Cray Compiler Overview

Software enhancements and support

This section describes software enhancements and support details for the HPE CCE 21.0.0 release.

Language technology

HPE Cray Fortran fully supports the Fortran 2018 standard.
The C and C++ compilers are based on Clang and LLVM 21.0.0.
- C fully supports c89 with partial support for c99, c11, and c17.
- C++ fully supports C++17 with partial support for C++20 and C++23.
LLVM version 21.0.0 base.

Miscellaneous features and enhancements

Support for LLVM 21 base (merges up to Dec 12, 2025 - LLVM version 21.1.8)
Support for Clang extensions for AMD GPU floating-point atomics: https://clang.llvm.org/docs/LanguageExtensions.html#extensions-for-controlling-atomic-code-generation
Added or extended support for the following OpenMP features:
- For OpenMP 6.0
  - groupprivate directive
  - Fortran: workdistribute construct
  - Fortran: automap modifier for declare target
  - local clause for declare target
  - variable-category modifier for default clause
- For OpenMP 5.2
  - Extended declare mapper to support iterators and present modifier
  - Support omp_initial_device and omp_invalid_device identifiers
  - Fortran: doacross clause for stand-alone ordered directive
  - Fortran: New linear clause syntax
ROCm 7.0 support
NVIDIA SDK 25.09 support
Enhanced DWARF support
Functional support for low-precision floating point (FP16 and BFloat16) for C, C++, and Fortran.

Issues or Bugs Resolved

CAST-39292 CCE 20.0.x compiler bug on GNU Scientific Library (GSL)
CAST-39199 Error with a combined SAVE + a DO loop + a BLOCK construct containing an ALLOCATABLE declaration construct
CAST-39134 integer(8) displaying 32-bit overflow related error with CCE compiler in rush_larsen_gpu_omp_fort benchmark
CAST-39116 CPE/25.09 mpif90/f77/fort and crayftn mis-handling -shared flag
CAST-38893 AFW Earth System Modeling Framework (ESMF) segfault when compiling with CCE/20.0.0
CAST-38866 CCE 20.0.0 fortran link time increase compared to CCE 19.0.0
CAST-38817 Thornado linking error with CCE 20.0.0
CAST-38802 Cray Fortran compiler in CCE 19.0.0 and CCE 18.x is failing to compile a code that is correct and was compilable with CCE 16.x and CCE 17.x
CAST-38782 CCE 20.x.x Incorrect error ftn-1195 with a particular ENUM value and ISO_C_BINDING
CAST-38775 crayftn error on unlimited polymorphic assumed rank argument
CAST-38750 CCE fortran do concurrent issue
CAST-38682 Thornado linking error with CCE 20.0.0
CAST-38461 OpenMP collapse leads to out-of-bounds access
CAST-38329 CCE 19.0.0 Fortran gives incorrect results with O2 or O3
CAST-38228 CCE 19.0.0 Fortran gives extraneous warning with -h omp
CAST-38206 HPE Cray Fortran OpenMP private variable is being shared
CAST-38117 crayftn -h sanitize=thread has false positives
CAST-38097 Woosley Heger problem cannot compile/run with CCE later than 16.0.1
CAST-38089 CCE 19.0.0 OpenMP producing wrong answer in ComputeRadialMomentsKernel in GenASiS
CAST-37847 The ftn sanitize option has problems and false positives
CAST-37719 HPE Cray Fortran compiler mishandling use of intrinsic within specification expressions
CAST-37200 Arrays of abstract data types (DV SM==0)
CAST-37071 CCE Fortran Internal error in THATMPI PIC codes
CAST-36536 llc error linking dyna3d target openmp with CCE 18.0.0 ftn on rzadams
CAST-36339 Issue with the OpenACC kernels construct
CAST-36177 HPE Cray EX Supercomputer (Base System Code) OpenACC compile time error Invalid accelerator routine parallelism
CAST-35380 CCE 17.0.0 Fortran compiler fails four smart pointers tests
CAST-35015 Global PARAMETER arrays not working with OpenACC
CAST-34641 Issue with HPE Cray Fortran and OpenACC; OpenACC directives incurs issues with HPE Cray compiler
CAST-33343 HPE Cray Fortran unlimited polymorphic assumed rank argument
CAST-33162 ftn compiler internal error on openmp target loop setting pointer to null
CAST-32041 OpenACC and OpenMP kernel optimization/serialization issue
CAST-31462 OpenACC exit data delete failure
CAST-31407 OpenMP offloading; poor performance of reduction for array elements
CAST-30651 Unable to use runtime variable in openmp thread_limit(var) clause
CAST-30331 Weak alias fails with CCE 13.0.0/14.0.0 C and OpenMP
CAST-30276 OpenMP atomic directive inside loop region

Compatibilities, incompatibilities, and differences

The fast address GPU optimization has been disabled at default (equivalent to -hacc_model=no_fast_addr). This optimization attempts to use 32-bit integers for GPU array index calculations to improve performance, but it can result in incorrect behavior if 32-bit precision is insufficient for large arrays. The optimization can be explicitly re-enabled with -hacc_model=fast_addr.
The craycc and crayCC compiler drivers now bypass the Cray PE driver and invoke CCE’s clang driver directly. As a result, Cray PE driver flags are no longer accepted by craycc and crayCC. This behavior now matches the crayftn driver, which was changed to bypass the Cray PE driver in CCE 20.0.0.
LLVM backends for unsupported targets have been removed. CCE now only provides LLVM backends for supported CPU and GPU targets (X86, AArch64, NVPTX, and AMDGPU).
Support for the AMD GPU gfx940 target has been removed.

This CCE release is supported for the following configurations:

CSM 1.7.1 and HPCM 1.15
RHEL 8.10 (x86) and RHEL 9.5 & 9.6 (x86 & aarch64) with USS 1.5.0
SLES15 SP7 & SP7 (x86 & aarch64) with USS 1.5.0
AMD GPU offloading support requires at least ROCm 7.0 (ROCm 6.x is no longer supported, SLES15 support limited to SP7)
NV SDK 25.09
GCC 14
AOCC 5.0 (x86_64 only)
Intel 2025.2.1 (x86_64 only)

Documentation

Cray Compiling Environment Release Overview (21.0.0)
Cray Fortran Reference Manual
Cray C and C++ Quick Reference
- These references are available at [Getting Started] (https://cpe.ext.hpe.com/docs/latest/getting_started/index.html)
Basic man pages: crayftn(1), craycc(1), crayCC(1), intro_openmp(7), intro_openacc(7)
Please see Clang Documentation online, or use the -help command line option for more information on using Clang.

Accessing product documentation

Access HPE documents and manpages for HPE CCE releases from:

HPE Support Center

CCE user guides (i.e., Fortran, Perftools, Cassini, Quick Reference, Release Overview, and CSM/HPCM/Apollo2000/XD2000 user guides) before CPE 24.11 can be retrieved from the HPE Support Center and the CPE Online Documentation Page. See Available publications for a complete list.

CCE and CSM/HPCM/Apollo2000/XD2000 user guides for CPE 24.11 (and later) are available at the online CPE documentation page at https://cpe.ext.hpe.com/docs/latest/index.html

To narrow search results from the HPE Support Center website, enter the publication and release number (for example, S-5212 18.0.0).

CPE installation guides for any release can be retrieve from the HPE Support Center website or the CPE online documentation site.
Release Package

All HPE Cray Programming Environment (CPE) and HPE Cray Compiling Environment (CCE) documents are included in documentation tar files provided in the release package. See Available publications for details.
Manpages

Manpages are textual help files available from the command line on HPE and HPE Cray systems. To access manpages, enter the man command followed by the name of the manpage. For more information about manpages, see the man(1) manpage by entering:
```
hostname> man man
```
Basic CCE man pages provided include crayftn(1), craycc(1), crayCC(1), intro_openmp(7), intro_openacc(7), and intro_MPI(3).

The ftn(1), cc(1), and CC(1) manpages are disambiguation manpages that provide basic introductions to the compiler environment. For information specific to the CCE Fortran compiler, see the crayftn(1) manpage. For information specific to the CCE C, C++, or UPC compiler, see the clang(1) manpage.

Alternatively, the craycc(1) and crayCC(1) manpages are aliases that redirect to the Clang C, C++, and UPC manpage.
Third-party documentation

Third-party documentation is not provided by HPE.

Additional resources

Product	Documentation Source
Clang/LLVM C and C++ compiler	Documentation for the CCE C and C++ compilers is available here, in the `clang(1)` manpage, and can be accessed by entering the `-help` command line option.
GNU compilers	Documentation for the GNU C and Fortran compilers is available here
glibc	glibc documentation is available here
GLIB	GLIB documentation is available here
RPM	RPM documentation is available here

Installing CCE

CCE is distributed as a set of RPM packages.

To use the CCE compilers, install a CCE compiler driver package. There are three CCE compiler driver packages:

cce-<version>-environment-modules contains Environment Modules modulefiles for CCE. The modulefiles rely on the CrayPE Drivers (CC, cc, and ftn) to invoke CCE compilers and automatically link with libraries from other loaded CPE modulefiles.
cce-<version>-lmod contains Lmod modulefiles for CCE. The modulefiles rely on the CrayPE Drivers (CC, cc, and ftn) to invoke CCE compilers and automatically link with libraries from other loaded CPE modulefiles.
cce-<version>-moduleless contains the CCE moduleless compiler drivers crayCC, craycc, craycxx, and crayftn. The moduleless compiler drivers invoke CCE compilers without automatically linking with libraries from loaded CPE modulefiles.

Optionally, you can install:

cce-<version>-gpu-amd to compile applications for AMD GPUs.
cce-<version>-gpu-nvidia to compile applications for NVIDIA GPUs.
cce-<version>-pgas-ofi to compile applications for PGAS on the OFI network target.
cce-<version>-doc for online documentation, including man pages.
cce-<version>-devel for compiler development.
cce-<version>-set-default to set CCE <version> as the default CCE on the system.

For a minimal installation suitable for running applications built by CCE, install only cce-<version>-runtime. Also install any GPU and PGAS packages that the application requires.

Procedure

To install CCE RPMs, use a package manager or use the rpm command. A package manager handles RPM dependencies automatically. The rpm command does not handle RPM dependencies automatically. Zypper is the recommended package manager on SLES systems. DNF is the recommended package manager on RHEL systems. For details on configuring each package manager, refer to the package manager’s documentation.

To install a package with Zypper, run:

hostname> zypper install <package_name>

To install a package with DNF, run:

hostname> dnf install <package_name>

To install an RPM with the rpm command, run:

hostname> rpm -ivh <rpm_name>.<arch>.rpm

Setting the default CCE version

To set CCE version <version> as default:

hostname> /opt/cray/pe/admin-pe/set_default_files/set_default_cce_<version>

To use CCE:

hostname> module load PrgEnv-cray

This module defines the system paths and environment variables needed to build an application using CCE for supported systems and loads and links additional libraries as required. The exact modules loaded vary depending on the system type.

To switch to the x.y.z version of CCE:

hostname> module swap cce cce/x.y.z

Note that users at sites that opt to not enable CPE by default must source $CRAY_ENABLE_PE to enable use of the CPE module environment.

Compiling and linking code

To compile and link code, always use either the ftn, cc, or CC command. Due to the multiple compiling environments potentially available on HPE systems, the craype module provides compiler drivers that forward the ftn, cc, and CC commands to the commands required by specific compilers.