consolidate all FFT related redundant defines and typedefs in a single header

src/lmpfftsettings.h

@@ -0,0 +1,52 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+// common FFT library related defines and compilation settings
+
+#ifndef LMP_FFT_SETTINGS_H
+#define LMP_FFT_SETTINGS_H
+
+// if user set FFTW, it means FFTW3
+
+#ifdef FFT_FFTW
+#ifndef FFT_FFTW3
+#define FFT_FFTW3
+#endif
+#endif
+
+// set strings for library info output
+
+#if defined(FFT_FFTW3)
+#define LMP_FFT_LIB "FFTW3"
+#elif defined(FFT_MKL)
+#define LMP_FFT_LIB "MKL FFT"
+#elif defined(FFT_CUFFT)
+#define LMP_FFT_LIB "cuFFT"
+#else
+#define LMP_FFT_LIB "KISS FFT"
+#endif
+
+#ifdef FFT_SINGLE
+typedef float FFT_SCALAR;
+#define FFT_PRECISION 1
+#define LMP_FFT_PREC "single"
+#define MPI_FFT_SCALAR MPI_FLOAT
+#else
+
+typedef double FFT_SCALAR;
+#define FFT_PRECISION 2
+#define LMP_FFT_PREC "double"
+#define MPI_FFT_SCALAR MPI_DOUBLE
+#endif
+
+#endif