nbody example fails

[bwanaaa]

~/taichi/taichi/python/examples/simulation$ python nbody_3d.py

[Errno 2] No such file or directory: '../output/frames/task-2017-01-05-20-58-23-r03610/'
Simulation time: 0.0
nbody.cpp[201]: node_end = 297117
Time: 0.139370918274
Segmentation fault (core dumped)

I think the error is nbody.py where this line:
self.directory = '../output/frames/' + get_uuid() + '/'

Maybe should be:
self.directory = tc.get_root_directory() + 'output/frames/' + get_uuid() + '/'

added this:
import taichi as tc

but then get this error:

python nbody_3d.py 
[Errno 2] No such file or directory: '/home/me/taichi/output/frames/task-2017-01-05-21-19-15-r07527/'
Simulation time: 0.0
nbody.cpp[201]: node_end = 297117
Time: 0.115436077118
Segmentation fault (core dumped)

as if it cannot os.mkdir(self.directory)

[yuanming-hu]

Thanks for pointing this out. I fixed the directory issue and it runs well on my machine. Could you please have a try?

[iamyoukou]

I had the same error on Arch Linux. And I
mkdir $TAICHI_ROOT_DIR/taichi_outputs
as @IteratorAdvance you pointed out in another issue, and problem solved.

[yuanming-hu]

OK, thanks. I'll put a script at startup so that users do not have to manually mkdir.