Wrong symbolic simplification

[Vitalij Ruge]

The follow is a model with wrong symbolic simplification.

model A
  Real x1;
  Real x2;
  Real y;
  Real w;
equation
  x1 = 0/y;
  y*x2 = 0;
  der(y) = 1;
  w = x1/sin(x1);
initial equation
  y = 0;
  x2 = 1;
end A;

Output with +d=optdaedump

Known Variables (constants) (3)
=============================
1:  x1:VARIABLE(start = 0.0 )  = 0.0 .A, .Real type: Real (start = 0.0 )
2:  w:VARIABLE(start = 0.0 )  = 0.0 .A, .Real type: Real (start = 0.0 )
3:  x2:VARIABLE(start = 0.0 )  = 0.0 .A, .Real type: Real (start = 0.0 )

Initial Equations (2, 2)
)
=========
1 : y = 0.0
2 : 0.0 = 1.0

Error 1
If x1 is 0 then w is "division by zero" or 1.

Error 2
x1 is (to runtime = 0) not define (x1 =0/0).

Error 3
From y*x2 = 0 not follows x2 = 0/y = 0. In this case is correct x2 = 1, y = 0
(see initial equation).

[Jens Frenkel]

The error is caused by Expression Simplification because this reports the frontend

class SimplifyEquations
  Real x1;
  Real x2;
  Real y;
  Real w;
initial equation
  y = 0.0;
  x2 = 1.0;
equation
  x1 = 0.0;
  y * x2 = 0.0;
  der(y) = 1.0;
  w = x1 / sin(x1);
end SimplifyEquations;

[Martin Sjölund]

Postponed until 1.9.1

[Martin Sjölund]

This ticket was not closed for 1.9.1, which has now been released. It was batch modified for milestone 1.9.2 (but maybe an empty milestone was more appropriate; feel free to change it).

[Martin Sjölund]

Milestone changed to 1.9.3 since 1.9.2 was released.

[Martin Sjölund]

Moved to new milestone 1.9.4

[Martin Sjölund]

Milestone pushed to 1.9.5

[Martin Sjölund]

Milestone renamed

[Martin Sjölund]

Ticket retargeted after milestone closed

[Martin Sjölund]

Milestone moved to 1.12.0 due to 1.11.0 already being released.

[Francesco Casella]

Replying to vitalij:

Error 1
If x1 is 0 then w is "division by zero" or 1.

As of v1.13.0-dev-155-g68350e9 a division by zero error is generated and the simulation is aborted at initialization.