diff --git a/src/engine.c b/src/engine.c
index 3437a495efb662ebd7cad1970f2132d8481e93e8..2e70d45a1ae50252077fe4e411000bdebf89ba7a 100644
--- a/src/engine.c
+++ b/src/engine.c
@@ -1618,7 +1618,7 @@ void engine_barrier(struct engine *e, int tid) {
 }
 
 /**
- * @brief Mapping function to collect the data from the second kick.
+ * @brief Mapping function to collect the data from the kick.
  */
 
 void engine_collect_kick(struct cell *c) {
@@ -1666,120 +1666,9 @@ void engine_collect_kick(struct cell *c) {
   c->ang[2] = ang[2];
 }
 
-/**
- * @brief Compute the force on a single particle brute-force.
- */
 
-// void engine_single_density ( double *dim , long long int pid , struct part
-// *__restrict__ parts , int N , int periodic ) {
-//
-//     int i, k;
-//     double r2, dx[3];
-//     float fdx[3], ih;
-//     struct part p;
-//
-//     /* Find "our" part. */
-//     for ( k = 0 ; k < N && parts[k].id != pid ; k++ );
-//     if ( k == N )
-//         error( "Part not found." );
-//     p = parts[k];
-//
-//     /* Clear accumulators. */
-//     ih = 1.0f / p.h;
-//     p.rho = 0.0f; p.rho_dh = 0.0f;
-//     p.density.wcount = 0.0f; p.density.wcount_dh = 0.0f;
-//     p.density.div_v = 0.0;
-//     for ( k=0 ; k < 3 ; k++)
-//         p.density.curl_v[k] = 0.0;
-//
-//     /* Loop over all particle pairs (force). */
-//     for ( k = 0 ; k < N ; k++ ) {
-//         if ( parts[k].id == p.id )
-//             continue;
-//         for ( i = 0 ; i < 3 ; i++ ) {
-//             dx[i] = p.x[i] - parts[k].x[i];
-//             if ( periodic ) {
-//                 if ( dx[i] < -dim[i]/2 )
-//                     dx[i] += dim[i];
-//                 else if ( dx[i] > dim[i]/2 )
-//                     dx[i] -= dim[i];
-//                 }
-//             fdx[i] = dx[i];
-//             }
-//         r2 = fdx[0]*fdx[0] + fdx[1]*fdx[1] + fdx[2]*fdx[2];
-//         if ( r2 < p.h*p.h*kernel_gamma2 ) {
-//             runner_iact_nonsym_density( r2 , fdx , p.h , parts[k].h , &p ,
-// &parts[k] );
-//             }
-//         }
-//
-//     /* Dump the result. */
-//     p.rho = ih * ih * ih * ( p.rho + p.mass*kernel_root );
-//     p.rho_dh = p.rho_dh * ih * ih * ih * ih;
-//     p.density.wcount = ( p.density.wcount + kernel_root ) * ( 4.0f / 3.0 *
-// M_PI * kernel_gamma3 );
-//     message( "part %lli (h=%e) has wcount=%e, rho=%e, rho_dh=%e." , p.id ,
-// p.h , p.density.wcount , p.rho , p.rho_dh );
-//     fflush(stdout);
-//
-//     }
-
-// void engine_single_force ( double *dim , long long int pid , struct part
-// *__restrict__ parts , int N , int periodic ) {
-//
-//     int i, k;
-//     double r2, dx[3];
-//     float fdx[3];
-//     struct part p;
-//
-//     /* Find "our" part. */
-//     for ( k = 0 ; k < N && parts[k].id != pid ; k++ );
-//     if ( k == N )
-//         error( "Part not found." );
-//     p = parts[k];
-//
-//     /* Clear accumulators. */
-//     p.a[0] = 0.0f; p.a[1] = 0.0f; p.a[2] = 0.0f;
-//     p.force.u_dt = 0.0f; p.force.h_dt = 0.0f; p.force.v_sig = 0.0f;
-//
-//     /* Loop over all particle pairs (force). */
-//     for ( k = 0 ; k < N ; k++ ) {
-//     // for ( k = N-1 ; k >= 0 ; k-- ) {
-//         if ( parts[k].id == p.id )
-//             continue;
-//         for ( i = 0 ; i < 3 ; i++ ) {
-//             dx[i] = p.x[i] - parts[k].x[i];
-//             if ( periodic ) {
-//                 if ( dx[i] < -dim[i]/2 )
-//                     dx[i] += dim[i];
-//                 else if ( dx[i] > dim[i]/2 )
-//                     dx[i] -= dim[i];
-//                 }
-//             fdx[i] = dx[i];
-//             }
-//         r2 = fdx[0]*fdx[0] + fdx[1]*fdx[1] + fdx[2]*fdx[2];
-//         if ( r2 < p.h*p.h*kernel_gamma2 || r2 <
-// parts[k].h*parts[k].h*kernel_gamma2 ) {
-//             p.a[0] = 0.0f; p.a[1] = 0.0f; p.a[2] = 0.0f;
-//             p.force.u_dt = 0.0f; p.force.h_dt = 0.0f; p.force.v_sig = 0.0f;
-//             runner_iact_nonsym_force( r2 , fdx , p.h , parts[k].h , &p ,
-// &parts[k] );
-//             double dvdr = ( (p.v[0]-parts[k].v[0])*fdx[0] +
-// (p.v[1]-parts[k].v[1])*fdx[1] + (p.v[2]-parts[k].v[2])*fdx[2] ) / sqrt(r2);
-//             message( "part %lli and %lli interact (r=%.3e,dvdr=%.3e) with
-// a=[%.3e,%.3e,%.3e], dudt=%.3e." ,
-//                 p.id , parts[k].id , sqrt(r2) , dvdr , p.a[0] , p.a[1],
-// p.a[2] , p.force.u_dt );
-//             }
-//         }
-//
-//     /* Dump the result. */
-//     // message( "part %lli (h=%e) has a=[%.3e,%.3e,%.3e], udt=%e." , p.id ,
-// p.h , p.a[0] , p.a[1] , p.a[2] , p.force.u_dt );
-//     fflush(stdout);
-//
-//     }
 
+ 
 /**
  * @brief Launch the runners.
  *