[KISEMA-1609] Commutative Operators in Dataflow should have free port constraints

[fabianheyer]

[Issue KISEMA-1609 migrated from JIRA, first reported on 2021-03-23]

In SCCharts dataflow, all simple arithmetic actors such as +, *, &, etc. which are commutative should have free port constraints to allow the layout to avoid some edge crossings. See the SCChart below and the attached image for an example where this could yield a diagram with at least two less edge crossings.

@ClocksUseSD
scchart RollingBall {
  output float accel // output acceleration change
  
  input float targetV = 10 // target velocity input
  input float currentV = 0 // current velocity input
  input float Kp, Ki, Kd // PID calibration variables input
  input float dT = 0 // delta Time input
  float prevError = 0 // error in the previous tick
  
  float error = 0// divergence from the target velocity
  float P, I, D // internal variables for PID calculation
  clock t = 0 // clock for real time calculation

  dataflow:
  prevError = error
  error = targetV - currentV
  P = Kp * error
  I += error * t
  D = (currentV - prevError)/t
  accel = P + Ki * I + Kd* D
}

Edit 2022-04-20: included attatched image

[Skgland]

@fabianheyer is it intentional that the attached image has not been migrated?

[fabianheyer]

@Skgland It's included now, thanks for the heads-up.