option to run demo in CPU mode

rcnn_demo.m

-function rcnn_demo()
+function rcnn_demo(use_gpu)
+% rcnn_demo(use_gpu)
+%   Run the R-CNN demo on a test image. Set use_gpu = false to run
+%   in CPU mode. (GPU mode is the default.)
+
+% AUTORIGHTS
+% ---------------------------------------------------------
+% Copyright (c) 2014, Ross Girshick
+% 
+% This file is part of the R-CNN code and is available 
+% under the terms of the Simplified BSD License provided in 
+% LICENSE. Please retain this notice and LICENSE if you use 
+% this file (or any portion of it) in your project.
+% ---------------------------------------------------------
 
 rcnn_model_file = './data/rcnn_models/voc_2012/rcnn_model_finetuned.mat';
 
@@ -6,7 +19,18 @@ if ~exist(rcnn_model_file, 'file')
   error('You need to download the R-CNN precomputed models. See README.md for details.');
 end
 
-use_gpu = true;
+if ~exist('use_gpu', 'var') || isempty(use_gpu)
+  use_gpu = true;
+end
+
+modes = {'CPU', 'GPU'};
+fprintf('~~~~~~~~~~~~~~~~~~~\n');
+fprintf('Running in %s mode\n', modes{use_gpu+1});
+fprintf('(To run in %s mode, call rcnn_demo(%d) instead)\n',  ...
+    modes{~use_gpu+1}, ~use_gpu);
+fprintf('Press any key to continue\n');
+pause;
+
 fprintf('Initializing R-CNN model (this might take a little while)\n');
 rcnn_model = rcnn_load_model(rcnn_model_file, use_gpu);
 fprintf('done\n');
@@ -19,7 +43,7 @@ dets = rcnn_detect(im, rcnn_model);
 showboxes(im, dets{2}(1,:));
 title(sprintf('bicycle conf = %.3f', dets{2}(1,end)));
 
-fprintf('\n> Press any key to see the top scoring person detection.');
+fprintf('Press any key to see the top scoring person detection\n');
 pause;
 
 % show top scoring person detection