Spy.hpp

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// Copyright (c) Sleipnir contributors
 
#pragma once
 
#include <stdint.h>
 
#include <bit>
#include <fstream>
#include <string>
#include <string_view>
 
#include <Eigen/SparseCore>
 
#include "sleipnir/util/SymbolExports.hpp"
 
namespace sleipnir {
 
class SLEIPNIR_DLLEXPORT Spy {
 public:
  Spy(std::string_view filename, std::string_view title,
      std::string_view rowLabel, std::string_view colLabel, 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(rowLabel.size());
    m_file.write(rowLabel.data(), rowLabel.size());
 
    // Write column label
    Write32le(colLabel.size());
    m_file.write(colLabel.data(), colLabel.size());
 
    // Write row and column counts
    Write32le(rows);
    Write32le(cols);
  }
 
  void Add(const Eigen::SparseMatrix<double>& mat) {
    // Write number of coordinates
    Write32le(mat.nonZeros());
 
    // Write coordinates
    for (int k = 0; k < mat.outerSize(); ++k) {
      for (Eigen::SparseMatrix<double>::InnerIterator it{mat, k}; it; ++it) {
        Write32le(it.row());
        Write32le(it.col());
        if (it.value() > 0.0) {
          m_file << '+';
        } else if (it.value() < 0.0) {
          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 sleipnir