# neigh_func_default

A SA function which computes a neighbor of a given point

## Calling Sequence

                x_neigh = neigh_func_default(x_current,T)
                x_neigh = neigh_func_default(x_current,T,param)

## Arguments

x_current

  the point for which we want to compute a neighbor

T

  the current temperature. This parameter is ignored but is there to make all the neighbour function consistent.

param

  a two columns vector. The first column correspond to the negative amplitude of variation and the second column corresponds to the positive amplitude of variation of the neighborhood. By default, the first column is a column of -0.1 and the second column is a column of 0.1.

x_neigh

  the computed neighbor

## Description

This function computes a neighbor of a given point. For example, for a continuous vector, a neighbor will be produced by adding some noise to each component of the vector. For a binary string, a neighbor will be produced by changing one bit from 0 to 1 or from 1 to 0.

## Examples

    function y = rastrigin(x)
      y = x(1)^2+x(2)^2-cos(12*x(1))-cos(18*x(2));
    endfunction

    x0          = [2 2];
    Proba_start = 0.7;
    It_Pre      = 100;
    It_extern   = 100;
    It_intern   = 1000;
    x_test = neigh_func_default(x0,%nan);

    saparams = init_param();
    saparams = add_param(saparams,'neigh_func', neigh_func_default);

    T0 = compute_initial_temp(x0, rastrigin, Proba_start, It_Pre, saparams);
    Log = %T;
    [x_opt, f_opt, sa_mean_list, sa_var_list] = optim_sa(x0, rastrigin, It_extern, It_intern, T0, Log,saparams);

    mprintf('optimal solution:\n'); disp(x_opt);
    mprintf('value of the objective function = %f\n', f_opt);

## See Also

- optim_sa
- compute_initial_temp
- temp_law_default