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# Sparse reordering functions

This module contains all sparse reordering routines.

The sparse reordering routines describe algorithms for reordering sparse matrices. These routines do not support execution in a `hipGraph` context.

## rocsparse_csrcolor()

rocsparse_status rocsparse_scsrcolor(rocsparse_handle handle, rocsparse_int m, rocsparse_int nnz, const rocsparse_mat_descr descr, const float *csr_val, const rocsparse_int *csr_row_ptr, const rocsparse_int *csr_col_ind, const float *fraction_to_color, rocsparse_int *ncolors, rocsparse_int *coloring, rocsparse_int *reordering, rocsparse_mat_info info)

rocsparse_status rocsparse_dcsrcolor(rocsparse_handle handle, rocsparse_int m, rocsparse_int nnz, const rocsparse_mat_descr descr, const double *csr_val, const rocsparse_int *csr_row_ptr, const rocsparse_int *csr_col_ind, const double *fraction_to_color, rocsparse_int *ncolors, rocsparse_int *coloring, rocsparse_int *reordering, rocsparse_mat_info info)

rocsparse_status rocsparse_ccsrcolor(rocsparse_handle handle, rocsparse_int m, rocsparse_int nnz, const rocsparse_mat_descr descr, const rocsparse_float_complex *csr_val, const rocsparse_int *csr_row_ptr, const rocsparse_int *csr_col_ind, const float *fraction_to_color, rocsparse_int *ncolors, rocsparse_int *coloring, rocsparse_int *reordering, rocsparse_mat_info info)

rocsparse_status rocsparse_zcsrcolor(rocsparse_handle handle, rocsparse_int m, rocsparse_int nnz, const rocsparse_mat_descr descr, const rocsparse_double_complex *csr_val, const rocsparse_int *csr_row_ptr, const rocsparse_int *csr_col_ind, const double *fraction_to_color, rocsparse_int *ncolors, rocsparse_int *coloring, rocsparse_int *reordering, rocsparse_mat_info info)

  Coloring of the adjacency graph of the matrix \(A\) stored in the CSR format.

  `rocsparse_csrcolor` performs the coloring of the undirected graph represented by the (symmetric) sparsity pattern of the matrix \(A\) stored in CSR format. Graph coloring is a way of coloring the nodes of a graph such that no two adjacent nodes are of the same color. The `fraction_to_color` is a parameter to only color a given percentage of the graph nodes, the remaining uncolored nodes receive distinct new colors. The optional `reordering` array is a permutation array such that unknowns of the same color are grouped. The matrix \(A\) must be stored as a general matrix with a symmetric sparsity pattern, and if the matrix \(A\) is non-symmetric then the user is responsible to provide the symmetric part \(\frac{A+A^T}{2}\).

  Note

  This function is blocking with respect to the host.

  Note

  This routine does not support execution in a hipGraph context.

  Parameters:

    - handle – [in] handle to the rocsparse library context queue.

    - m – [in] number of rows of sparse matrix \(A\).

    - nnz – [in] number of non-zero entries of sparse matrix \(A\).

    - descr – [in] sparse matrix descriptor.

    - csr_val – [in] array of `nnz` elements of the sparse CSR matrix.

    - csr_row_ptr – [in] array of `m+1` elements that point to the start of every row of the sparse CSR matrix.

    - csr_col_ind – [in] array of `nnz` elements containing the column indices of the sparse CSR matrix.

    - fraction_to_color – [in] fraction of nodes to be colored, which should be in the interval [0.0,1.0], for example 0.8 implies that 80 percent of nodes will be colored.

    - ncolors – [out] resulting number of distinct colors.

    - coloring – [out] resulting mapping of colors.

    - reordering – [out] optional resulting reordering permutation if `reordering` is a non-null pointer.

    - info – [inout] structure that holds the information collected during the coloring algorithm.

  Return values:

    - rocsparse_status_success – the operation completed successfully.

    - rocsparse_status_invalid_handle – the library context was not initialized.

    - rocsparse_status_invalid_size – `m` or `nnz` is invalid.

    - rocsparse_status_invalid_pointer – `descr`, `csr_val`, `csr_row_ptr`, `csr_col_ind`, `fraction_to_color`, `ncolors`, `coloring` or `info` pointer is invalid.