#include <itpp/comm/ldpc.h>
Definition at line 312 of file ldpc.h.
Public Member Functions | |
LDPC_Parity_Irregular () | |
Default constructor. | |
LDPC_Parity_Irregular (int Nvar, const vec &var_deg, const vec &chk_deg, const std::string &method="rand", const ivec &options="200 6") | |
Constructor that invokes generate() method. | |
void | generate (int Nvar, const vec &var_deg, const vec &chk_deg, const std::string &method="rand", const ivec &options="200 6") |
Generate an irregular LDPC code. | |
void | display_stats () const |
Display some information about the matrix. | |
int | cycle_removal_MGW (int L) |
Remove cycles (loops) from unstructured parity check matrix. | |
void | initialize (int ncheck, int nvar) |
Initialize an empty matrix of size ncheck x nvar. | |
GF2mat_sparse | get_H (bool transpose=false) const |
Get the parity check matrix, optionally its transposed form. | |
Sparse_Vec< bin > | get_col (int c) const |
Get a specific column from the matrix. | |
Sparse_Vec< bin > | get_row (int r) const |
Get a specific row from the matrix. | |
int | get_nvar () const |
Get the number of variable nodes (number of columns). | |
int | get_ncheck () const |
Get the number of check nodes (number of rows). | |
void | set (int i, int j, bin value) |
Set element (i,j) of the parity check matrix to value. | |
bin | get (int i, int j) const |
Get element (i,j) of the parity check matrix. | |
bin | operator() (int i, int j) const |
Get element (i,j) of the parity check matrix. | |
double | get_rate () const |
Get the code rate. | |
void | import_alist (const GF2mat_sparse_alist &H_alist) |
Import matrix from GF2mat_sparse_alist format. | |
GF2mat_sparse_alist | export_alist () const |
Export matrix to GF2mat_sparse_alist format. | |
void | load_alist (const std::string &alist_file) |
Load matrix from alist_file text file in alist format. | |
void | save_alist (const std::string &alist_file) const |
Save matrix to alist_file text file in alist format. | |
Protected Member Functions | |
void | generate_random_H (const ivec &C, const ivec &R, const ivec &cycopt) |
Generate a random parity check matrix. | |
int | check_for_cycles (int L) const |
Check for cycles of length L. | |
int | check_connectivity (int from_m, int from_n, int to_m, int to_n, int g, int L) const |
Check for connectivity between nodes. | |
Protected Attributes | |
bool | init_flag |
Flag that indicates proper initialization. | |
GF2mat_sparse | H |
The parity check matrix. | |
GF2mat_sparse | Ht |
The transposed parity check matrix. | |
int | nvar |
Number of variable nodes. | |
int | ncheck |
Number of check nodes. | |
ivec | sumX1 |
Actual number of ones in each column. | |
ivec | sumX2 |
Actual number of ones in each row. | |
Static Protected Attributes | |
static const int | Nmax = 200 |
Maximum node degree class can handle. |
void itpp::LDPC_Parity_Irregular::generate | ( | int | Nvar, | |
const vec & | var_deg, | |||
const vec & | chk_deg, | |||
const std::string & | method = "rand" , |
|||
const ivec & | options = "200 6" | |||
) |
Generate an irregular LDPC code.
Nvar | number of variable nodes | |
var_deg | vector of variable degree distributions, from an edge perspective | |
chk_deg | vector of check degree distributions, from an edge perspective | |
method | currently the only provided method is "rand" (see below) | |
options | Determines the level of matrix optimization. |
options
. In particular, the girth for the variable-node-degree-2 part of the graph can be controlled via the parameter options(0). The girth for the rest of the nodes can be controlled via the parameter options(1). The recommended value for options is "200 6" for graphs of small size, and "100 4" for large graphs. The value "0 0" means no optimization. Double edges are always avoided.
Alternative (user-defined) methods for code generation can be implemented by inheriting LDPC_Parity_Irregular
.
Definition at line 634 of file ldpc.cpp.
References itpp::find(), itpp::LDPC_Parity_Unstructured::generate_random_H(), it_error, itpp::length(), itpp::linspace(), itpp::max(), itpp::LDPC_Parity::Nmax, itpp::round(), itpp::sum(), itpp::to_ivec(), itpp::to_vec(), and itpp::zeros_i().
Referenced by LDPC_Parity_Irregular().
int itpp::LDPC_Parity_Unstructured::cycle_removal_MGW | ( | int | L | ) | [inherited] |
Remove cycles (loops) from unstructured parity check matrix.
This function implements the cycle removal algorithm presented by McGowan and Williamson at the IT workshop 2003. The maximum girth of the graph that will be attempted is L. The algorithm is bound to remove all loops of length L, insofar this is possible. I.e., it does not terminate until it is impossible to remove more cycles by swapping two edges.
L | Target girth. For example, L=6 attempts to removes all 4-cycles. |
Definition at line 290 of file ldpc.cpp.
References itpp::floor_i(), itpp::LDPC_Parity::get_col(), itpp::Sparse_Vec< T >::get_nz_index(), itpp::LDPC_Parity::init_flag, it_assert, it_assert_debug, it_info_debug, itpp::length(), itpp::LDPC_Parity::ncheck, itpp::Sparse_Vec< T >::nnz(), itpp::LDPC_Parity::nvar, itpp::randi(), itpp::randu(), and itpp::Array< T >::set_size().
int itpp::LDPC_Parity::check_for_cycles | ( | int | L | ) | const [protected, inherited] |
Check for cycles of length L.
This function implements a recursive routine to find loops. The function is mainly a tool for testing and debugging more sophisticated functions for graph manipulation.
L | length of cycles to look for |
Definition at line 247 of file ldpc.cpp.
References itpp::LDPC_Parity::check_connectivity(), itpp::LDPC_Parity::get_col(), itpp::LDPC_Parity::init_flag, it_assert, itpp::length(), and itpp::LDPC_Parity::nvar.
int itpp::LDPC_Parity::check_connectivity | ( | int | from_m, | |
int | from_n, | |||
int | to_m, | |||
int | to_n, | |||
int | g, | |||
int | L | |||
) | const [protected, inherited] |
Check for connectivity between nodes.
This function examines whether the point (to_m, to_n) in the matrix can be reached from the point (from_m, from_n) using at most L steps. A recursive search is used.
The function can be used to search for cycles in the matrix. To search for a cycle of length L, set from_m=to_m and from_n=to_n, and godir=0.
from_m | starting coordinate, row number | |
to_m | goal coordinate, row number | |
from_n | starting coordinate, column number | |
to_n | goal coordinate, row number | |
g | direction: 1=start going vertically, 2=start going horizontally | |
L | number of permitted steps |
Definition at line 190 of file ldpc.cpp.
References itpp::LDPC_Parity::get_col(), itpp::LDPC_Parity::get_row(), itpp::LDPC_Parity::init_flag, it_assert, and itpp::length().
Referenced by itpp::LDPC_Parity::check_for_cycles(), and itpp::LDPC_Parity_Unstructured::generate_random_H().
Generated on Sun Dec 9 17:31:11 2007 for IT++ by Doxygen 1.5.4