I tried to run the example in 2.6 Stokes equations

The results that I got in line 8 was different from what it was in the documentation.

## [code]V.ndof = 1664 , Q.ndof = 2334

NgException Traceback (most recent call last)

in

4 X = FESpace([V,V,Q])

5

----> 6 gfu = SolveStokes(X)

in SolveStokes(X)

12 res = gfu.vec.CreateVector()

13 res.data = -a.mat * gfu.vec

—> 14 inv = a.mat.Inverse(freedofs=X.FreeDofs(), inverse=“umfpack”)

15 gfu.vec.data += inv * res

16

NgException: UmfpackInverse: Numeric factorization failed.[/code]

It should be V.ndof = 1660 , Q.ndof = 2328.

Could you tell me why i got this error and how to fix this problem? Thank you so much.