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Deprecation of The Intel® Fortran Compiler Classic (ifort)

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The Greek philosopher Heraclitus is credited with the idea that the only constant in life is change. In one of the few remaining fragments of his writings, a translation says:
Everything changes and nothing remains still; and you cannot step twice into the same stream.


This idea of change is certainly true for software.  This blog discusses the deprecation notice for the Intel® Fortran Compiler Classic (ifort), and the impact to your projects utilizing ifort. I will get to the point: on Monday, November 20th, 2023 Intel announced the deprecation and eventual removal of Intel® Fortran Compiler Classic (ifort).  The deprecation notice is in the Release Notes and is included in the footnotes below.  Here are some facts to help understand this deprecation notice:

  1. "Deprecation" is not the same as "removal".  "Deprecation is the act or process of marking the feature or product as obsolete, to discourage its use and warn users that it *may* be phased out in the future, but not removing the capability immediately, so as to allow for continued compatibility for a period of time”.
  2. In addition to deprecation, Intel is advising users with this deprecation notice that our Intel® Fortran Compiler Classic (ifort), is soon to be removed, with the process starting in late 2024.  It is still available today (November 2023).  However, discontinuation and removal of this compiler is coming.
  3. Intel recommends customers move to the Intel® Fortran Compiler (ifx) for continued product support, including support of the latest Intel technologies and access to the industry-leading Fortran compiler.
  4. As the announcement states, ifort will be "discontinued" in late 2024.  Discontinuing ifort includes 2 events.  One event of discontinuation is that the Intel® Fortran Compiler Classic (ifort) will not be provided in version 2025 release, which is currently scheduled for late 2024.  At this date, the intent is that the version 2025.0 release and all future releases will no longer provide ifort in any of those released packages or repositories.  The second event in the discontinuation of ifort is the removal of ifort from downloads.  Customers with Intel® Priority Support can continue to download Intel® Fortran Compiler Classic from the Intel® Registration Center (IRC) for an additional year after ifort is no longer provided in our released packages.  This means availability of ifort to Priority customers up to late 2025.  The intent is that in late 2025 with the release of version 2026, all downloads of Intel® Fortran Compiler Classic (ifort) will be removed from IRC and all repositories for all customers.
  5. From the date of the Deprecation Notice, only critical and necessary fixes, such as security updates, may go into ifort until the date that ifort is permanently removed from all downloads.

Why the Move to Intel® Fortran Compiler (ifx)?  

I have written a number of articles, including this one from last year, and hosted a number of webinars over the years, to explain our move to ifx as our Fortran compiler.  The Intel® Fortran Compiler (ifx) is based on the Intel® Fortran Compiler Classic (ifort) frontend and runtime libraries but uses modern LLVM-based backend compiler technology.  Thus, ifx gives you all the Fortran features you know and love in ifort, like legacy DEC extensions, superior Fortran Standards support, and powerful compiler directives. Everything you expect in Intel Fortran. In addition, ifx adds new capabilities for Intel’s latest CPU and GPU products, including OpenMP TARGET and automatic DO CONCURRENT offload to Intel GPUs for additional accelerated performance.  

It is our belief that ifx is ready to assume the role as our flagship compiler.  For this reason, we have changed the default Fortran compiler in our Visual Studio integrations to be ifx for all new projects.  You can change the compiler, or select other installed versions of ifort and ifx as described by this page in our Developer Guide and Reference.


What, with this change, is in it for me and my development?

  • Faster compilation times, up to 18%, making you more productive
  • Optimizations for the latest and future Intel processors
  • Ability to accelerate your code with Intel GPUs
  • New LLVM community tools like the Santizers ( memory, address, thread) giving you the ability to find and fix memory issues and threading issues
  • Fortran 2023 and OpenMP* 5.2 and 6.0 being actively added now, latest Standards support going forward
  • Continued support for Intel® Fortran well into the future


Will I find bugs in ifx that I did not, or do not, have in ifort?

Possibly. We will not say that ifx and ifort should be 100% interchangeable.  By using the same code for the front-ends of ifort and ifx we minimize differences.  However, after the front-end everything else is unique to each compiler.  Different optimizations.  Different code generation. Perhaps even slight differences in compiler options.  To help with differences, we publish our ifort to ifx Porting Guide.  In the Porting Guide we capture differences and how to work with these differences. Make sure to bookmark this page as you begin your migration to ifx.  We have made every effort to make your transition from ifort to ifx as smooth as possible, but anytime you move from one compiler to another, or often if you move from one major version to the next for any compiler, you may encounter differences.

What do I do if I find a bug or issue in ifx, where “bug” is anything such as a new warning or error message, a runtime crash, or numerical differences?  Where do I report issues?

If you have an active Intel® Priority Support account, simply report the issue using the Online Service Center.  If you are not a Priority Support customer you can post your bug or any question to our Intel Fortran Community Forum.  Before reporting a bug, make sure you are using the most recent release or update of Intel Fortran.  You can find your version of ifort and ifx with the compiler options “-V -what” and supply this information with your report.  Because ifx is evolving rapidly, if you are not using the latest version of ifx you may be asked to upgrade.

If you are thinking "I am not ready to move to ifx anytime soon and intend to stay with ifort".  What are your options?

You now know our plans for ifort.  If you do not have an active Priority Support account, you can continue to download versions of ifort and ifx until late in calendar year 2024.  After that date, customers with active Priority Support will continue to have access to prior versions of ifort, as described in  this article on older version downloads.  In late calendar year 2025, all downloads of ifort will be removed from our repositories and Intel® Registration Center downloads.  These dates should help you decide the right time to make the switch from ifort to ifx.

Can I simply keep a copy of my Intel Fortran installer package and continue to use it for years into the future?

  1. Windows users should understand that in the future you cannot simply move a current or older version of Intel Fortran software onto systems with newer versions of Microsoft* Visual Studio or Microsoft* Windows.  Support for compiler products is for the specific versions of the OS and Visual Studio from Microsoft at the date your version was packaged.  Thus, it may not work with more modern versions of Windows or Visual Studio.  Please read your Release Notes, specifically the section on System Requirements, for the software environment needed for your older compiler.  In particularly, recent versions of Visual Studio are not compatible with our releases from mid-2023 and older: The Integrations from older compilers will not work with recent versions of VS 2022 v17.2+. It is quite possible that future updates to Microsoft Visual Studio and/or Windows may break your software installation.  Intel recommends customers move to the Intel® Fortran Compiler (ifx).
  2. For linux, a given version of Intel Fortran is validated just prior to release on specific major and minor versions of specific linux distributions.  Using any existing or older  Intel Fortran package on future versions of linux is not officially supported.  It may work, it may not.  The Release Notes and System Requirements specify support for exact distributions and versions.  These are the validated and supported versions of the OS.  In general, long-term support releases of linux distribution have shown good backwards compatibility within a reasonable number of versions.
  3. For both Windows and linux, keep in mind that from the date of this Deprecation Notice, only critical and necessary fixes, such as security updates, may go into ifort until the date that ifort is permanently removed from all downloads.    

If you are still using ifort with an older Intel® Parallel Studio XE installation

Parallel Studio XE is no longer supported.  Intel recommends customers move to The Intel® Fortran Compiler, (ifx), for continued product support, including support of the latest Intel technologies, and access to the industry-leading Fortran compiler.  We recommend moving to our most recently released products which have been updated to include recent versions of 3rd party components, which include functional and security updates.


Will my older Intel® Parallel Studio XE licenses stop working?

If you are still using ifort from an older Intel® Parallel Studio XE (PSXE) installation, those licenses are unaffected by the deprecation of ifort. 

The members of the Intel® Fortran Compiler development and support teams want to thank you and all fellow travelers for sharing our journey with ifort.  We encourage you to come along with us as we start a new journey with ifx!


DEPRECATION NOTICE:  Intel® Fortran Compiler Classic (ifort) is now deprecated and will be discontinued in late 2024. Intel recommends that customers transition now to using the LLVM-based Intel® Fortran Compiler (ifx) for continued Windows* and Linux* support, new language support, new language features, and optimizations. For more information on ifx, see the Intel® Fortran Compiler Developer Guide and Reference and the Porting Guide for ifort Users to ifx.


Author! Author!

Keep up with all the latest from the Intel Fortran team by following me on X @iCompilersRon

Ron Green #IAmIntel


Ron Green is a manager for the Intel® Fortran Compiler team. He is a customer advocate for Intel® Fortran and the larger Software and Advanced Technology Group (SATG) at Intel Corporation.  Ron is a moderator of the Intel Fortran Community Forum and is an Intel Developer Zone Black Belt Developer.  He has extensive experience as a Fortran developer and consultant in HPC for the past 30+ years and has been with Intel’s developer tools and compiler team for 15+ years.  


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Compilers, HPC, Developer Tools support. Fortran friendly.