Justus3/Migration from J2: Difference between revisions
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When you build software by yourself, you have to take into account the different node architectures: the new Justus 3 nodes have AMD CPUs with the Zen5 micro architecture, whereas the old Justus 2 nodes are Intel Cascadelake. If you want to target both architectures, build for x86_64_v4. |
When you build software by yourself, you have to take into account the different node architectures: the new Justus 3 nodes have AMD CPUs with the Zen5 micro architecture, whereas the old Justus 2 nodes are Intel Cascadelake. If you want to target both architectures, build for x86_64_v4. |
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On the AMD nodes, try to compile C/C++/Fortran with the AMD compilers ( |
On the AMD nodes, try to compile C/C++/Fortran with the AMD compilers (module <code>compiler/aocc</code>), while using the Intel compilers on Intel nodes. If you experience compatibility issues, try to build with the GNU Compilers <code>compiler/gnu</code>. |
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For best performance avoid using the Intel MKL on AMD nodes. Please use the corresponding numerical libraries from AMD: |
For best performance avoid using the Intel MKL on AMD nodes. Please use the corresponding numerical libraries from AMD: |
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Revision as of 15:42, 4 November 2026
Compared to Justus2, on Justus3 there are more cores available on each node. Hence, nodes are not exclusively allocated to one single user anymore, but shared between multiple users.
Different from Justus2, on Justus3 nodes have no leading zeros in their names, e.g., the first login node is called login1 (instead of login01 on Justus2).
Building your own Software
When you build software by yourself, you have to take into account the different node architectures: the new Justus 3 nodes have AMD CPUs with the Zen5 micro architecture, whereas the old Justus 2 nodes are Intel Cascadelake. If you want to target both architectures, build for x86_64_v4.
On the AMD nodes, try to compile C/C++/Fortran with the AMD compilers (module compiler/aocc), while using the Intel compilers on Intel nodes. If you experience compatibility issues, try to build with the GNU Compilers compiler/gnu.
For best performance avoid using the Intel MKL on AMD nodes. Please use the corresponding numerical libraries from AMD:
- BLAS:
numlib/amdblis - LAPACK:
numlib/amdlibflame - SCALAPCK:
numlib/amdlibflame - FFTW:
numlib/amdfftw