4.4 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.