[petsc-users] a question about PetscSectionCreate

[leejearl]

Hi, all:
I have create a IS for every cell in dmplex by the following steps:
1. Creating a integer array which size is matched to the number of cells.
2. Use the routine "ISCreateGeneral" to create a corresponding IS.

Is there any routine which can create a IS for every cell in the dmplex 
directly?, and what is the difference between ISCopy() and ISDuplicate()?

Thanks,
leejearl

On 2017年05月28日 19:35, Matthew Knepley wrote:
> On Sun, May 28, 2017 at 6:02 AM, Lawrence Mitchell 
> <lawrence.mitchell at imperial.ac.uk 
> <mailto:lawrence.mitchell at imperial.ac.uk>> wrote:
>
>
>
>     > On 28 May 2017, at 09:16, leejearl <leejearl at 126.com
>     <mailto:leejearl at 126.com>> wrote:
>     >
>     > Hi, Dave: I want to store a PetscInt tag for every cell of the
>     dmplex with the struct. Thanks,
>
>     You probably want to use a DMLabel to store these ids. Unless you
>     have a different I'd for every cell.
>
>
> Several things to think about:
>
> 1) If you want to store a tag for EVERY cell, then just use an IS. 
> Cell numberings are guaranteed to be
>     contiguous and start from 0.
>
> 2) If you want to tag only SOME cells, then use a DMLabel as Lawrence 
> suggests. This uses hash tables
>     for fast construction, and sorted lists for fast search and retrieval.
>
> 3) If you want to store a VARIABLE number of data items per cell, then 
> use a Section and an array that you allocate.
>
>    Matt
>
>
>     Lawrence
>
>
>
>
> -- 
> 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
>
> http://www.caam.rice.edu/~mk51/ <http://www.caam.rice.edu/%7Emk51/>

-- 
李季
西北工业大学航空学院流体力学系
Phone: 17792092487
QQ: 188524324

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