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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 cannam@95: fftw_export_wisdom_to_filename and cannam@95: fftw_wisdom_from_filename. The only trick is that these cannam@95: require you to pass a C string, which is an array of type cannam@95: CHARACTER(C_CHAR) that is terminated by C_NULL_CHAR. cannam@95: You can call them like this: cannam@95: cannam@95:

       integer(C_INT) :: ret
cannam@95:        ret = fftw_export_wisdom_to_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
cannam@95:        if (ret .eq. 0) stop 'error exporting wisdom to file'
cannam@95:        ret = fftw_import_wisdom_from_filename(C_CHAR_'my_wisdom.dat' // C_NULL_CHAR)
cannam@95:        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 cannam@95: literal string is of kind C_CHAR, and we null-terminate the cannam@95: string by appending ‘// C_NULL_CHAR’. These functions return an cannam@95: integer(C_INT) (ret) which is 0 if an error cannam@95: occurred during export/import and nonzero otherwise. cannam@95: cannam@95:

It is also possible to use the lower-level routines cannam@95: fftw_export_wisdom_to_file and cannam@95: fftw_import_wisdom_from_file, which accept parameters of the C cannam@95: type FILE*, expressed in Fortran as type(C_PTR). cannam@95: However, you are then responsible for creating the FILE* cannam@95: yourself. You can do this by using iso_c_binding to define cannam@95: Fortran intefaces for the C library functions fopen and cannam@95: fclose, which is a bit strange in Fortran but workable. cannam@95: cannam@95: cannam@95: cannam@95: