Question #159021 on DOLFIN changed: https://answers.launchpad.net/dolfin/+question/159021
Johan Hake posted a new comment: On Thursday May 26 2011 07:25:55 Douglas Brinkerhoff wrote: > Question #159021 on DOLFIN changed: > https://answers.launchpad.net/dolfin/+question/159021 > > Douglas Brinkerhoff posted a new comment: > How would one create an expression out of some already known data? It > seems as though the Expression class is very good for building a > spatially dependent combination of parameters and elementary functions, > but I'm not sure how I could turn some list or array of data into an > expression. Try this: from dolfin import * mesh = UnitCube(10,10,10) V = FunctionSpace(mesh,"Lagrange",1) W = MixedFunctionSpace([V,V]) u0 = Function(V) v0 = Function(V) # Fill u0, v0 u0.vector()[:] = 1.0 v0.vector()[:] = 2.0 class InitConditions(Expression): def __init__(self, u0, v0): self.u0 = u0 self.v0 = v0 def eval(self, value, x): value[0] = self.u0(x) value[1] = self.v0(x) def value_shape(self): return (2,) init_cond = InitConditions(u0, v0) U0 = project(init_cond, W) ############ This can be done as a compiled expression for better speed up. But I guess a Python Expression is enough for this case. Johan > Stated another way: > > In my particular application, I'm solving for vertically averaged > velocities within glacial ice (Basically shallow water equations, with > some extra stuff). There is a 0-order solution which is solely a > function of local geometry, e.g. Surface slope and ice thickness, which > are currently parameterized as coefficients. This is just a simple > calculation, not a PDE, and it is also stored as coefficients, called u0 > and v0. I want to use this zero order solution as an initial guess for > a non-linear system of equations which yields a first order solution. > Is there a way to package u0 and v0 as an expression, or something like > it, such that it is available to be projected, assigned, or > interpolated? -- You received this question notification because you are a member of DOLFIN Team, which is an answer contact for DOLFIN. _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
