Thanks very much for this. I had assumed by specifying `\[f]` that I *had* given just one boundary condition. I tried your solution but ran into a problem which I have raised as a ticket as you suggest: https://github.com/ApproxFun/ApproxFun.jl/issues/159 <https://github.com/ApproxFun/ApproxFun.jl/issues/159>
Dominic Steinitz [email protected] http://idontgetoutmuch.wordpress.com > On 13 Apr 2015, at 03:00, Sheehan Olver <[email protected]> wrote: > > You have too many boundary conditions: dirichlet conditions on a rectangle > defaults to conditions on all 4 sides. Imposing on just the left side gives > an answer: > > d = domain(Fun(identity,[0.0,1.0])) > f = Fun(x->exp(-x^2),d) > D = Derivative(d) > L = 2.0D⊗I+I⊗D > u = [ldirichlet(d)⊗I,L]\[f] > > though you may need another boundary condition. to get the answer you are > looking for. > > PS I'm more likely to see this if you post it as a git issue on ApproxFun's > github page. > > > On Sunday, April 12, 2015 at 12:10:24 AM UTC+10, idontgetoutmuch wrote: > I am trying to solve a first order PDE to which I know the solution $2u_x + > u_y = 0$ with boundary condition $u(x,0) = exp{-x^2}$. The solution is > $exp{-(x-2t)^2}$. I have tried the code below > > Pkg.checkout("ApproxFun") > > using ApproxFun > > d = domain(Fun(identity,[0.0,1.0])) > > f = Fun(x->exp(-x^2),d) > > D = Derivative(d) > > L = 2.0D⊗I+I⊗D > > u = [dirichlet(d^2),L]\[f] > > > but I get endless > > WARNING: Maximum number of iterations 100000 reached > WARNING: Maximum number of iterations 100000 reached > WARNING: Maximum number of iterations 100000 reached > > Any help would be gratefully received. >
