don't use at() where bounds check is already done

`std::vector::at()` does an additional bounds check eventually throwing
`std::out_of_range` exception. This is useless at places where the
bounds are already checked and/or used. In such situations one should
use `std::vector::operator[]()` which is considerably faster.

Author: torbjoernk

examples/advection_diffusion/advection_diffusion_sweeper.hpp

@@ -65,13 +65,13 @@ class AdvectionDiffusionSweeper
       double a = 1.0 / sqrt(4 * PI * nu * (t + t0));
 
       for (size_t i = 0; i < n; i++) {
-        q->at(i) = 0.0;
+        q->data()[i] = 0.0;
       }
 
       for (int ii = -2; ii < 3; ii++) {
         for (size_t i = 0; i < n; i++) {
           double x = double(i) / n - 0.5 + ii - t * v;
-          q->at(i) += a * exp(-x * x / (4 * nu * (t + t0)));
+          q->data()[i] += a * exp(-x * x / (4 * nu * (t + t0)));
         }
       }
     }
@@ -86,7 +86,7 @@ class AdvectionDiffusionSweeper
 
       double max = 0.0;
       for (size_t i = 0; i < qend->size(); i++) {
-        double d = abs(qend->at(i) - qex->at(i));
+        double d = abs(qend->data()[i] - qex->data()[i]);
         if (d > max) { max = d; }
       }
       cout << "err: " << scientific << max 
@@ -173,7 +173,7 @@ class AdvectionDiffusionSweeper
       fft.backward(q);
 
       for (size_t i = 0; i < q->size(); i++) {
-        f->at(i) = (q->at(i) - rhs->at(i)) / double(dt);
+        f->data()[i] = (q->data()[i] - rhs->data()[i]) / double(dt);
       }
     }
 };

examples/advection_diffusion/fft.hpp

@@ -59,7 +59,7 @@ class FFT
     {
       shared_ptr<workspace> wk = get_workspace(x->size());
       for (size_t i = 0; i < x->size(); i++) {
-        wk->z[i] = x->at(i);
+        wk->z[i] = x->data()[i];
       }
       fftw_execute_dft(wk->ffft, wk->wk, wk->wk);
       return wk->z;
@@ -70,7 +70,7 @@ class FFT
       shared_ptr<workspace> wk = get_workspace(x->size());
       fftw_execute_dft(wk->ifft, wk->wk, wk->wk);
       for (size_t i = 0; i < x->size(); i++) {
-        x->at(i) = real(wk->z[i]);
+        x->data()[i] = real(wk->z[i]);
       }
     }
 

examples/advection_diffusion/spectral_transfer_1d.hpp

@@ -70,7 +70,7 @@ class SpectralTransfer1D
       size_t xrat = fine->size() / crse->size();
 
       for (size_t i = 0; i < crse->size(); i++) {
-        crse->at(i) = fine->at(xrat * i);
+        crse->data()[i] = fine->at(xrat * i);
       }
     }
 

include/pfasst/encap/vector.hpp

@@ -105,7 +105,7 @@ namespace pfasst
         {
           assert(this->size() == x->size());
           for (size_t i = 0; i < this->size(); i++)
-          { this->at(i) += a * x->at(i); }
+          { this->data()[i] += a * x->data()[i]; }
         }
 
         /**
@@ -142,8 +142,10 @@ namespace pfasst
           size_t ndofs = dst[0]->size();
           for (size_t i = 0; i < ndofs; i++) {
             for (size_t n = 0; n < ndst; n++) {
+              assert(dst[n]->size() == ndofs);
               for (size_t m = 0; m < nsrc; m++) {
-                dst[n]->at(i) += a * mat(n, m) * src[m]->at(i);
+                assert(src[m]->size() == ndofs);
+                dst[n]->data()[i] += a * mat(n, m) * src[m]->data()[i];
               }
             }
           }