# GPU is not faster CPU

**URL:** <https://itensor.discourse.group/t/gpu-is-not-faster-cpu/2100>\
**Category:** ITensor Julia Questions\
**Tags:** dmrg\
**Created:** [November 2, 2024, 10:16am UTC](https://itensor.discourse.group/t/gpu-is-not-faster-cpu/2100 "2024-11-02T10:16:09Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Jren](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@Jren](https://itensor.discourse.group/u/Jren)\
**Post date:** [November 2, 2024, 10:16am UTC](https://itensor.discourse.group/t/gpu-is-not-faster-cpu/2100/1 "2024-11-02T10:16:09Z")

</div>

Recently, I test the DMRG and TEBD by using ITensors and ITensorGPU packages. My cpu is Intel(R) Xeon(R) Gold 6130 CPU @ 2.10GHz and gpu is RTX 4070. It is found that the cpu is 5 times faster than the gpu with conserved quantum number, Did I do something wrong？

---

<div class="post-metadata">

**Author:** ![mtfishman](https://yyz2.discourse-cdn.com/free1/user_avatar/itensor.discourse.group/mtfishman/32/11_2.png) [@mtfishman](https://itensor.discourse.group/u/mtfishman)\
**Post date:** [November 2, 2024, 2:19pm UTC](https://itensor.discourse.group/t/gpu-is-not-faster-cpu/2100/2 "2024-11-02T14:19:45Z")

</div>

Using conserved quantities on GPU is still considered experimental, we recently got it to run but haven’t done any optimizing. The strategy we are using is quite naive but we are actively researching ways to make it faster! ( **EDIT:** Note that you should see better speedups on GPU as you use larger bond dimensions and fewer/less sparse symmetries, with the caveat that GPUs generally have less memory available so you may run out of memory in those limits.)

Also, we recommend not using `ITensorGPU.jl` since it is deprecated, instead you should just use the package extensions. See [Running on GPUs · ITensors.jl](https://itensor.github.io/ITensors.jl/dev/RunningOnGPUs.html).

---

<div class="post-metadata">

**Author:** ![Jren](https://avatars.discourse-cdn.com/v4/letter/j/ecccb3/32.png) [@Jren](https://itensor.discourse.group/u/Jren)\
**Post date:** [November 2, 2024, 11:55pm UTC](https://itensor.discourse.group/t/gpu-is-not-faster-cpu/2100/3 "2024-11-02T23:55:01Z")

</div>

Thank you for your reply. ：）

---

<div class="post-metadata">

**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/itensor/original/1X/d3072b13e047cd06df7f3981547c0917d940dfa4.png) [@system](https://itensor.discourse.group/u/system)\
**Post date:** [November 12, 2024, 11:55pm UTC](https://itensor.discourse.group/t/gpu-is-not-faster-cpu/2100/4 "2024-11-12T23:55:12Z")

</div>

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.