf[2]).i;
The typecasts prevent compiler warnings about possible truncation issues.