LibSVM Question. Regarding C and gamma parameters

I am currently trying to run LibSVM located here: https://www.csie.ntu.edu.tw/~cjlin/libsvm

I only have access to MATLAB 2011b. When I try to run the example data file (heartscale) included with the LibSVM package with different C and gamma values I get the same accuracy results. This happens for other data sets as well. I build a for loop and loop through the different C and gamma values and the accuracy %'s do not change. I am doing this to find the best C and gamma to use for the data set (cross-validation) as recommended in the documentation "A Practical Guide to Support Vector Classification" located on the above website. When I look at the accuracy_mat that I build below, the values are all the same. Even the outputs from svmpredict are the same.

I have read through the documentation multiple times and looked at the FAQ on the website. I am stumped. Please help.

    [heart_scale_label, heart_scale_inst] = libsvmread('heartscale');
    C = {'2^-5','2^-3','2^-1'}; 
    g = {'2^-15','2^-3','2^-1'}; 
    accuracy_mat = zeros(length(g),length(c));
    data_num = length(heart_scale_inst(:,1));
    t = zeros(data_num,1);
    for i=1:length(g)
        for j=1:length(C)
            c_train_inputs = ['-c ', C{j}];
            g_train_inputs = ['-g ', g{i}];

            c_and_g_inputs = [c_train_inputs, g_train_inputs];
            model = svmtrain(heart_scale_label,heart_scale_inst,[c_and_g_inputs, '-b 1']);
            [predict_label, accuracy, prob_estimates] = svmpredict(heart_scale_label, heart_scale_inst, model, '-b 1');
            accuracy_mat(i,j) = max(accuracy);
      end
  end