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//------------------------------------------------------------------------------
// GrB_Matrix_exportHint: determine sizes of arrays for GrB_Matrix_export
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2025, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
#include "transpose/GB_transpose.h"
#define GB_FREE_ALL ;
GrB_Info GrB_Matrix_exportHint // suggest the best export format
(
int *format, // export format
GrB_Matrix A // matrix to export
)
{
//--------------------------------------------------------------------------
// check inputs
//--------------------------------------------------------------------------
GB_RETURN_IF_NULL (format) ;
GB_RETURN_IF_NULL (A) ;
GB_WHERE_1 (A, "GrB_Matrix_exportHint (&format, A)") ;
// finish any pending work since this can change the sparsity of A
GB_MATRIX_WAIT (A) ;
int sparsity = GB_sparsity (A) ;
bool is_csc = A->is_csc ;
//--------------------------------------------------------------------------
// determine format that requires the least amount of modification
//--------------------------------------------------------------------------
switch (sparsity)
{
default:
case GxB_SPARSE :
// CSR and CSC formats are supported by GraphBLAS, so if the matrix
// is sparse by-row or sparse by-column, then suggest CSR or CSC.
// The matrix can be exported with no change at all.
case GxB_BITMAP :
// Bitmap is not supported as a GrB_Format. It cannot be exported
// as full, in general, so select CSR or CSC.
(*format) = is_csc ? GrB_CSC_FORMAT : GrB_CSR_FORMAT ;
break ;
case GxB_HYPERSPARSE :
// Hypersparse is not supported as a GrB_Format. Expanding a huge
// hypersparse matrix to sparse can be costly, so suggest COO.
(*format) = GrB_COO_FORMAT ;
break ;
case GxB_FULL :
// Full is not supported by GraphBLAS
(*format) = is_csc ? GrB_CSC_FORMAT : GrB_CSR_FORMAT ;
// if full was supported by GraphBLAS;
// (*format) = is_csc ? GrB_DENSE_COL_FORMAT : GrB_DENSE_ROW_FORMAT ;
break ;
}
#pragma omp flush
return (GrB_SUCCESS) ;
}
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