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$KernelID
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$KernelID

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is a unique ID number assigned to each running parallel kernel.

Details

  • The value of $KernelID for the master kernel is 0.
  • The value of $KernelID for each subkernel is a distinct positive integer, assigned when the kernel is launched.
  • Values of $KernelID are unique but not necessarily contiguous.

Examples

open allclose all

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

Obtain the ID value of each running parallel kernel:

In[1]:=1
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https://wolfram.com/xid/05gqao1yu8-ha3fm0
Out[1]=1

Generalizations & Extensions  (1)Generalized and extended use cases

$KernelID on the master kernel gives 0:

In[1]:=1
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https://wolfram.com/xid/05gqao1yu8-c9zsha
Out[1]=1

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

The output form of a kernel object indicates its $KernelID:

In[1]:=1
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https://wolfram.com/xid/05gqao1yu8-njw1e3
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/05gqao1yu8-e722h
Out[2]=2

Newly launched kernels get new ID values:

In[1]:=1
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https://wolfram.com/xid/05gqao1yu8-bv163
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/05gqao1yu8-ecubn8
Out[2]=2

Possible Issues  (1)Common pitfalls and unexpected behavior

Kernel ID values are not necessarily contiguous:

In[1]:=1
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https://wolfram.com/xid/05gqao1yu8-de6sra
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/05gqao1yu8-bme0ld
Out[2]=2
In[3]:=3
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https://wolfram.com/xid/05gqao1yu8-b0ai6c
Out[3]=3
Wolfram Research (2008), $KernelID, Wolfram Language function, https://reference.wolfram.com/language/ref/$KernelID.html.
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Wolfram Research (2008), $KernelID, Wolfram Language function, https://reference.wolfram.com/language/ref/$KernelID.html.

Text

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

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

CMS

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

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

APA

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

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

BibTeX

@misc{reference.wolfram_2025_$kernelid, author="Wolfram Research", title="{$KernelID}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/$KernelID.html}", note=[Accessed: 25-April-2025 ]}

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@misc{reference.wolfram_2025_$kernelid, author="Wolfram Research", title="{$KernelID}", year="2008", howpublished="\url{https://reference.wolfram.com/language/ref/$KernelID.html}", note=[Accessed: 25-April-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_$kernelid, organization={Wolfram Research}, title={$KernelID}, year={2008}, url={https://reference.wolfram.com/language/ref/$KernelID.html}, note=[Accessed: 25-April-2025 ]}

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@online{reference.wolfram_2025_$kernelid, organization={Wolfram Research}, title={$KernelID}, year={2008}, url={https://reference.wolfram.com/language/ref/$KernelID.html}, note=[Accessed: 25-April-2025 ]}