Generation of LDPC codes

// Generate some example LDPC codes

#include <itpp/itcomm.h>

using namespace itpp;
using namespace std;

int main(int argc, char **argv)
{
  { // This generates a random regular (3,6) code with 500 bits
    cout << "========= RANDOM (3,6) CODE ==========" << endl;
    LDPC_Parity_Regular H;
    H.generate(500, 3, 6,
               "rand",  // random unstructured matrix
               "500 10");   // optimize girth
    H.display_stats();
    LDPC_Code C1(&H);
    C1.save_code("random_3_6_code.it");
  }

  { // This is the code "204.33.484 (N=204, K=102, M=102, R=0.5)" from
    // David MacKay's database over sparse-graph code. It can be obtained
    // using the following URL:
    // http://www.inference.phy.cam.ac.uk/mackay/codes/EN/C/204.33.484
    cout << "========= MACKAY CODE ==========" << endl;
    LDPC_Parity_Regular H;
    H.load_alist("204.33.484");
    H.display_stats();
    LDPC_Generator_Systematic G(&H);
    LDPC_Code C(&H, &G);
    C.save_code("mackay_204.33.484.it");

    // Now produce a girth-optimized version of this code by removing
    // cycles. This slightly improves the performance at high SNR.
    // Cycle removal procedure is only available for unstructured LDPC
    // parity check matrices, represented by either LDPC_Parity_Regular or
    // LDPC_Parity_Irregular classes.
    H.cycle_removal_MGW(12);
    LDPC_Generator_Systematic G1(&H);
    LDPC_Code C1(&H, &G1);
    C1.save_code("mackay_204.33.484_opt.it");
  }

  // Irregular 1/2-rate codes optimized for the AWGN channel. The
  // degree distributions are taken from Richardson & Urbanke,
  // Trans. IT 2001.

  { // 1000 bits
    cout << "========= IRREGULAR CODE 1000 BITS ==========" << endl;
    LDPC_Parity_Irregular H;
    H.generate(1000,
               "0 0.27684 0.28342 0 0 0 0 0 0.43974",
               "0 0 0 0 0 0.01568 0.85244 0.13188",
               "rand",   // random unstructured matrix
               "500 8"); // optimize girth
    LDPC_Code C(&H);
    C.save_code("RU_1000.it");
  }

  {  // 10000 bits (takes a few minutes to run)
    cout << "========= IRREGULAR CODE 10000 BITS ==========" << endl;
    LDPC_Parity_Irregular H;
    H.generate(10000,
               "0 0.21991 0.23328 0.02058 0 0.08543 0.06540 0.04767 0.01912 "
               "0 0 0 0 0 0 0 0 0 0.08064 0.22798",
               "0 0 0 0 0 0 0 0.64854 0.34747 0.00399",
               "rand",  // random unstructured matrix
               "150 8"); // optimize
    LDPC_Code C(&H);
    C.save_code("RU_10000.it");
  }

  { // 100000 bits (takes a while to run)
    cout << "========= IRREGULAR CODE 100000 BITS ==========" << endl;
    LDPC_Parity_Irregular H;
    H.generate(100000,
               "0 0.1712 0.21053 0.00273 0 0 0.00009 0.15269 0.09227 "
               "0.02802 0 0 0 0 0.01206 0 0 0 0 0 0 0 0 0 0 0 0 0 0 "
               "0.07212 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.25830",
               "0 0 0 0 0 0 0 0 0.33620 0.08883 0.57497",
               "rand",
               "40 4");  // less aggressive optimization
    LDPC_Code C(&H);
    C.save_code("RU_100000.it");
  }

  return 0;

  { // 1000000 bits (THIS CODE REQUIRES ABOUT 450 MB TO STORE AND 2GB
    // INTERNAL MEMORY TO GENERATE)
    cout << "========= IRREGULAR CODE 1000000 BITS ==========" << endl;
    LDPC_Parity_Irregular H;
    H.generate(1000000,
               "0 0.1712 0.21053 0.00273 0 0 0.00009 0.15269 0.09227 "
               "0.02802 0 0 0 0 0.01206 0 0 0 0 0 0 0 0 0 0 0 0 0 0 "
               "0.07212 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.25830",
               "0 0 0 0 0 0 0 0 0.33620 0.08883 0.57497",
               "rand",
               "0 0");  // no optimization here
    LDPC_Code C(&H);
    C.save_code("RU_1000000.it");
  }

}