Error using vl_nnconv

[EDINESH90]

Kindly help me, to solve the following error,

Error using vl_nnconv
An input is not a numeric array (or GPU support not compiled).

Error in vl_simplenn (line 153)
res(i+1).x = vl_nnconv(res(i).x, l.filters, l.biases, 'pad', l.pad, 'stride', l.stride) ;

Error in mdnet_features_convX (line 20)
res = vl_simplenn(net, batch, [], [], ...

Error in mdnet_run (line 37)
feat_conv = mdnet_features_convX(net_conv, img, pos_examples, opts);

Error in demo_tracking (line 22)
result = mdnet_run(conf.imgList, conf.gt(1,:), net);