Added December 27, 2018.
Taken from https://en.wikipedia.org/wiki/List_of_nonlinear_partial_differential_equations
Chaffee Infante equation. Solve for \(u(x,t)\) \[ u_t = u_{xx} + \lambda (u^3 - u) = 0 \]
Mathematica ✗
ClearAll["Global`*"]; pde = D[u[x, t], t] - D[u[x, t], {x, 2}] + lambda*(u[x, t]^3 - u[x, t]) == 0; sol = AbsoluteTiming[TimeConstrained[DSolve[pde, u[x, t], {x, t}], 60*10]];
Failed
Maple ✓
restart; pde := diff(u(x,t),t)-diff(u(x,t),x$2)+lambda*(u(x,t)^3-u(x,t))=0; cpu_time := timelimit(60*10,CodeTools[Usage](assign('sol',pdsolve(pde,u(x,t))),output='realtime'));
\[u \left ( x,t \right ) ={\frac {1}{2}\tanh \left ( -{\frac {3\,\lambda \,t}{4}}+{\frac {\sqrt {2}x}{4}\sqrt {\lambda }}+{\it \_C1} \right ) }-{\frac {1}{2}}\]
____________________________________________________________________________________