"comSubExp" introduces bad alias variables in certain cases

[Lennart Ochel]

The following model can be used to illustrate the issue:

model test
  Real x[2];
  Real a[2];
  Real z;
  parameter Real t0 = 0.5;
  Boolean b[2];
  Integer j;
  Real t[2];
equation
  x[1] = t[2];
  x[2] = t[1];
  a[1] = if time<t0 then 1.0 else sin(time);
  a[2] = if time<t0 then 1.0 else time^2;
  x[1] = a[1]+a[2];
  x[2]-a[2] = a[1];
  der(z) = x[1]/x[2];
  j = 1+integer(time);
algorithm
  if t[j] < time then
    b[j] := true;
  end if;
end test;

The module "comSubExp" introduces t[1] as alias variable, which makes the generated c code invalid, since it occurs in an if condition where it cannot be substituted.

[Lennart Ochel]

Maybe we could just do the substitution to benefit from the symbolic optimization but keep the variables and alias equations in the equation system. That shouldn't affect the performance much.

[Lennart Ochel]

Thanks, this is now working.

[Lennart Ochel]

Should this get integrated into the removeSimpleEquation module? This could reduce the back end time slightly.

[Volker Waurich]

Replying to lochel:

Should this get integrated into the removeSimpleEquation module? This could reduce the back end time slightly.

It should be since the purpose is similar. I will think about this, but the algorithm is different to removeSimpleEquations.

[Volker Waurich]

The model is now in the testsuite.

[Martin Sjölund]

Milestone renamed

[Martin Sjölund]

Milestone renamed