LaunchKernels

LaunchKernels[]

launches all currently configured parallel subkernels.

LaunchKernels[n]

launches n local subkernels on the current computer.

LaunchKernels[ker]

launches the kernel specified by ker.

LaunchKernels[{ker₁,ker₂,…}]

launches the kernels ker_i.

Details and Options

LaunchKernels[] uses $DefaultKernels to determine the list of kernels to launch.
The ProgressReporting option specifies whether to report the progress of kernel launching.
The default value is ProgressReporting:>$ProgressReporting.
Additional configurations for kernels on remote machines can be made available with the Wolfram Lightweight Grid and the Cluster Integration Package.

Examples

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Basic Examples (2)

Launch the default kernels:

Close all running kernels and start two new ones:

LaunchKernels by default displays information about its progress:

Scope (12)

Kernel Specifications (4)

Launch the default kernels as described in $DefaultKernels:

Launch two more local kernels, in addition to those already running:

Launch kernels on a remote machine:

Use KernelConfiguration to specify additional details of the desired kernels:

Local Kernels (3)

Use a specific local kernel, given by its absolute path:

Alternatively, specify the properties with KernelConfiguration:

For local kernels, the default number of parallel kernels is equal to $ProcessorCount, license permitting:

SSH Kernels (3)

Give the path to the remote kernel and number of kernels as URL parameters:

Alternatively, specify the path and kernel count as properties of KernelConfiguration:

Specify the remote operating system to automatically choose a suitable kernel command:

When using a URL short form, the number of parallel kernels can be specified with "?n":

WSTPServer Kernels (1)

Connect to a WSTPServer and request a number of parallel kernels:

LWG Kernels (1)

Launch two parallel kernels from a LightweightGrid server with default port and manager URL:

Generalizations & Extensions (1)

Close all kernels:

Launch copies of the previously running kernels:

Options (2)

ProgressReporting (2)

Do not show a temporary progress report:

Show a progress report even if the default $ProgressReporting may be False:

Applications (1)

Measure the speedup of the same calculation with different numbers of kernels used:

Properties & Relations (1)

Distributed definitions and shared variables apply to running kernels and new ones:

Packages read with ParallelNeeds also apply to running and new kernels:

Close all running kernels and launch new ones:

The new kernels inherit previously distributed definitions and shared variables:

The new kernels also inherit packages read previously:

Possible Issues (4)

If any kernels are already running, LaunchKernels[] does not launch the default kernels:

Close all running kernels, then launch the default set of kernels:

Kernels may be automatically launched when first needed:

Manually close the kernels:

Now, no kernels are launched automatically:

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

No kernels are launched by default on a single-core computer:

Specify the number of desired kernels to launch them anyway:

Neat Examples (1)

Specify a kernel on a remote machine:

Ask it for the number of processor cores:

Update the kernel specification with the kernel number returned:

Launch the parallel kernels:

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LaunchKernels

Details and Options

Examples

Basic Examples (2)