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

Examples

open allclose all

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 $DefaultParallelKernels:

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:

Top

LaunchKernels

Details and Options

Examples

Basic Examples (2)