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Bug introduced in 10.3 or earlier and persisting through 10.3.1 or later

Given:

E1 = x''[t] + x[t];
E2 = y'[t] + y[t];
E3 = (1 - DownYP[t]) Fpx[t] + DownYP[t] (Fpx[t] - .1 Sign[x'[t]]);
E4 = (1 - DownYF[t]) Ffy[t] + DownYF[t] (Ffy[t] - 20);

Events are detected:

ssol1 = NDSolve[{E1 == 0, E3 == 0,
x[0] == .1, x'[0] == 1,
DownYP[0] == 1,
WhenEvent[x[t] == .4, Print[t]]},{x, Fpx}, {t, 0, 2}, DiscreteVariables -> {DownYP[t]}];

ssol2 = NDSolve[{E2 == 0, E4 == 0,
y[0] == .1,
DownYF[0] == 0,
WhenEvent[y[t] == .04, Print[t]]},{y, Ffy}, {t, 0, 2}, DiscreteVariables -> {DownYF[t]}];

Events are not detected:

ssol3 = NDSolve[{E1 == 0, E2 == 0, E3 == 0, E4 == 0,
x[0] == .1, x'[0] == 1,
y[0] == .1,
DownYP[0] == 1,
DownYF[0] == 0,
WhenEvent[y[t] == .04, Print[t]],
WhenEvent[x[t] == .4, Print[t]]},{x, y, Fpx, Ffy}, {t, 0, 2.2}, DiscreteVariables -> {DownYP[t], DownYF[t]}];

Used to work in previous versions, but fails in 10.3 and 10.3.1. Any ideas, fixes? Thanks!

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1 Answer 1

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1
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It seems that this is a bug in Mathematica 10.3.xx. I hope it will be fixed in future versions.

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  • 1
    $\begingroup$ Did you report it to WR? Did you get any confirmation? $\endgroup$
    – Karsten7
    Jan 8, 2016 at 20:57
  • 1
    $\begingroup$ Yes I did. I was advised to downgrade and run version 10.2. $\endgroup$
    – user11311
    Jan 9, 2016 at 8:05

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