---
name: "im_concurrency_set"
section: "3"
platform: "linux"
package: "libvips-dev"
version: "7.20.7-1+b3"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/im_concurrency_set"
---

# im\_concurrency\_set(3)

set and get the number of threads to use for evaluation

## NAME

im\_concurrency\_set, im\_concurrency\_get - set and get the number of threads to use for evaluation

## SYNOPSIS

**#include \<vips/vips.h\>**

void im\_concurrency\_set( int concurrency )\
 int im\_concurrency\_get( void )

## DESCRIPTION

**[im\_concurrency\_set(3)](/im_concurrency_set/3.md)** and **[im\_concurrency\_get(3)](/im_concurrency_get/3.md)** set and get the number of parallel threads VIPS should use to calculate pixels.

A value of zero (the default) means to get the number of threads from the environment variable IM\_CONCURRENCY. If that is not set, the number of threads defaults to one.

Setting the number of threads only affects image evaluations which start after that point, it will not change the behaviour of existing evaluations.

Most command-line vips programs support the --vips-concurrency flag, which can also be used to set the concurrency.

## SEE ALSO

[im\_get\_option\_group(3)](/im_get_option_group/3.md), \`VIPS manual,' in accompanying documentation.