In the worksheet below I produce a sequence of frames for an animation by distributing the task into several threads.  The result has strange artifacts as we see in the sample.  The artifacts vary randomly from run to run.  Am I doing something wrong?

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I don't quite understand the behavior of PDEtools[declare].  My reading of the documentation is that PDEtools[declare](y(t)) tells Maple that y is a function of t, and therefore y(t) is displayed as y and the derivative of y is displayed as y_t.  I did not expect other variables to be similarly affected but apparently they are.  For instance, in the worksheet below, why is the derivative of p displayed as p_s?

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I an unable to get a numerical result out of this triple integral.  Maple runs forever.  I stopped it after about half an hour:

Int(exp(-a^2-b^2-c^2),
    a=b^2/(4*c)..infinity, b=-infinity..infinity, c=0..infinity);
value(%);
evalf(%);

Is there a trick to make it work?

In the calculation below, A and B both simplify to 1.  Why doesn't A*B simplify to 1?  Tested on Maple 2017 and 2018.