spy.hpp

// Copyright (c) Sleipnir contributors
 
#pragma once
 
#ifndef SLEIPNIR_DISABLE_DIAGNOSTICS
 
#include <stdint.h>
 
#include <bit>
#include <fstream>
#include <ios>
#include <string>
#include <string_view>
 
#include <Eigen/SparseCore>
 
namespace slp {
 
template <typename Scalar>
class Spy {
 public:
  Spy(std::string_view filename, std::string_view title,
      std::string_view row_label, std::string_view col_label, int rows,
      int cols)
      : m_file{std::string{filename}, std::ios::binary} {
    // Write title
    write32le(title.size());
    m_file.write(title.data(), title.size());
 
    // Write row label
    write32le(row_label.size());
    m_file.write(row_label.data(), row_label.size());
 
    // Write column label
    write32le(col_label.size());
    m_file.write(col_label.data(), col_label.size());
 
    // Write row and column counts
    write32le(rows);
    write32le(cols);
  }
 
  void add(const Eigen::SparseMatrix<Scalar>& mat) {
    // Write number of coordinates
    write32le(mat.nonZeros());
 
    // Write coordinates
    for (int k = 0; k < mat.outerSize(); ++k) {
      for (typename Eigen::SparseMatrix<Scalar>::InnerIterator it{mat, k}; it;
           ++it) {
        write32le(it.row());
        write32le(it.col());
        if (it.value() > Scalar(0)) {
          m_file << '+';
        } else if (it.value() < Scalar(0)) {
          m_file << '-';
        } else {
          m_file << '0';
        }
      }
    }
  }
 
 private:
  std::ofstream m_file;
 
  void write32le(int32_t num) {
    if constexpr (std::endian::native != std::endian::little) {
      num = std::byteswap(num);
    }
    m_file.write(reinterpret_cast<char*>(&num), sizeof(num));
  }
};
 
}  // namespace slp
 
#endif