In Windows, with

 START /node 1 /affinity ff cmd /C "app.exe"

I can set the affinity of app.exe (number of cores used by app.exe).

With a windows script, How I can change the affinity of a running process ?

PowerShell can do this task for you.

Get Affinity

$Process = Get-Process app
$Process | Select-Object ProcessorAffinity

Set Affinity

$Process = Get-Process app
$Process.ProcessorAffinity = 255

Example _{^{( 8 Core Processor )}}

Just add the decimal values together for which core you want to use.

• All 8 Cores = Value: 255 = BitMask: 0x11111111

Using with cmd.exe

You can use the PowerShell code from within the cmd shell by calling the PowerShell process with the code as an argument. Separate commands with a semi-colon.

> powershell.exe "Get-Process notepad++ | Select-Object ProcessorAffinity"

                                                         ProcessorAffinity
                                                         -----------------
                                                                       255


> powershell.exe "$p = Get-Process notepad++; $p.ProcessorAffinity = 13"

> powershell.exe "Get-Process notepad++ | Select-Object ProcessorAffinity"

                                                         ProcessorAffinity
                                                         -----------------
                                                                        13

Source

Here is a nicely detailed post on how to change a process's affinity:

Setting Processor Affinity @ EnergizedTech
archive.today / archive.org
^{_{(the broken images weren't important)}}