Undefined function 'caffe_'for input arguments of type'char'

When I run code in matlab2014a, there is always an error:

Undefined function 'caffe_'for input arguments of type'char'.
Error in net_surgery(line10)
caffe_('reset');

The PC resource: ubuntu 14.04

and I have added the matcaffe path to matlab. The code as follows:

if exist(fullfile(caffe_root,'/matlab/+caffe/private'),'dir')
    addpath(fullfile(caffe_root,'/matlab/+caffe/private'));
else
    warnning('Please install Caffe in %s', caffe_root);
end

what can I do for it? Someone can help me? Thanks very much.