# Question about Setting BLAS Threads on Cluster

**URL:** <https://discourse.julialang.org/t/question-about-setting-blas-threads-on-cluster/108852>\
**Category:** General Usage\
**Tags:** blas, hpc, multithreading, vscode\
**Created:** [January 16, 2024, 4:42am UTC](https://discourse.julialang.org/t/question-about-setting-blas-threads-on-cluster/108852 "2024-01-16T04:42:37Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![TI36XPro](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ti36xpro/32/33658_2.png) [@TI36XPro](https://discourse.julialang.org/u/TI36XPro)\
**Post date:** [January 16, 2024, 4:42am UTC](https://discourse.julialang.org/t/question-about-setting-blas-threads-on-cluster/108852/1 "2024-01-16T04:42:37Z")

</div>

Hello,

I have a question about how BLAS threads are specified. For context, I am on my University’s HPC in an interactive session on our shared memory cluster. The partition that I am using has nodes which consist of two CPUs each with 12 cores (so 24 cores per node). I am using an interactive session because I want to do some profiling of my code using the VsCode Julia extension (using `@profview` and `@profview_allocs`). I could do this on my home PC but I have more cores to play with on the cluster.

I understand that Julia threads and BLAS threads are separate. I have code that performs many repeated operations with dense matrices and I’d like to see the impact of increasing the thread count for BLAS. I am using `MKL.jl` on intel CPUs.

To do this I request an interactive session with 24 cores (so one entire node on our shared memory cluster).

I set the following in my VsCode `settings.json`.

```json
{
    "terminal.integrated.env.linux": {
        "MKL_NUM_THREADS": "24"
    }
}

```

I also do `export MKL_NUM_THREADS=24` in the VsCode integrated terminal.

Then I go to my Julia file and do a `Shift + Enter` on the first line to start up Julia in the VsCode integrated terminal.

When I check though, I can only get 12 threads. Even if I manually set the count higher.

```julia
Threads.nthreads() # 1
BLAS.get_num_threads() # 12
BLAS.set_num_threads(24)
BLAS.get_num_threads() # Still 12

```

Does anyone know why? Or if I am doing a step wrong?