Fixed data races.

[SamyakGangwal]

Hello @zjin-lcf,

@cogumbreiro and I have been working on this repository trying to find the data races using the tool faial-drf. This commit fixes the data races in the following programs:

• aidw-cuda
• mixbench-cuda
• word2vec-cuda

If you'd like me to create a new PR for each of these programs please let me know.

Thanks!

[zjin-lcf]

Hello @SamyakGangwal Data races exist in aidw-cuda. However, could you please explain the data races in mixbench and word2vec ? Thanks!