Invalid output on example/cg.py

[LWisteria]

CG is not converged only in GPU (outputs NaN)

$ python cg.py
Trial: 0
Running CPU...
Failed to converge. Increase max-iter or tol.
 CPU :  52.715649 sec
0.0486944550392
Running GPU...
Failed to converge. Increase max-iter or tol.
 GPU :  10.008114 sec
nan

Trial: 1
Running CPU...
 CPU :  39.463507 sec
6.96499403247e-05
Running GPU...
Failed to converge. Increase max-iter or tol.
 GPU :  9.536461 sec
486256.04841

Trial: 2
Running CPU...
 CPU :  39.770958 sec
4.97618615769e-05
Running GPU...
Failed to converge. Increase max-iter or tol.
 GPU :  9.568508 sec
nan