fix comments.

Former-commit-id: 6ebc43a797faeab64f73ae9665142dff5e3a0633

src/debug.h

@@ -21,3 +21,4 @@
 
 
 void printParticle(struct part *parts, long long int i, int N);
+void printParticle_single ( struct part *p );

src/engine.c

@@ -506,8 +506,7 @@ void engine_step ( struct engine *e , int sort_queues ) {
         
     // for(k=0; k<10; ++k)
     //   printParticle(parts, k);
-    // printParticle( parts , 432626 );
-    // printParticle( parts , 432628 );
+    // printParticle( e->s->parts , 382557 , e->s->nr_parts );
  
     /* Prepare the space. */
     engine_prepare( e );
@@ -538,7 +537,7 @@ void engine_step ( struct engine *e , int sort_queues ) {
             
     /* Stop the clock. */
     TIMER_TOC(timer_runners);
-    
+
     // engine_single_force( e->s->dim , 6178 , e->s->parts , e->s->nr_parts , e->s->periodic );
     
     // for(k=0; k<10; ++k)
@@ -560,7 +559,7 @@ void engine_step ( struct engine *e , int sort_queues ) {
         }
     
     e->dt_min = dt_min;
-    // printParticle( parts , 432626 );
+    // printParticle( e->s->parts , 382557 , e->s->nr_parts );
     printf( "engine_step: dt_min/dt_max is %e/%e.\n" , dt_min , dt_max ); fflush(stdout);
     printf( "engine_step: etot is %e (ekin=%e, epot=%e).\n" , ekin+epot , ekin , epot ); fflush(stdout);
     printf( "engine_step: total momentum is [ %e , %e , %e ].\n" , mom[0] , mom[1] , mom[2] ); fflush(stdout);

src/part.h

@@ -119,7 +119,7 @@ struct part {
     
             /* Sound speed */
             float c;
-
+            
             } force;
             
         };

src/runner.c

@@ -382,18 +382,21 @@ void runner_doghost ( struct runner *r , struct cell *c ) {
                 wcount = ( p->density.wcount + kernel_root ) * ( 4.0f / 3.0 * M_PI * kernel_gamma3 );
                 wcount_dh = p->density.wcount_dh * ih * ( 4.0f / 3.0 * M_PI * kernel_gamma3 );
                     
-                /* Compute the smoothing length update (Newton step). */
+                /* If no derivative, double the smoothing length. */
                 if ( wcount_dh == 0.0f )
                     h_corr = p->h;
+                    
+                /* Otherwise, compute the smoothing length update (Newton step). */
                 else {
                     h_corr = ( const_nwneigh - wcount ) / wcount_dh;
 
                     /* Truncate to the range [ -p->h/2 , p->h ]. */
                     h_corr = fminf( h_corr , h );
                     h_corr = fmaxf( h_corr , -h/2 );
+                    
                     }
                 
-                /* Apply the correction to p->h. */
+                /* Apply the correction to p->h and to the compact part. */
                 p->h += h_corr;
                 cp->h = p->h;