Translation outputs differ with different batch sizes

Hi,

I've recently noticed that I get slightly different translation results when translating with different batch sizes. I guess this is not expected...

For example,

Batch size 100 --> PRED SCORE: -6.0490, PRED PPL: 423.68 NB SENTENCES: 5000
Batch size 150 --> PRED SCORE: -5.2232, PRED PPL: 185.54 NB SENTENCES: 5000

I'm using the latest version of OpenNMT-py

Thanks