Generic functions

Apart from Trigonometric functions, there are also generic functions that can be used in any Numerical P System simulated in Pep. The generic functions are:

• sqrt
• abs
• log
• log10
• log2
• min
• max

Two parameter functions, such as min and max are called using the following syntax function( (parameter_1) (parameter_2) ).

An example Numerical P System that uses the previous list of functions can be found in input_files/input_generic_func.pep and is also shown below:

num_ps = {
    # membrane names (labels)
    H = {m1, m2};

    # test generic functions (Matlab/Octave names):
    #   sqrt, abs, log, log10, log2. min, max
    structure = [m1 [m2 ]m2 ]m1;
    #structure = [m1
            #[m2 ]m2
        #]m1;

    # membrane 1
    m1 = {
        var = {rez_1};
        # rez = 27.935 (3.3166 + 12 + 2.5649 + 1.1461 + 3.9069 + 5)
        # two variable functions like min require variables to be defined within brackets
        pr = {sqrt(11) + abs(0 - 12) + log(13) + log10(14) + log2(15) + min((5) (10)) + rez_1 * 0 -> 1|rez_1};
        var0 = (0);
    };

    m2 = {
        var = {rez_2};
        # rez = 30.480 (4.6904 + 4 + 2.9444 + 0.84510 + 8 + 10)
        # two variable functions like max require variables to be defined within brackets
        pr = {sqrt(11 * 2) + abs((0 - 12) / 3) + log(13 + 6) + log10(14 - 7) + log2(2 ^ 8) + max((5) (10)) + rez_2 * 0  -> 1|rez_2};
        var0 = (0);
    };
}

The output of the Numerical P System, for a single execution step was obtained after executing the following command:

./pep.py input_files/input_generic_func.pep -n 1

and offers the following output:

INFO     reading input file
INFO     building NumericalPsystem
INFO     building membrane list
INFO     building membrane structure
INFO     building Membrane
INFO     building variable list
INFO     building Program
INFO     building production function
INFO     building distribution rule
INFO     building var0 list
INFO     building Membrane
INFO     building variable list
INFO     building Program
INFO     building production function
INFO     building distribution rule
INFO     building var0 list
num_ps = {
    m1:
        var = { rez_1: 0.00, }
        E = {}
        pr_0 = { sqrt ( 11 ) + abs ( 0 - 12 ) + log ( 13 ) + log10 ( 14 ) + log2 ( 15 ) + min ( ( 5 ) ( 10 ) ) + rez_1 * 0  ->  1|rez_1 }
    m2:
        var = { rez_2: 0.00, }
        E = {}
        pr_0 = { sqrt ( 11 * 2 ) + abs ( ( 0 - 12 ) / 3 ) + log ( 13 + 6 ) + log10 ( 14 - 7 ) + log2 ( 2 ^ 8 ) + max ( ( 5 ) ( 10 ) ) + rez_2 * 0  ->  1|rez_2 }
}

INFO     Starting simulation step 1
INFO     Simulation step finished succesfully
num_ps = {
  m1:
    var = { rez_1: 27.93, }
    E = {}
  m2:
    var = { rez_2: 30.48, }
    E = {}
}

The P object values that are printed by the simulator are not always precisely equal to those obtained in other mathematical software. The reason is that during the printing of each value, these are rounded to the nearest 2 digit value. The internal calculations are always done using double precision floating point values.