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Edric Ellis


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MathWorks

791 total contributions since 2011

Developer at MathWorks, working on Parallel Computing Toolbox. Professional Interests: parallel computing, distributed arrays, gpu

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Answered
How to fix my code with parfor-Loops array?
Output variables in parfor must be either sliced or reduction. There's more information in the doc. But basically, you cannot as...

etwa 7 Stunden ago | 0

| accepted

Answered
UndefinedFunction error was thrown on the workers for 'filedata'
I'm a little confused by your example code there - I think there must be more going on. In your code, the piece spmd imgda...

etwa 8 Stunden ago | 0

Answered
Problem with running code on gpu
Your code is not standalone, so I couldn't try it. But the main point is that you need to vectorise your code. This will speed t...

2 Tage ago | 0

Answered
Confusing results when measuring time of function on CPU/GPU with tic-toc/(gpu)timeit
Ok, there's a lot going on here. A few observations: Putting scalar values on the GPU is often counter-productive, since the im...

4 Tage ago | 1

Answered
How to make sure that function is entirely run on GPU?
Operations on gpuArray data automatically take place on the GPU. When you operate on mixed GPU and CPU data, generally the opera...

4 Tage ago | 1

Answered
Memory Parfor Needs more memory than normal
When you transfer data to the workers for a parfor loop, there is a transient increase in memory over and above what you'd expec...

7 Tage ago | 0

Answered
parfor doesn't continue to run other jobs when only one worker is working
parfor sends loop iterations to workers in groups known as "subranges" for efficiency. Also, recent versions of Parallel Computi...

10 Tage ago | 0

Answered
Use system function with parfor
It looks like your executable expects to read from input.txt and write to output.txt. This will not work in parallel because the...

16 Tage ago | 1

Answered
Trying to use gpuArray for graph function
Unfortunately, graph does not support using gpuArray data in this way. Is there some specific algorithm on your graph that you'r...

18 Tage ago | 0

Answered
Return values in a parfor loop
Fundamentally, you need to "bind" a value in to the function that gets invoked by afterEach. The simplest way to do this is to u...

21 Tage ago | 0

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Answered
SPMD and Asynchronous execution of an optimization routine?
labSend and labReceive are designed for matched communication, and there isn't any built-in facility to receive only the most re...

25 Tage ago | 0

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Answered
How to distinctly assign job and get the result of each worker using "parfor"?
This sounds more like a job for spmd . Read more about that here: https://www.mathworks.com/help/parallel-computing/spmd.html . ...

29 Tage ago | 0

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Answered
nested for inside parfor, writing to shared variable
parfor knows how to handle "reduction" variables like this correctly. (Behind the scenes, each worker process accumulates a part...

etwa ein Monat ago | 0

Answered
Starting a parfor loop
It might be useful to read this introduction to Parallel Computing Toolbox. In essense, you should simply be able to write a par...

etwa ein Monat ago | 0

| accepted

Answered
parfor does not uns parallel pool when a parfeval process is still running
Yes, this behaviour is expected - the different parallel language features parfor, parfeval, and spmd do not share the pool. You...

etwa ein Monat ago | 0

| accepted

Answered
Perfomance Loss of Matrix-Vector Multilplication on GPU with Array Indexing
Unfortunately, the expression A(8001:18000,:) requires a strided memory copy. Matrices in MATLAB (even on the GPU) are stored in...

etwa ein Monat ago | 1

| accepted

Answered
Why is MATLAB gpuArray sparse matrix multiplication so fast despite using double precision?
You should use gputime it to time operations on the GPU (although I'm not certain it will actually make a difference in this cas...

etwa ein Monat ago | 1

Answered
Parfor loop: how to keep the temporary variables ?
Output variables from parfor must be either sliced or reduction variables. So, you could adapt your code like so: parfor i = 1:...

etwa ein Monat ago | 0

| accepted

Answered
Efficient use of matfile within parfor
The problem is all to do with your assignment into v.yC. The parfor analysis cannot tell that this is safe and not order-depende...

etwa ein Monat ago | 0

Answered
How to use GPU arrayfun in App Designer: Function passed as first input argument contains unsupported 'MCOS' language feature 'CLASSDEF'
I think you simply need to make your function func3 be a normal (non-method) function. You should be able to place it in either ...

etwa ein Monat ago | 0

| accepted

Answered
parallel processing fine balance
You're quite right that in this case, you're always inevitably going to be held up by the slowest worker. It's almost impossible...

etwa 2 Monate ago | 0

| accepted

Answered
Pass NET-Object to parallel function (parfeval)
I do think parallel.pool.Constant is probably part of the answer here, but you need to make two changes: Make sure you perform ...

etwa 2 Monate ago | 1

Answered
Parfor: Unable to perform assignment because the size of the left side is 98-by-50 and the size of the right side is 107-by-50
Unfortunately, error reporting from parfor has some limitations, and specifically it cannot indicate the precise line within the...

etwa 2 Monate ago | 0

| accepted

Answered
Apply function row-wise on a tall array
You're on the right track with matlab.tall.transform, but you should call your function in that context. The function invoked by...

etwa 2 Monate ago | 1

| accepted

Answered
Some workers go idle in parfor creating a waste of computation time
The parfor implementation uses a number of different strategies to try to keep the workers busy. However, sometimes these might ...

2 Monate ago | 0

| accepted

Answered
Parallel optimization hanging on getCompleteIntervals
A few notes: The deadlock detection is for labSend and labReceive. Your parallel code is using parfor. There is no way that par...

2 Monate ago | 1

Answered
mpiprofile viewer crashes unexpectedly
I suspect the debug breakpoint is interfering with the data transfer from the spmd block back to the client. I suppose the only...

2 Monate ago | 0

| accepted

Answered
Issue with writematrix and parfor
You cannot write to the same file simultaneously from mulitple processes. (This is not a limitation specific to parfor - rather,...

2 Monate ago | 0

Answered
interrupt a function when it takes too long
The simplest approach would be to modify the potentially long-running function so that it checks whether it has exceeded its tim...

2 Monate ago | 0

Answered
Can ParallelServer be run from a client behind a NAT (connecting to cluster outside of NAT)
It should work to specify the routable address at the client using pctconfig. Something like pctconfig('hostname', '<routable a...

2 Monate ago | 0

| accepted

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