r.mapcalc
Raster map calculator. 
Raster (r.*)
ParameterMultipleInput|maps|Raster maps used in the calculator|3|True
ParameterString|expression|Expression to evaluate. Syntax e.g. `raster_out=raster1+raster2`. Use original filenames, without extension|None|True|True
ParameterFile|file|File containing expression(s) to evaluate (same rule for raster names than above)|True
ParameterString|seed|Integer seed for rand() function|None|False|True
*ParameterBoolean|-s|Generate random seed (result is non-deterministic)|False
OutputDirectory|output_dir|Results Directory