On Mon, 29 May 2017 at 08:39, leejearl <leejearl@126.com> wrote:
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?,

I don't think so as Plex would have to somehow know what geom quantity to use to define the size of IS (e.g. vertex, cell, face, edge)

and what is the difference between ISCopy() and ISDuplicate()?

ISDuplicate allocates memory for a new with the same comm and layout as the original IS AND copies values from the original IS into the new one. (Note that this is slightly different from other duplicate functions like VecDuplicate which only allocate memory and does not copy values from the orig vec.)

ISCopy does not allocate memory for the IS (passed as the second arg), it only performs the copy of values.

Thanks 
  Dave 



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@imperial.ac.uk> wrote:


> On 28 May 2017, at 09:16, leejearl <leejearl@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



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