real_t getCPUtime() does not have enough accuracy when enabling __USE_SINGLE_PRECISION__

[hmojtaba]

real_t type is float when we enable USE_SINGLE_PRECISION.
and then all usages of cputime won't work because float doeas not have enough accuracy for this purpose.

for my own project I changed any usage related to cputime to double instead of real_t no matter if USE_SINGLE_PRECISION was enabled or not.