Linux and MacOS have different results

[hailuo966]

I used pngquant on Linux and MacOS，I compressed the same pngs，but the result are different.
Linux will compressed more png than MacOS，do you konw this issue？

[kornelski]

Differences between platforms are expected for multiple reasons. Optimization is not deterministic.

• macOS version uses Apple's image decoder with Apple's color profile processing. Other versions use LCMS2. These result in slightly different interpretations of color profiles due to different implementations.

• the library uses floating-point numbers. These may give slightly different results depending on compiler optimizations and math libraries in the OS.

• the library uses multi-threading. This is a source of randomness in the program. Different machines may use a different number of threads, and threads will run at different speeds, which randomizes order of operations.

• the library may use zlib provided by the operating system, and different versions of zlib may compress better or worse. For example on Debian Linux, you probably get a very old version of zlib.