Why numel() is not accepted with a gpuArray

2022 9 14
1 个回答
回答已采纳
更新时间：2022 9 18
13 次查看（30 天）

0 个投票

pcGpu = gpuArray(5:100);
r = arrayfun( @numel, pcGpu );
simple line of code above, although numel is supported with gpuArray, I still get following feedback:
Function passed as first input argument contains unsupported or unknown function 'numel'.
For more information see Tips.
Am I doing sth. wrong?
Thanks, Song

5 个评论
显示 3更早的评论 隐藏 3更早的评论

Walter Roberson
Walter Roberson 2022-9-14
Why would you want to apply numel to each entry in a gpu Array? It would be asking for numel() of a scalar at each step, so the effect would be the same as ones(size(pcGpu), 'gpuArray')
Song Decn
Song Decn 2022-9-15
Thanks Walter for the quick response.
Acutally what I really want to implement is to use GPU to execute a function containing numel(), like this:
function f = testFcn(a)
f = numel(a);
end
pcGpu = gpuArray(5:100);
% r = arrayfun( @numel, pcGpu );
r = arrayfun( @testFcn, pcGpu );
But still I get the following error:
Error using Untitled2 (line 24)
Function passed as first input argument contains unsupported or unknown function 'numel'.
For more information see Tips.
Error in 'testFcn' (line: 2)
So, does it mean that I can't call numel in a function for gpuArray?
I barely find examples for gpuArray calling in callback function.
Song Decn
Song Decn 2022-9-15
编辑：Walter Roberson 2022-9-15
I tried another way:
pcGpu = gpuArray(5:100);
a = 1:10;
% r = arrayfun( @numel, pcGpu );
f = @(x)testFcn(a,x);
arrayfun( f, pcGpu );
function f = testFcn(a, pcGpu)
for i = 1:numel(a)
f = pcGpu + i;
end
end
still not working:
Error using Untitled2 (line 26)
Use of functional workspace is not supported.
For more information see Tips.
Walter Roberson
Walter Roberson 2022-9-15
Are you applying numel to the entire array, or are you applying numel to each element of an array? When you use arrayfun then by definition the function is passed one element of the array.
arrayfun over a gpuArray does not support anonymous functions with captured variables.
Walter Roberson
Walter Roberson 2022-9-15
for i = 1:numel(a)
f = pcGpu + i;
end
That overwrites all of f each iteration, so if you could get it to work, the result would be the same as if you had done
i = numel(a);
f = pcGpu + numel(a);
Reminder: you can pass numel(a) in as a parameter.

请先登录，再进行评论。

请先登录，再回答此问题。

 采纳的回答

Walter Roberson
Walter Roberson 2022-9-15
编辑：Walter Roberson 2022-9-15

0 个投票

https://www.mathworks.com/help/parallel-computing/gpuarray.arrayfun.html
numel is not supported inside any function run on a gpuArray by using arrayfun. The above link lists all supported functions.
Remember that arrayfun on a gpuArray runs all aspects on the gpu. Variables not specifically configured as gpuArray have to be converted to gpuArray internally because the entire function runs on the gpu.

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

Song Decn
Song Decn 2022-9-18
Thanks a lot Walter. I learned a lot and now have to rewrite my code now.

请先登录，再进行评论。

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 GPU Computing in MATLAB 的更多信息

产品

版本

R2020b

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by