Project matrix from one function space to another function space

Linear Algebra
2

I’m not quite sure what you mean, but it sounds like maybe you’re looking for something like the PETScDMCollection functionality. Take a look at the following example:

from dolfin import *

# Two different meshes and function spaces:
mesh1 = UnitIntervalMesh(7)
mesh2 = UnitIntervalMesh(100)
V1 = FunctionSpace(mesh1,"Lagrange",1)
V2 = FunctionSpace(mesh2,"Lagrange",1)

# Create some function in V1:
f1 = Function(V1)
f1.interpolate(Expression("x[0]*x[0]",degree=2))

# Create a transfer matrix from V1 to V2, and use it to interpolate f1 in V2:
A = PETScDMCollection.create_transfer_matrix(V1,V2)
f2 = Function(V2)
f2.vector()[:] = A*f1.vector()

# Plot results:
import matplotlib.pyplot as plt
plot(f2)
plt.show()
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