# How can I run delete in single-core mode? (On the jupyter page)

**URL:** <https://openmc.discourse.group/t/how-can-i-run-delete-in-single-core-mode-on-the-jupyter-page/5316>\
**Category:** User Support\
**Created:** [March 12, 2025, 3:58am UTC](https://openmc.discourse.group/t/how-can-i-run-delete-in-single-core-mode-on-the-jupyter-page/5316 "2025-03-12T03:58:23Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![jiangjiang](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/jiangjiang/32/3483_2.png) [@jiangjiang](https://openmc.discourse.group/u/jiangjiang)\
**Post date:** [March 12, 2025, 3:58am UTC](https://openmc.discourse.group/t/how-can-i-run-delete-in-single-core-mode-on-the-jupyter-page/5316/1 "2025-03-12T03:58:23Z")

</div>

Dear OpenMC users and experts,  
I wanna to run the openmc.deplete in single-core mode, but I didn’t find a way in the user’guide.  
such as openmc.run(threads=1), are there someway like this in the integrator.integrate() in the jupyter page?  
if not, how should I do in other way?  
Thank you so much, best wishes~(and forgive my poor English)

---

<div class="post-metadata">

**Author:** ![wahidluthfi](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/wahidluthfi/32/3375_2.png) [@wahidluthfi](https://openmc.discourse.group/u/wahidluthfi)\
**Post date:** [March 12, 2025, 4:21am UTC](https://openmc.discourse.group/t/how-can-i-run-delete-in-single-core-mode-on-the-jupyter-page/5316/2 "2025-03-12T04:21:06Z")

</div>

Hi Jiang jiang,  
if you want to limit the number of thread being used by openmc, you can set the `OMP_NUM_THREADS` environment variable same way as when you set the default nuclear data lib `OPENMC_CROSS_SECTIONS`.  
here some documentation mentioning this env variable

> **[14. Running in Parallel — OpenMC Documentation](https://docs.openmc.org/en/latest/usersguide/parallel.html?highlight=omp_num_threads)**

---

<div class="post-metadata">

**Author:** ![cjwiguna](https://yyz2.discourse-cdn.com/free1/user_avatar/openmc.discourse.group/cjwiguna/32/3728_2.png) [@cjwiguna](https://openmc.discourse.group/u/cjwiguna)\
**Post date:** [March 13, 2025, 3:43pm UTC](https://openmc.discourse.group/t/how-can-i-run-delete-in-single-core-mode-on-the-jupyter-page/5316/3 "2025-03-13T15:43:32Z")

</div>

Or you can also add this in your simulation.py:

```auto
import os

os.environ['OMP_NUM_THREADS'] = '1'

```