LWN.net
reports
on changes to Python 3.13 urllib standard library.
It was deduced that Apple rejected Python 3.12 apps due to a string in the Python stdlib that was rejected, regardless of code execution.
There naturally was some very good discussion linked to in the LWN.net article that illustrates the conflict between closed commercial platforms with great financial might and open source software.
The Python 3.13 patch has already been merged.
A pull request backport
patch for Python 3.12 has also been created, and illustrates the clean nature of the patch and new configure flag.
Writing to environment files can set any environment variable.
For example, to set environment variable “CMAKE_INSTALL_PREFIX” and “CMAKE_PREFIX_PATH” to “~/libs” for the following job steps:
Note: since jobs don’t normally interact without additional options, advanced techniques would be needed to make a dynamic workflow environment variable.
HDF4
is a predecessor to the industry-standard HDF5 data file format.
This
HDF4 CMake example
we created shows how to build and link HDF4 seamlessly with Fortran example code.
Users and developers might accidentally build a program or library without optimizations when they are desired.
This could make the runtime 10 to 1000 times or more slower than it would be with optimizations.
This could be devastating in computational cost on HPC and cause needless schedule delays.
Programmatically detecting or using a heuristic to determine if a program was built with optimizations can help prevent this.
Such methods are language-specific.
CMake, NDEBUG is set if CMAKE_BUILD_TYPE is Release or RelWithDebInfo.
Meson: NDEBUG is set if buildtype is release or debugoptimized with
There is currently no universal language standard method in C / C++ to determine if optimization was used on build.
The presence of macro NDEBUG is used by the
standard library
to
disable assertions.
One could use if NDEBUG is defined as an indication if optimizations were used.
boolfs_is_optimized(){
// This is a heuristic, trusting the build system or user to set NDEBUG if optimized.
#if defined(NDEBUG)
returntrue;
#else
returnfalse;
#endif
}
If the Fortran code is compiled with preprocessing, a method using NDEBUG as above could be used.
Fortran iso_fortran_env provides functions
compiler_version
and
compiler_options.
These could be used in a fine-grained, per compiler way to determine if optimizations were used.
Distributed Python environments would virtually always be optimized.
One can use heuristic checks to help indicate if the Python executable was built in debug mode.
I am not yet aware of a universal method to determine if the CPython executable was built with optimizations.
HDF5 command line tools
h5dump and h5ls are handy to quickly explore HDF5 files from the command line.
Backup link to
old documentation.
They are particularly useful when accessing a remote computer such as HPC where the HDF5 files may be very large and would take a while to transfer to a local computer.
h5ls
provides a high-level look at objects in an HDF5 file.
Backup link to
old documentation.
Typically we start examining HDF5 files by printing the dataset hierarchy:
h5ls --recursive my.h5
Determine the filters used (e.g. was the data compressed):
h5ls --verbose my.h5
h5dump
can print the entire contents of an HDF5 file to the screen.
Backup link to
old documentation.
This can be overwhelming, so we typically print only the headers to start:
h5dump --header my.h5
Individual variables can be printed like:
h5dump --dataset=myvar my.h5
Determine the filters used (e.g. was the data compressed):
The C++ Standard Library uses size_type as a property of containers like std::vector, std::string, etc.
This is
generally recommended
over using size_t directly.
Example C++ code snippets using size_type property:
Intel oneAPI is a cross-platform toolset that covers several programming languages including C, C++, Fortran and Python.
Intel oneAPI replacesIntel Parallel Studio.
Intel oneAPI including the C++ “icpx” compiler, Fortran “ifx” compiler, and Intel MPI is free-to-use and no login is required to download oneAPI.
We suggest using the “online installer” download, which is a small download.
The “online” installer can be copied over SSH to an HPC user directory for example and installed from the Terminal.
Windows requires Visual Studio Community to be installed first–IDE integration is optional and we don’t use it.
Visual Studio integration is optional–if installed, cmake -G "Visual Studio 17 2022" can be used to generate Visual Studio project files.
On Linux, oneAPI
requires GNU GCC headers etc..
Some HPC systems have a too-old GCC version defaulting for Intel oneAPI.
This can cause problems with C++ stdlib or other linking problems.
If needed, set environment variable CXXFLAGS for
Intel GCC toolchain
if needed in custom “oneapi.sh” like:
CI runners across CI services often update software images regularly, perhaps weekly.
This can break workflows, but reflects user devices.
GitHub Actions updates the runners weekly or so.
A few times a year on average across projects and operating system this may require updating the CI YaML configuration.
Apple updates of XCode a few times a year this can disrupt end users and CI runs.
To have a version stable CI image would generally require private on-premises CI like Jenkins or GitHub Actions for on-premises.
Those on-premises CI runners then need maintenance.
The key issue with such frozen CI runners is they are out of date with what end users have.
For example, macOS with Homebrew is probably the majority of scientific computing users besides HPC.
Homebrew updates often and breaks occur across projects a few times a year.
Better to catch that in CI rather than on end user devices.