mtx_loader.h

#pragma once
#include <cstdint>
#include <string>
#include <vector>

namespace sbfft {

// Binary sparse matrix in CSR form. Values are implicit 1 (any numeric
// values in the .mtx are discarded). After load, the matrix is
// symmetrically expanded if the .mtx had `symmetric` qualifier, sorted by
// (row, col), and deduplicated.
struct CsrBinary {
    int N = 0;
    int64_t nnz = 0;
    std::vector<int> rowPtr;     // length N+1
    std::vector<int> colIdx;     // length nnz
};

// Loads `path` (a .mtx file). On first load, parses the .mtx and writes a
// `path + ".bin"` cache; on subsequent loads, reads the cache directly.
CsrBinary load_mtx(const std::string& path, bool verbose = true);

// Statistics helper (max / min / mean nonzeros per row, empty rows).
struct RowStats {
    int min_k;
    int max_k;
    double mean_k;
    int empty_rows;
};
RowStats compute_row_stats(const CsrBinary& csr);

} // namespace sbfft