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7.6.1 Wisdom File Export/Import from Fortran

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The easiest way to export and import wisdom is to do so using Chris@19: fftw_export_wisdom_to_filename and Chris@19: fftw_wisdom_from_filename. The only trick is that these Chris@19: require you to pass a C string, which is an array of type Chris@19: CHARACTER(C_CHAR) that is terminated by C_NULL_CHAR. Chris@19: You can call them like this: Chris@19: Chris@19:

       integer(C_INT) :: ret
Chris@19:        ret = fftw_export_wisdom_to_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
Chris@19:        if (ret .eq. 0) stop 'error exporting wisdom to file'
Chris@19:        ret = fftw_import_wisdom_from_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
Chris@19:        if (ret .eq. 0) stop 'error importing wisdom from file'
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Note that prepending ‘C_CHAR_’ is needed to specify that the Chris@19: literal string is of kind C_CHAR, and we null-terminate the Chris@19: string by appending ‘// C_NULL_CHAR’. These functions return an Chris@19: integer(C_INT) (ret) which is 0 if an error Chris@19: occurred during export/import and nonzero otherwise. Chris@19: Chris@19:

It is also possible to use the lower-level routines Chris@19: fftw_export_wisdom_to_file and Chris@19: fftw_import_wisdom_from_file, which accept parameters of the C Chris@19: type FILE*, expressed in Fortran as type(C_PTR). Chris@19: However, you are then responsible for creating the FILE* Chris@19: yourself. You can do this by using iso_c_binding to define Chris@19: Fortran intefaces for the C library functions fopen and Chris@19: fclose, which is a bit strange in Fortran but workable. Chris@19: Chris@19: Chris@19: Chris@19: