If you know the union of the different sparsity patterns, after you preallocate you can set all zeros to use all the entries. This way PETSc will not complain about new nonzeros in successive assemblies. Il 25 Set 2017 7:01 PM, "Kong, Fande" <[email protected]> ha scritto:

Hi Matt,

Thanks for your reply.

The sparsity pattern is slightly different from one Newton iteration to another. We preallocate enough memory at the beginning, and want to use that memory for the following iterations.

Does PETSc accutally free the preallocated (extra) memory? I so cannot use it during the second iteration.

Fande,

On Mon, Sep 25, 2017 at 9:43 AM, Matthew Knepley <[email protected]> wrote:

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On Mon, Sep 25, 2017 at 11:39 AM, Kong, Fande <[email protected]> wrote:

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Hi All,

A matrix is created with the right preallocation, and then MatAssembly is called. The preallocation info will be removed. We insert any values then, and will encounter an malloc error.

My question is that we was intending to design like this way? Attached simple example demonstrates what I am talking about.

Yes, this is the intent. Why are you assembling? Could you use MAT_ASSEMBLY_FLUSH?

Matt

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Fande,

-- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener

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