Simulinks problems to acos

I'm computing an acos in a matlab function in my simulink problems and I got the error

Domain error. To compute complex results from real x, use 'acos(complex(x))'.

To avoid this I defined the argument of the acos as arg = max(min(arg,1),-1);

however when I do this my model becomes extremely slow to run. A simulation of 10000s that would take <1s to run now would take an hour. Any suggestions?

[John D'Errico]

Rather than using the max/min thing to catch arguments that are outside the range [-1,1], I would invest some time in learning why your equations seem to exceed those limits. Don't try to patch the problem, when that event makes little sense to ever arise. Fix the problem, don't apply a bandaid.