Why do I have to use both Acceleration and LinearAcceleration?

[CoreyCoop]

I need to run a stepper continuously, reversing, and starting and stopping. So why if I am only using runForward() and runBackward(), if I don't setLinearAcceleration(), when I start from zero speed does it jump to full speed, but if I stopMove() it decelerates to a stop, and if I reverse the direction it cleanly decelerates and when it hits zero speed, it accelerates? If I use setLinearAcceleration(), but not setAcceleration(), it does not move at all. And the two functions use different parameters that are not necessarily easy to translate between!

[gin66]

any code to share ?

Constant acceleration means to speed up from standstill with constant force.
In order to speed up more gently, the linear acceleration comes into play.
Here the first n steps of the ramp are done with linear acceleration and this means linearly increasing force.
After n steps the constant acceleration sets in. When max speed is achieved, the acceleration force just vanishes.