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cannam@167:When creating plans in FFTW, a number of constants are used to specify
cannam@167: options, such as FFTW_MEASURE or FFTW_ESTIMATE. The
cannam@167: same constants must be used with the wrapper routines, but of course the
cannam@167: C header files where the constants are defined can’t be incorporated
cannam@167: directly into Fortran code.
cannam@167:
Instead, we have placed Fortran equivalents of the FFTW constant
cannam@167: definitions in the file fftw3.f, which can be found in the same
cannam@167: directory as fftw3.h. If your Fortran compiler supports a
cannam@167: preprocessor of some sort, you should be able to include or
cannam@167: #include this file; otherwise, you can paste it directly into
cannam@167: your code.
cannam@167:
In C, you combine different flags (like FFTW_PRESERVE_INPUT and
cannam@167: FFTW_MEASURE) using the ‘|’ operator; in Fortran
cannam@167: you should just use ‘+’. (Take care not to add in the
cannam@167: same flag more than once, though. Alternatively, you can use the
cannam@167: ior intrinsic function standardized in Fortran 95.)
cannam@167: