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Short helpfile for action DRR
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The following arguments are compulsory: 

                    TAU - ( default=0.5 ) specifies relaxation time on each of 
                          variables are, similar to extended Time Constant in Colvars 
               FRICTION - ( default=8.0 ) add a friction to the variable, similar to 
                          extended Langevin Damping in Colvars 
               GRID_MIN - the lower bounds for the grid (GRID_BIN or GRID_SPACING 
                          should be specified) 
               GRID_MAX - the upper bounds for the grid (GRID_BIN or GRID_SPACING 
                          should be specified) 
         REFLECTINGWALL - ( default=0 ) whether add reflecting walls for each CV at 
                          GRID_MIN and GRID_MAX. Setting non-zero values will enable this 
                          feature 
            FULLSAMPLES - ( default=500 ) number of samples in a bin prior to 
                          application of the ABF 
              MAXFACTOR - ( default=1.0 ) maximum scaling factor of biasing force 
             OUTPUTFREQ - write results to a file every N steps 

In addition you may use the following options: 

  NUMERICAL_DERIVATIVES - ( default=off ) calculate the derivatives for these 
                          quantities numerically 
                 NOCZAR - ( default=off ) disable the CZAR estimator 
                     UI - ( default=off ) enable the umbrella integration estimator 
                 NOBIAS - ( default=off ) DO NOT apply bias forces. 
             TEXTOUTPUT - ( default=off ) use text output for grad and count files 
                          instead of boost::serialization binary output 
      MERGEHISTORYFILES - ( default=off ) output all historic results to a single 
                          file rather than multiple .drrstate files. This option is 
                          effective only when textOutput is on. 
                    ARG - the input for this action is the scalar output from one or 
                          more other actions. The particular scalars that you will use are 
                          referenced using the label of the action. If the label appears on its 
                          own then it is assumed that the Action calculates a single 
                          scalar value. The value of this scalar is thus used as the input 
                          to this new action. If * or *.* appears the scalars calculated 
                          by all the proceeding actions in the input file are taken. 
                          Some actions have multi-component outputs and each component of 
                          the output has a specific label. For example a \ref DISTANCE 
                          action labelled dist may have three components x, y and z. To take 
                          just the x component you should use dist.x, if you wish to take 
                          all three components then use dist.*.More information on the 
                          referencing of Actions can be found in the section of the manual on the 
                          PLUMED \ref Syntax. Scalar values can also be referenced using 
                          POSIX regular expressions as detailed in the section on \ref 
                          Regex. To use this feature you you must compile PLUMED with the 
                          appropriate flag. You can use multiple instances of this keyword i.e. 
                          ARG1, ARG2, ARG3... 
                  KAPPA - specifies that the restraint is harmonic and what the 
                          values of the force constants on each of the variables are 
                          (default to \f$k_BT\f$/(GRID_SPACING)^2) 
               GRID_BIN - the number of bins for the grid 
           GRID_SPACING - the approximate grid spacing (to be used as an alternative 
                          or together with GRID_BIN) 
              ZGRID_MIN - the lower bounds for the grid (ZGRID_BIN or ZGRID_SPACING 
                          should be specified) 
              ZGRID_MAX - the upper bounds for the grid (ZGRID_BIN or ZGRID_SPACING 
                          should be specified) 
              ZGRID_BIN - the number of bins for the grid 
          ZGRID_SPACING - the approximate grid spacing (to be used as an alternative 
                          or together with ZGRID_BIN) 
         EXTERNAL_FORCE - use forces from other action instead of internal spring 
                          force, this disable the extended system! 
          EXTERNAL_FICT - position of external fictitious particles, useful for 
                          UIESTIMATOR 
            HISTORYFREQ - save history to a file every N steps 
        UIRESTARTPREFIX - specify the restart files for umbrella integration 
           OUTPUTPREFIX - specify the output prefix (default to the label name) 
                   TEMP - the system temperature - needed when FRICTION is present. 
                          If not provided will be taken from MD code (if available) 
                EXTTEMP - the temperature of extended variables (default to system 
                          temperature) 
              DRR_RFILE - specifies the restart file (.drrstate file) 


