# Composite spaces, on() and tgv=-1

**URL:** <https://community.freefem.org/t/composite-spaces-on-and-tgv-1/3579>\
**Category:** General Discussion\
**Created:** [November 13, 2024, 11:19am UTC](https://community.freefem.org/t/composite-spaces-on-and-tgv-1/3579 "2024-11-13T11:19:12Z")\
**Posts on this page:** 1\
**Showing post:** 4

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**Author:** ![clthu](https://avatars.discourse-cdn.com/v4/letter/c/f04885/32.png) [@clthu](https://community.freefem.org/u/clthu)\
**Post date:** [December 18, 2024, 7:28am UTC](https://community.freefem.org/t/composite-spaces-on-and-tgv-1/3579/4 "2024-12-18T07:28:58Z")

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Hi professor,

Much thanks for this discussion that help me find the bugs when I do an ALE problem, I first use tgv=-1 and forget to enforce the boundary condition to the off-diagonal block of the Jacobian matrix, the convergency of Newton iteration is very slow.

My method is to set tgv=1e30, not exact Dirichlet boundary condition but the results are acceptable and easy to do parallel computation, not needed to update varf or Mat. Another way I find is to zero-out the corresponding rows in the off-diagonal block by hand, as in this post [https://community.freefem.org/t/preferred-way-to-construct-block-matrices-with-exact-dirichlet-bc-tgv-1/222/2](https://community.freefem.org/t/preferred-way-to-construct-block-matrices-with-exact-dirichlet-bc-tgv-1/222/2).

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