Re: Re: FindRoot: Failed to converge to the

*To*: mathgroup at smc.vnet.net*Subject*: [mg57494] Re: [mg57481] Re: [mg57464] FindRoot: Failed to converge to the*From*: <topolog at gazeta.pl>*Date*: Sun, 29 May 2005 21:00:11 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

> What was the code you used in version 4? Here it is: dYdX = EQJ; Y1X1 = {v[z1] == BCV1, v'[z1] == BCV2}; eqset = Join[{dYdX}, Y1X1]; FindRoot[ ( NDSolve[eqset /. {W -> w}, v, {z, z1, z2}][[1,1,2]] )[z2] == BCV3, {w, {w1, w2}}] As you can see, in version 5.1 I based on the old 4.0 code as close as possible. Starting values for W (w1, w2) are appropriately chosen in both cases. Regards > > On 5/28/05, topolog at gazeta.pl <topolog at gazeta.pl> wrote: > > Dear Mathematica Users, > > > > This is a valid part of a code that provides shooting method to > > solve equation EQJ = J1(W,z)*v(z) + J2(W,z)*v'(z) + J3(W,z)*v''(z) > > == 0 (--THIS IS THE CORRECT FORM!!--) > > with W - an eigenvalue: > > > > dYdX[W_?NumericQ] := EQJ; (* the equation *) > > Y1X1[W_?NumericQ] := {v[z1] == BCV1, v'[z2] == BCV2}; (* boundary > > conditions, BCV2 is W-dependent *) > > eqset[W_?NumericQ] := Join[{dYdX[W] == 0.}, Y1X1[W]]; (* the set of > > the above *) > > > > (* function that solves eqset for the specified W *) > > ndsolut[W_?NumberQ] := NDSolve[eqset[W], v, {z, z1, z2}][[1, 1, 2]]; > > > > (* searching for W that satisfies another boundary condition *) > > FindRoot[ndsolut[W][z2] == BCV3, {W, W1, W2}] > > > > While in version 4.0 of Mathematica similar code was able to find > > solutions quickly and accurately, the 5.1 version breaks after 100 > > iterations in FindRoot: > > > > FindRoot::cvmit: Failed to converge to the requested accuracy or > > precision within 100 iterations > > > > Any sugestion, please. > > > > Rafal Kosinski > > > > P.S. The J-functions are rather complex so I do not present them > > here. They are dependent of z-coordinate through > > InterpolatingFunction[{{0., 3000.}}, <>][z] and of W in powers from > > 1 to 10. > > > > > > > > > > > > > >