You could do it like that, but it seems pretty wasteful, especially in parallel
where you might be sending a considerable amount of data. Why not do
something like this:
1) Average all slabs into a local vector, indexed by the given k value,
meaning you have a map {k_0, k_1, ..., k_m} --> {0,1, ...,m}.
2) Now construct a scatter that maps each local vector into a parallel
vector of all the ks. The IndexSet for the from (local) vector will be
{0, 1, ..., m} and the IndexSet for the to (global) vector will be
{k_0, k_1, ... , k_m} on each process.
3) When you scatter use ADD_VALUES. Then you will have the sum, and
just scale the vector by the slab size.
Does this makes sense to you?
Thanks,
Matt
On Dec 13, 2007 5:32 PM, Randall Mackie <randy@xxxxxxxxxxxx> wrote:
I have a situation where I've put a model vector m(i,j,k) into a parallel
PETSc vector for use in my modeling code. However, I'm now adding a bit of code
where I want to do some calculations based on the 1D average of the model.
In other words, for each k, I want to average m(i,j), and so produce a new
model vector m_avg(k).
So, to do this, it would seem that I need to create a VecScatter that will,
for each layer, scatter all the m(i,j) into a 2D vector, then I can take
the average. It would seem that I need to create an Index Set to do this,
but I'm a bit confused as to how to go about it actually, since I've never
used Index Sets.
Can someone outline the basic steps given my description above?
Thanks, Randy
--
Randall Mackie
GSY-USA, Inc.
PMB# 643
2261 Market St.,
San Francisco, CA 94114-1600
Tel (415) 469-8649
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