How to implement the "tsearchn" algorithm 2 in a parfor loop?

Question

DroneDoctor 2018-4-12

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394545-how-to-implement-the-tsearchn-algorithm-2-in-a-parfor-loop

评论： James Cairns 2019-10-24

Hi!

I have been trying to implement the following for loop in the "tsearchn" function using a parfor.

t = nan(npt,1);            % Simplex containing corresponding input point
p = nan(npt,ndim+1);       % Barycentric coordinates for corresponding input point
X = [ones(size(x,1),1) x]; % Append 1s to vertex matrix
b = [ones(npt,1) xi];      % Append 1s to point matrix
parfor i = 1:ntri             % Return the largest simplex index
  % For each triangle
  q = b / X(tri(i,:),:);   % Compute barycentric coordinate of each point
  I = all(q > myeps,2);    % Find simplex where all coordinates are positive
  t(I) = i;                % Set simplex
  p(I,:) = q(I,:);         % Set barycentric coordinates
end

MATLAB gives me the following errors:

"The variable t in a parfor cannot be classified."

then in editor I get:

"Valid indices for t are restricted in PARFOR loops."

The same is true for the variable p.

Following the suggested links did not elucidate the matter for me.

Does anybody know how to convert it into a PARFOR loop?

Thanks!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Edric Ellis 2018-4-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394545-how-to-implement-the-tsearchn-algorithm-2-in-a-parfor-loop#answer_315543

The problem here is that the loop iterations are order-dependent. parfor can only operate when the iterations are independent - and the restrictions on indexing into t and p simply reflect that. Outputs from a parfor loop typically need to be sliced, as described in the documentation. Basically, this means that you must assign elements corresponding to the loop index only.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

DroneDoctor 2018-4-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394545-how-to-implement-the-tsearchn-algorithm-2-in-a-parfor-loop#answer_315661

Thanks for the answer. The Parallel Toolbox staff explained the issue in more detail in my service request. I was able to parallelize it and do some vectorizations. Thanks for your answer though. Highly appreciate it!