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Kernels
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Kernels

Kernels has been deprecated in favor of ParallelKernels.

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Kernels[]

gives the list of running kernels available for parallel computing.

Details

  • On a multicore computer, kernels are normally launched automatically when needed for a parallel computation.
  • All available kernels are by default used for all parallel computations.

Examples

open allclose all

Basic Examples  (1)Summary of the most common use cases

The list of currently running parallel kernels:

In[1]:=1
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https://wolfram.com/xid/0c14tj4-c0eoty
Out[1]=1

Scope  (1)Survey of the scope of standard use cases

Launch the default set of kernels:

In[1]:=1
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https://wolfram.com/xid/0c14tj4-or7uha
Out[1]=1

Give the list of currently running parallel kernels:

In[2]:=2
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https://wolfram.com/xid/0c14tj4-jtvifu
Out[2]=2

Close all running parallel kernels:

In[3]:=3
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https://wolfram.com/xid/0c14tj4-c7abox
Out[3]=3

No kernels are running:

In[4]:=4
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https://wolfram.com/xid/0c14tj4-2tsh5
Out[4]=4

Generalizations & Extensions  (1)Generalized and extended use cases

Remember the list of running kernels:

In[1]:=1
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https://wolfram.com/xid/0c14tj4-gakcs
Out[1]=1

Close all kernels:

In[2]:=2
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https://wolfram.com/xid/0c14tj4-bbt7ig
Out[2]=2

Launch copies of the previously running kernels:

In[3]:=3
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https://wolfram.com/xid/0c14tj4-h6g4x2
Out[3]=3

Properties & Relations  (2)Properties of the function, and connections to other functions

ParallelEvaluate by default does one evaluation on each kernel:

In[1]:=1
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https://wolfram.com/xid/0c14tj4-c3ihye
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0c14tj4-blyq9e
Out[2]=2

$KernelCount gives the number of running kernels:

In[1]:=1
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https://wolfram.com/xid/0c14tj4-x6lxb
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0c14tj4-npb76b
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/0c14tj4-bgtdra
Out[3]=3

Possible Issues  (1)Common pitfalls and unexpected behavior

If no kernels are available, most parallel calculations are done sequentially:

In[1]:=1
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https://wolfram.com/xid/0c14tj4-7b004
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0c14tj4-f9yca5
Out[2]=2
Wolfram Research (2008), Kernels, Wolfram Language function, https://reference.wolfram.com/language/ref/Kernels.html.
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Wolfram Research (2008), Kernels, Wolfram Language function, https://reference.wolfram.com/language/ref/Kernels.html.

Text

Wolfram Research (2008), Kernels, Wolfram Language function, https://reference.wolfram.com/language/ref/Kernels.html.

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Wolfram Research (2008), Kernels, Wolfram Language function, https://reference.wolfram.com/language/ref/Kernels.html.

CMS

Wolfram Language. 2008. "Kernels." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Kernels.html.

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Wolfram Language. 2008. "Kernels." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Kernels.html.

APA

Wolfram Language. (2008). Kernels. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Kernels.html

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Wolfram Language. (2008). Kernels. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Kernels.html

BibTeX

@misc{reference.wolfram_2025_kernels, author="Wolfram Research", title="{Kernels}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/Kernels.html}", note=[Accessed: 29-March-2025 ]}

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@misc{reference.wolfram_2025_kernels, author="Wolfram Research", title="{Kernels}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/Kernels.html}", note=[Accessed: 29-March-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_kernels, organization={Wolfram Research}, title={Kernels}, year={2008}, url={https://reference.wolfram.com/language/ref/Kernels.html}, note=[Accessed: 29-March-2025 ]}

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@online{reference.wolfram_2025_kernels, organization={Wolfram Research}, title={Kernels}, year={2008}, url={https://reference.wolfram.com/language/ref/Kernels.html}, note=[Accessed: 29-March-2025 ]}