convergence criteria

[vinamrabenara]

breeze/math/src/main/scala/breeze/optimize/FirstOrderMinimizer.scala

Line 240 in 31e9a79

if (info.length >= 2 && (state.adjustedValue - info.max).abs <= tolerance * (if (relative) state.initialAdjVal.abs

I am not able to understand this convergence criteria ^ . Could someone point me to any online resource that might explain this. Is this a standard convergence check? What does it actually check. I did not find any similar implementaion in other optimization packages.