cpucount: functions module for shellfire

This module provides utility functions for counting cpus to a shellfire application. It is deliberately separate to the core module as it is not likely to be frequently needed.

An example user is the cmake-scripted tool.

Compatibility

• Tag release_2015.0117.1750-1 is compatible with shellfire release release_2015.0117.1750-1.

Overview

To find the number of hyperthreaded CPUs on a system:

local cpucount_discoveredNumberOfCpus
cpucount_findNumberOfHyperthreadedCpus
echo "Number of CPUs: $cpucount_discoveredNumberOfCpu"

local cpucount_makeJobs
local cpucount_makeLoadAverage
cpucount_computeMakeJobsAndLoadAverage 0 75
echo "Number of make jobs: $cpucount_makeJobs"
echo "Make load average: $cpucount_makeLoadAverage"

Importing

To import this module, add a git submodule to your repository. From the root of your git repository in the terminal, type:-

mkdir -p lib/shellfire
cd lib/shellfire
git submodule add "https://github.com/shellfire-dev/cpucount.git"
cd -
git submodule init --update

You may need to change the url https://github.com/shellfire-dev/cpucount.git" above if using a fork.

You will also need to add paths - include the module paths.d.

Namespace cpucount

To use in code

If calling from another shellfire module, add to your shell code the line

core_usesIn configure

in the global scope (ie outside of any functions). A good convention is to put it above any function that depends on functions in this module. If using it directly in a program, put this line inside the _program() function:-

_program()
{
	core_usesIn cpucount
	…
}

Functions

---

cpucount_findNumberOfHyperthreadedCpus

Parameter	Value	Optional

Takes no parameters.

Sets cpucount_discoveredNumberOfCpus to the number of hyperthreaded CPUs.

---

cpucount_computeMakeJobsAndLoadAverage

Parameter	Value	Optional
configuredCpuCount	Integer. Set to 0 to use the value of cpucount_discoveredNumberOfCpus. Set to a negative value to use cpucount_discoveredNumberOfCpus reduced by the magnitude of the negative value.	No
configuredLoadAverageCorrection	Integer percentage between 0 and 100. Used to reduce the load average by this percent.	No

Sets cpucount_makeJobs to the number of make jobs and cpucount_makeLoadAverage to the make load average to use.

The configuredLoadAverageCorrection is used to overcome the shell's lack of floating point maths. For instance, if the uncorrected load average would be 4.00, using a configuredLoadAverageCorrection of 75 will result in cpucount_makeLoadAverage being 3.25. If cpucount_makeLoadAverage would be 0.00 then it is forced to 0.01.