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2.4 Input Data Stacking

2.4 Input Data Stacking

DESCRIPTION

Input data stacking is a useful concept when performing multiple calculations. In such a case, one typically defines a set of default parameters for all calculations. However, each individual calculation may require some modification of the input data, yet it is inconvenient if such a change would affect the input data for other subsequent calculations. This inconvenience can be prevented by using the input data stacking and to this end the PWTK provides the input_pushpop command. The concept is illustrated below:

    #------------------------------------------------------------------------
    import input-data.pwtk    
    # let's label the input-data at this point as (#0)

    # prepare and run the 1st calculation 
    input_pushpop {
       # input data has been pushed on the stack;
       # at this point the input data is the same as in (#0)

       ... modify input data for this calculation (#1)
       ... perform the 1st calculation
    }
    # the modification of input data made inside the above input_pushpop { ... }
    # was popped away; at this point the input data is the same as in (#0)

    # prepare and run the 2nd calculation
    input_pushpop {
       # input data still the same as in (#0)

       ... modify input data for this calculation (#2)
       ... perform the 2nd calculation

       # prepare and run the 3rd calculation
       input_pushpop {
          # input data is the same as in (#2)

          ... modify input data for this calculation (#3)
          ... perform the 3rd calculation
       }

      # at this point the input data is the same as in (#2)
    }

    # at this point the input data is again the same as in (#0)

    ... perform further calculations
    #-----------------------------------------------------------------------

EXAMPLE

And here is a simple actual example that consists of three scans: (i) scan over cutoff energy, (ii) scan over k-points, and (iii) scan over A-lattice parameter. Note that due to use of input_pushpop { ... } none of the test affects the input data for subseuqent tests.

     # pw.x input data are stored in "input-data.pwtk file
     import input-data.pwtk

     # scan the cutoff energy
     input_pushpop {
        foreach e [seq 20.0 5.0 50.0] {
           SYSTEM "ecutwfc = $e, ecutrho = 8*$e"
           runPW scf.ecut$e.in
        }
     }

     # scan the k-points
     input_pushpop {
        foreach k {2 4 6 8 10 12} {
           K_POINTS automatic "$k $k $k   1 1 1"
           runPW scf.k$k.in
        }
     }

    # scan the lattice-parameter
    input_pushpop {
        foreach alat [seq 9.0 0.2 10.8] {
           SYSTEM " celldm(1) = $alat "
           runPW scf.alat$alat.in
        }
    }

TABLE OF CONTENTS

2.4 Input Data Stacking