Update core.h

The data I used to deal with is 
sweep num:512
bin num:1280
it was convenient.
but now , I deal with the data which is ..
sweep:300
bin num:534
I found that My code was wrong.
NG:int arraylength=_sweepnum<<1;//that was mistake
ok:int arraylength=_binnum<<1;
 and I fix it.