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37 * Implements function to compute many autocorrelation functions
39 * \author David van der Spoel <david.vanderspoel@icm.uu.se>
40 * \ingroup module_correlationfunctions
44 #include "manyautocorrelation.h"
48 #include "gromacs/fft/fft.h"
49 #include "gromacs/utility/exceptions.h"
50 #include "gromacs/utility/gmxomp.h"
52 int many_auto_correl(std::vector<std::vector<real>>* c)
54 size_t nfunc = (*c).size();
57 GMX_THROW(gmx::InconsistentInputError("Empty array of vectors supplied"));
59 size_t ndata = (*c)[0].size();
62 GMX_THROW(gmx::InconsistentInputError("Empty vector supplied"));
65 for (size_t i = 1; i < nfunc; i++)
67 if ((*c)[i].size() != ndata)
72 "Vectors of different lengths supplied (%d %d)",
73 static_cast<int>((*c)[i].size()),
74 static_cast<int>(ndata));
75 GMX_THROW(gmx::InconsistentInputError(buf));
79 // Add buffer size to the arrays.
80 size_t nfft = (3 * ndata / 2) + 1;
81 // Pad arrays with zeros
91 std::vector<real> in, out;
93 int nthreads = gmx_omp_get_max_threads();
94 int thread_id = gmx_omp_get_thread_num();
95 int i0 = (thread_id * nfunc) / nthreads;
96 int i1 = std::min(nfunc, ((thread_id + 1) * nfunc) / nthreads);
98 gmx_fft_init_1d(&fft1, nfft, GMX_FFT_FLAG_CONSERVATIVE);
99 /* Allocate temporary arrays */
100 in.resize(2 * nfft, 0);
101 out.resize(2 * nfft, 0);
102 for (int i = i0; (i < i1); i++)
104 for (size_t j = 0; j < ndata; j++)
106 in[2 * j + 0] = (*c)[i][j];
109 gmx_fft_1d(fft1, GMX_FFT_BACKWARD, in.data(), out.data());
110 for (size_t j = 0; j < nfft; j++)
113 (out[2 * j + 0] * out[2 * j + 0] + out[2 * j + 1] * out[2 * j + 1]) / nfft;
116 gmx_fft_1d(fft1, GMX_FFT_FORWARD, in.data(), out.data());
117 for (size_t j = 0; (j < nfft); j++)
119 (*c)[i][j] = out[2 * j + 0];
122 /* Free the memory */
123 gmx_fft_destroy(fft1);
125 GMX_CATCH_ALL_AND_EXIT_WITH_FATAL_ERROR