id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
1925	Failure to run the textbook simulation example of a pendulum - Error solving nonlinear system residualFunc2 (size 1) at time...	hurak@…	somebody	"The introductory model of a pendulum given by Peter Fritzson in his older book on pages 20 and 21 fails to simulate correctly in the recent version of OpenModelica. The code is here:

{{{
model Pendulum
  parameter Real m = 1,g = 9.81,L = 0.5;
  Real F;
  Real x(start = 0.5),y(start = 0.0);
  Real vx,vy;
equation
  m * der(vx) = -(x / L) * F;
  m * der(vy) = -(y / L) * F - m * g;
  der(x) = vx;
  der(y) = vy;
  x^2 + y^2 = L^2;
end Pendulum;
}}}

{{{
simulate(Pendulum, stopTime=4);
}}}

{{{
plot(x)
}}}

In OMEdit the simulation output contains this error message repeated a number of times:

'''stdout        | warning | Error solving nonlinear system residualFunc2 (size 1) at time 0.418728'''
------------------------------------------------------------------

When run in OMNotebook, the ""simulate"" command just returns ""false"".
------------------------------------------------------------------

Tested both on Windows (OpenModelica 1.9.0 Beta 2 nightly build r13781) and Linux (OpenModelica 1.9.0 Beta 2 nightly build  r13764, from the deb repository).

Downgrading to OpenModelica 1.8.1 solves the issue.
"	defect	closed	high	1.9.1	Backend	1.9.0Beta	worksforme