# Tagged Questions

Questions on parallel computing in Mathematica.

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### Shared variable can not be distributed again after UnsetShared

I see a weired behavior in my MM 10.3 version. Can someone reproduce it or explain what is going on? The code is easy: ...
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### How does Mathematica detect the number of cores in a system?

I'm running Mathematica 10.3.1.0 on a machine with 16 cores, but Mathematica (in the Parallel settings) says "Number of processor cores is 8." It's a 16-core Opteron 6300 chip on an Ubuntu system. All ...
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### What would you ask Mathematica to do on a big system?

Our hardware supplier has given us the opportunity to test Mathematica on a big Windows system. The specs will be 1 to 4 TB of working memory and 12 sockets with 18 cores each. I got 1 full week of ...
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### Strange behavior of ParallelTable

I was trying to carry out the following calculations: ...
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### Array elements of a vector are not filled in ParallelTable environment [duplicate]

If I use the following code the Array arr still contains zeros. ...
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### Why is a LibraryLink function, which returns a list, not parallelizing with ParallelTable?

First example: librarylink function return a list of two element ...
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### Mysterious behaviour of ParallelTable

This question is related to Export bug in combination with ParallelTable?. The following code shows an even stranger bug than in the upper question. The y-axis should always be logarithmic, but in ...
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### Export bug in combination with ParallelTable?

I am programming with Mathematica 10.3.1.0 on Windows 10 Professional 64 Bit and have an i7-4940-MX 3,1 GHz processor (4 cores). When I use in the example code below ...
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### How to speed up filling a matrix as much as possible in a loop?

In order to find the solution of an $n\times n$ system of nonlinear equations by the method $x_{k+1}=x_k-D_k^{-1}f(x_k)$ where $D_k$ is an approximation of the Jacobian and defined by ...
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### ParallelTable slow down, Region functions

I am experiencing speed issues with ParallelTable. There are a few related problems on SX posted here and here, but no resolution. The various respondents to those ...
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I'd like to know how CreateScheduledTask and StartScheduledTask work internally. When I run the following code: ...
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### ParallelTable pending the MathKernel after execution

I have done a ParallelTable computation in script mode. After execution, the output is fine and I've got all the data I needed. but the kernel seems pending, ...
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### Is it possible to Parallelize Select?

Given a large list of elements, is it possible to improve Select by parallelizing? An example: from a 10,000,000-element list of integers between 1 and 10, select ...
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### Invoking functions in other kernels

Suppose one wants to parallelize as much as possible N tasks, each task produces a graphics via ParametricPlot or something like that. If the system is allowed to ...
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### Parallelize Factor or Simplfy

I want to calculate the following example: Factor[ a+b+c+d+......(very complicate)] Factor[ a+e+f+d+......] Factor[ h+b+c+g+......] Usually, these calculations ...
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### How to parallelize this code?

Initialize a matrix a with value of $\alpha$ in central cell as "ice", and $\beta$ in every other cell. ...
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### Optimizing a series of basic matrix operations—scaling doesn't seem right with matrix size

I have a simple operation that I'd like to apply to an n×n matrix. My problem (well, one of them...) is that it runs in, say, 4 seconds for a 100×100 matrix, but it took five and a half minutes to run ...
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### Parallelize in Mathematica [duplicate]

Here is two test to understand the parallelize in Mathematica: ...
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### Can equation solving be done in parallel?

I'm solving a set of equations that look like: ...
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### LaunchKernels behavior

I have one processor with 2 cores on my local computer. CloseKernels[];LaunchKernels[] (* {"KernelObject"[1, "local"], "KernelObject"[2, "local"]} *) I can't ...
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### Using counters within parallelize

I am running a lengthy do loop and I wish to use Parallelize so that multiple kernels are used. What I do in the loop is update a set of counters that report the ...
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### Parallel execution of an instructions block

I regularly use Parallelize and ParallelMap, andI've been reading the manual pages for parallel computing instructions but i could not find what I am looking for. Assume I have a sequence of ...
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### Efficient and fastest way to execute 4 nested loops

I have a question regarding the use of ParallelDo. I tried to parallelize the following code involving four nested Do loops by ...
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### how to parallelize nested do loops [closed]

I have four Do loops which the outer loops iterate over the inner loops. This is my code ...
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### Parallel function evaluation for minimal value

I am asking myself, if the evaluation of a function f looking for a minimal value over a discrete set of values can be parallelize (brute scan for a potential ...
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### Causes “libGL error: failed to load driver: swrast” an Huge Overhead in Parallel under Version 10.3?

Under Linux (SUSE Linux Enterprise 11) for Mathematica Version 10.2/10.3 I observe the following error in parallel ...
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### Is there any way to use parallel computation for all code as automatically? [duplicate]

I need help to learn that Is there any way to use parallel computation for all code as automatically?
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### Improving the speed of an optimization algorithm via compilation and parallellization

I have written an implementation of eight variants of the PSO-algorithm and I want to test them over a set of test functions. I am using parallelization as it improves the speed a lot and I have also, ...
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### Why does ParallelDo return wrong number of results

I am testing out some optimization algorithms. I have written the code with a Do loop inside a Do loop. The inner loop is the algorithm itself and the order the steps are executed is very important. ...
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I am using Eigenvalues a large number of times on a machine with 8 cores. When I run Eigenvalues one time without any parallel ...
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### How to speed up summing a large number of vectors

First let me explain what I am trying to do in my code. Assume that I send a very short chirp (2,000 ms long) into a domain filled with 20,000 particles randomly scattered in the domain. The ...
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### Parallelization [closed]

I am new to mathematica and have the following question regarding parallelization of the code. I have an input data which is of the form ...
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### ParallelDo errors using Physical Constant and a list

I am new to using Mathematica in parallel and need help with the following code. When it is not run in parallel as follow, it works. ...
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### Distribute Definitions to different Evaluator

I would like to pass on a definition from one Kernel to the other. With that I mean manually configured Kernels. In this case, I do not want to use the inbuilt Parallelization options, in order to ...
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### Is there a way to specify which kernel is used to import files (SOLVED)?

Following up on a previous question in which I encountered a memory leak in the JSON importer I have created a SandBox script that will run the Import and analysis on a separate kernel, which be ...
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### Selecting the parallel kernels where tasks can be executed

When I use ParallelSubmit, is it possible to select on which kernel a task can possibly be executed? For example if have 3 parallel kernels, can I only use 2 of ...
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### InstallJava on a parallel kernel while debugging in Wolfram Workbench

Here's my problem. I need to create a link between a client that is a parallel Wolfram kernel and a server through a Java API. I'm using Wolfram Workbench in debugging mode (like most of the time ...
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### The module load only works for the first node, not all. Is there's a way to specify the full path to the math command when launching remote kernels

Running a Mathematica .m file in cluster for parallel computing. But get an error "bash: math: command not found". Is there's a way to specify the full path to the ...
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### Parallel evaluation of symbolic matrix eigenvalues

I'm trying to find eigenvalues of symbolic hermitian 40x40 block matrix. It is made from 20 2x2 matrices like this: ArrayFlatten[Table[M[m,n],{m,1,20},{n,1,20}]] ...
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### How to parallelize a Do loop containing URLFetchAsynchronous?

I'm have a simple piece of code: results={}; Do[If[!FailedQ[g = grab[i]], AppendTo[results, g]], {i, 2000000, 3000000}] I had thought that the simplest way to ...
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I have been regularly using parallel kernels on my machine but this morning all I receive is a cryptic error whenever I call any parallel function (LinkOpen::linke). As far as I can see sequential ...
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### memory leaks using NIntegrate on parallel kernel

Bug fixed in version 10.2.0 I'm running a large computation in parallel and the memory usage of the parallel kernels is increasing with every iteration of the calculation. Neither ...