From 9ab5f71d4190700a8c96089ab79f61b5bc8eda63 Mon Sep 17 00:00:00 2001
From: Giovanni Bussi <giovanni.bussi@gmail.com>
Date: Fri, 24 Jun 2016 14:26:30 +0200
Subject: [PATCH] added notes on metad

---
 user-doc/Performances.txt | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/user-doc/Performances.txt b/user-doc/Performances.txt
index 8d85ba817..dbdce7631 100644
--- a/user-doc/Performances.txt
+++ b/user-doc/Performances.txt
@@ -68,8 +68,25 @@ mpiexec -np 4 gmx_mpi mdrun -nb gpu -ntomp 1 -pin on -gpu_id 0011
 
 \page Metadyn Metadynamics
 
-TO DO
-
+Metadynamics can be sped up significantly using grids,
+which are activated setting the GRID_MIN and GRID_MAX keywords of \ref METAD.
+This makes addition of a hill to the list a bit slower (since
+the Gaussian has to be evaluated for many grid points)
+but the evaluation of the potential very fast. Since
+the latter is usually done every few hundred steps, whereas the former
+typically ad every step, using grids will make the simulation
+much faster.
+
+Notice that when restarting a simulation the history is read  by default
+from a file and hills are added again to the grid.
+This allows one to change the grid boundaries upon restart. However,
+the first step after restart is usually very slow.
+Since PLUMED 2.3 you can also store the grid on a file
+and read it upon restart. This can be particularly
+useful if you perform many restarts and if your hills file has
+become very large.
+
+For the precise syntax, see \ref METAD
 
 \page MTS Multiple time stepping
 
-- 
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