add back autocorrelation functionality

bfps/cpp/fluid_solver_base.cpp

@@ -46,6 +46,26 @@ void fluid_solver_base<rnumber>::clean_up_real_space(rnumber *a, int howmany)
         std::fill_n(a+rindex+this->rd->subsizes[2]*howmany, 2*howmany, 0.0);
 }
 
+template <class rnumber>
+rnumber fluid_solver_base<rnumber>::autocorrel(cnumber *a)
+{
+    double *spec = fftw_alloc_real(this->nshells*9);
+    double sum_local, sum;
+    this->cospectrum(a, a, spec);
+    sum_local = 0.0;
+    for (int n = 0; n < this->nshells; n++)
+        sum_local += spec[n*9] + spec[n*9 + 4] + spec[n*9 + 8];
+    fftw_free(spec);
+    MPI_Allreduce(
+            &sum_local,
+            &sum,
+            1,
+            MPI_DOUBLE,
+            MPI_SUM,
+            this->cd->comm);
+    return sum;
+}
+
 template <class rnumber>
 void fluid_solver_base<rnumber>::cospectrum(cnumber *a, cnumber *b, double *spec)
 {

bfps/cpp/fluid_solver_base.hpp

@@ -83,6 +83,7 @@ class fluid_solver_base
         void clean_up_real_space(rnumber *a, int howmany);
         void cospectrum(cnumber *a, cnumber *b, double *spec);
         void cospectrum(cnumber *a, cnumber *b, double *spec, const double k2exponent);
+        rnumber autocorrel(cnumber *a);
         void compute_rspace_stats(rnumber *a,
                                   double *moments,
                                   ptrdiff_t *hist,

bfps/fluid_base.py

@@ -126,7 +126,7 @@ class fluid_particle_base(bfps.code):
                                   'local_time_difference = ((unsigned int)(time1 - time0))/((double)CLOCKS_PER_SEC);\n' +
                                   'time_difference = 0.0;\n' +
                                   'MPI_Allreduce(&local_time_difference, &time_difference, ' +
-                                      '1, MPI_DOUBLE, MPI_SUM, fs->rd->comm);\n' +
+                                      '1, MPI_DOUBLE, MPI_SUM, MPI_COMM_WORLD);\n' +
                                   'if (myrank == 0) std::cout << "iteration " ' +
                                       '<< iteration << " took " ' +
                                       '<< time_difference/nprocs << " seconds" << std::endl;\n' +

bfps/fluid_resize.py

@@ -70,15 +70,15 @@ class fluid_resize(bfps.fluid_base.fluid_particle_base):
                 fs1->iteration = 0;
                 fs0->read('v', 'c');
                 double a, b;
-                a = 0.5*fs0->correl_vec(fs0->cvelocity, fs0->cvelocity);
-                b = 0.5*fs0->correl_vec(fs0->cvorticity, fs0->cvorticity);
+                a = 0.5*fs0->autocorrel(fs0->cvelocity);
+                b = 0.5*fs0->autocorrel(fs0->cvorticity);
                 DEBUG_MSG("old field %d %g %g\\n", fs0->iteration, a, b);
                 copy_complex_array<{0}>(fs0->cd, fs0->cvorticity,
                                         fs1->cd, fs1->cvorticity,
                                         3);
                 fs1->write('v', 'c');
-                a = 0.5*fs1->correl_vec(fs1->cvelocity, fs1->cvelocity);
-                b = 0.5*fs1->correl_vec(fs1->cvorticity, fs1->cvorticity);
+                a = 0.5*fs1->autocorrel(fs1->cvelocity);
+                b = 0.5*fs1->autocorrel(fs1->cvorticity);
                 DEBUG_MSG("new field %d %g %g\\n", fs1->iteration, a, b);
                 niter_todo = 0;
                 //endcpp