Getting different results on multiple run

I have been using emscripten to call c++ code for an image processing library.

I see two concerns with emscripten.

1. Results between native code called via node.js is different from emscripten js code. My code does use basic mathematical operation: matmul, atan2, square/sqrt in double.
1-2 % variation in feature can spoil my classifier so I am curious to know why it should be so distant from native.

2. If I run the same api in Loop on emscripten, I get two set of results ( Result A : for iteration no 1 & Result B: for other iterations (2:N)). This is serious problem for me. I didn't expect such behaviour.

Can anyone please identify the problem at hand?

@sbc100