[trainers] fixed the moving of the model to CPU when generating images

bob/learn/pytorch/trainers/ConditionalGANTrainer.py

@@ -194,9 +194,11 @@ class ConditionalGANTrainer(object):
       # tried to move tensors, variables on the GPU -> does not work
       # let the tensors on the CPU -> does not work
       # => model has to be brought back to the CPU :/
-      self.netG = self.netG.cpu()
+      if self.use_gpu:
+        self.netG = self.netG.cpu()
       fake_examples = self.netG(self.fixed_noise, self.fixed_one_hot)
-      self.netG = self.netG.cuda()
+      if self.use_gpu:
+        self.netG = self.netG.cuda()
       vutils.save_image(fake_examples.data, '%s/fake_samples_epoch_%03d.png' % (output_dir, epoch), normalize=True)
 
       # do checkpointing