3.4 what='scf_ke'

With this option the code makes several self-consistent calculations, in parallel on several images, varying the kinetic energy cut-off for the wavefunctions and for the charge density. In the input of pw.x one specifies the minimum values for these two cut-offs. These values are then increased in fixed intervals controlled by the following variables. The energy is then plotted as a function of the wavefunctions kinetic energy cut-off, a different curve for each value of the charge density cut-off.
The variables that control this option are:

nke        : number of kinetic energies tested for the 
             wavefunctions cut-off.
             Default: integer 5
deltake    : delta of wavefunctions kinetic energy cut-off 
             in Ry (can be either positive or negative).
             Default: real 10 Ry
nkeden     : number of kinetic energies tested for the 
             charge density cut-off.
             Default: integer 1
deltakeden : delta of charge density kinetic energy 
             cut-off in Ry (can be either positive or 
             negative).
             Default: real 100 Ry.
flkeconv   : name of the file where the data with the 
             total energy as a function of the kinetic 
             energy is written.
             Default: character(len=*) 'output_keconv.dat'
flpskeconv : name of the postscript file with the plot 
             of the total energy as a function of the 
             kinetic energy cut-off.
             Default: character(len=*) 'output_keconv'

An example for this option can be found in example10.
Number of tasks for this option: nke * nkedens.