diff --git a/src/bias/MetaD.cpp b/src/bias/MetaD.cpp
index d6a97038baae02e79f6b0e99efcff42b590cab2c..5b0995647acc4722133ce7367e56a796d6415bfc 100644
--- a/src/bias/MetaD.cpp
+++ b/src/bias/MetaD.cpp
@@ -285,6 +285,7 @@ void MetaD::registerKeywords(Keywords& keys){
   Bias::registerKeywords(keys);
   componentsAreNotOptional(keys);
   keys.addOutputComponent("bias","default","the instantaneous value of the bias potential");
+  keys.addOutputComponent("acc","ACCELERATION","the metadynamics acceleration factor");
   keys.use("ARG");
   keys.add("compulsory","SIGMA","the widths of the Gaussian hills");
   keys.add("compulsory","PACE","the frequency for hill addition");
@@ -535,10 +536,13 @@ isFirstStep(true)
 
 
   if(mw_n_>1){
+   if(walkers_mpi) error("MPI version of multiple walkers is not compatible with filesystem version of multiple walkers");
    log.printf("  %d multiple walkers active\n",mw_n_);
    log.printf("  walker id %d\n",mw_id_);
    log.printf("  reading stride %d\n",mw_rstride_);
    log.printf("  directory with hills files %s\n",mw_dir_.c_str());
+  } else {
+   if(walkers_mpi) log.printf("  Multiple walkers active using MPI communnication\n"); 
   }
 
   addComponent("bias"); componentIsNotPeriodic("bias");
@@ -584,7 +588,6 @@ isFirstStep(true)
    }
   }
 
-  if(walkers_mpi && mw_n_>1) error("MPI version of multiple walkers is not compatible with filesystem version of multiple walkers");
 
 // creating vector of ifile* for hills reading 
 // open all files at the beginning and read Gaussians if restarting
@@ -624,7 +627,7 @@ isFirstStep(true)
   log<<"  Bibliography "<<plumed.cite("Laio and Parrinello, PNAS 99, 12562 (2002)");
   if(welltemp_) log<<plumed.cite(
     "Barducci, Bussi, and Parrinello, Phys. Rev. Lett. 100, 020603 (2008)");
-  if(mw_n_>1) log<<plumed.cite(
+  if(mw_n_>1||walkers_mpi) log<<plumed.cite(
     "Raiteri, Laio, Gervasio, Micheletti, and Parrinello, J. Phys. Chem. B 110, 3533 (2006)");
   if(adaptive_!=FlexibleBin::none) log<<plumed.cite(
     "Branduardi, Bussi, and Parrinello, J. Chem. Theory Comput. 8, 2247 (2012)");
diff --git a/user-doc/tutorials/belfast-8.txt b/user-doc/tutorials/belfast-8.txt
index ee9e9e8c47edff52ededb0e6a093b84c09193d10..e71146c5dca733bf01c6d6471d90e60a46938471 100644
--- a/user-doc/tutorials/belfast-8.txt
+++ b/user-doc/tutorials/belfast-8.txt
@@ -294,10 +294,7 @@ INCLUDE FILE=plumed-common.dat
 
 METAD ...
 ARG=cv2,cv3 SIGMA=0.3,0.3 HEIGHT=0.2 PACE=100 LABEL=mw GRID_MIN=-pi,-pi GRID_MAX=pi,pi GRID_BIN=200,200
-WALKERS_N=4
-WALKERS_ID=#
-WALKERS_DIR=./
-WALKERS_RSTRIDE=500
+WALKERS_MPI
 ... METAD
 
 PRINT ARG=cv1,cv2,cv3,cv4 STRIDE=1000 FILE=COLVAR
@@ -309,6 +306,10 @@ and the simulation can be run in a similar way without doing exchanges:
 mpirun -np 4 mdrun_mpi -s topol -plumed plumed -multi 4  >& log &
 \endverbatim
 
+alternatively Multiple Walkers can be run as independent simulations sharing via the file system their own biasing potential,
+this is usefull because it provides a parallelisation that do not needs a parallel code. In this case the walkers read with
+a given frequency the gaussian deposited by the others and add them to their own.
+
 \Reference
 
 This tutorial is freely inspired to the work of Biarnes et al.