YASK--Yet Another Stencil Kit
YASK is a framework to rapidly create high-performance stencil code including optimizations and features such as
- Support for boundary layers and staggered-grid stencils.
- Vector-folding to increase data reuse via non-traditional data layout.
- Multi-level OpenMP parallelism to exploit multiple cores and threads.
- Scaling to multiple sockets and nodes via MPI with overlapped communication and compute.
- Spatial tiling with automatically-tuned block sizes.
- Temporal tiling in multiple dimensions to further increase cache locality.
- APIs for C++ and Python.
YASK contains a domain-specific compiler to convert stencil-equation specifications to SIMD-optimized code for Intel(R) Xeon Phi(TM) and Intel(R) Xeon(R) processors.
Supported Platforms and Processors:
- 64-bit Linux.
- Intel(R) Xeon(R) processors supporting the AVX, AVX2, or CORE_AVX512 instruction sets.
- Intel(R) Xeon Phi(TM) x200-family processors supporting the MIC_AVX512 instruction set.
- Intel(R) Xeon Phi(TM) x100-family coprocessors supporting the Knights-Corner instruction set (no longer tested).
- Intel(R) Parallel Studio XE Cluster Edition for Linux
for multi-socket and multi-node operation or
Intel(R) Parallel Studio XE Composer Edition for C++ Linux
for single-socket only
(2020.1.217, a.k.a. 188.8.131.52, or later recommended).
- There was an issue in Intel(R) MPI versions 2019u1 and 2019u2 that
caused the application to crash when allocating very
large shared-memory (shm) regions, so you may have to
-no-use_shm option with these versions.
This issue was resolved in MPI version 2019u3.
- There was an issue in the Intel(R) C++ compiler 2019.1.0 that caused
an internal error when building YASK kernels.
This has been fixed in 19.1.1.x and later versions.
- If you are using the Intel(R) C++ compiler with g++ version 8.x or later,
Intel(R) C++ version 2019 or later is required.
- Building a YASK kernel with clang or the "nextgen" Intel(R) C++
compiler is possible; however,
SIMD operations for functions such as sin() are not supported in the nextgen
compiler at this time. Also, the Python interface may not work with
the nextgen compiler.
- Building a YASK kernel with the Gnu C++ compiler is possible.
Limited testing with g++ 8.2.0 shows the "iso3dfd" kernel
runs about 30% slower compared to the same kernel built with
the Intel C++ compiler.
Older Gnu C++ compilers can produce kernels that run
many times slower.
- Gnu C++ compiler, g++ (4.9.0 or later; 9.1.0 or later recommended).
Even when using Intel compilers, they rely on functionality provided by a g++ installation.
- Linux libraries
- Perl (5.010 or later).
- Gnu make.
- Bash shell.
- Numactl utility.
- Optional utilities and their purposes:
gindent utility, used automatically during the build process
to make the generated code easier for humans to read.
You'll get a warning when running
make if one of these doesn't exist.
Everything will still work, but the generated code will be difficult to read.
Reading the generated code is only necessary for debug or curiosity.
- SWIG (3.0.12 or later; 4.0.0 or later recommended),
http://www.swig.org, for creating the Python interface.
- Python 2 (2.7.5 or later) or 3 (3.6.1 or later),
https://www.python.org/downloads, for creating and using the Python interface.
- Doxygen (1.8.11 or later),
http://doxygen.org, for creating updated API documentation.
If you're not changing the API documentation, you can view the existing documentation
at the link at the top of this page.
- Graphviz (2.30.1 or later),
http://www.graphviz.org, for rendering stencil diagrams.
- Intel(R) Software Development Emulator,
for functional testing if you don't have native support for any given instruction set.
- Version 3.05.00 changed the default setting of
-no-use_shm to disable shared-memory inter-rank communication.
- Version 3.04.00 changed the terms "pack" and "pass" to "stage", which may affect
user-written result parsers. Option
auto_tune_each_pass changed to
- Version 3.01.00 moved the
-msg_rank options from the kernel
library to the kernel utility, so those options may no longer be set via
yk_solution::apply_command_line_options(). APIs to set the corresponding
options are now in
yk_env. This allows configuring the debug output
yk_solution is created.
- Version 3.00.00 was a major release with a number of backward-compatibility notices:
- The old (v1 and v2) internal DSL that used undocumented types such as
GridValue and undocumented macros such as
MAKE_GRID was replaced with an expanded version of the documented YASK
compiler API. Canonical v2 DSL code should still work using the
Soln.hpp backward-compatibility header file. To convert v2 DSL code
to v3 format, use the
Conversion is recommended.
- For both the compiler and kernel APIs, all uses of the term "grid" were
changed to "var". (Historically, early versions of YASK allowed only
variables whose elements were points on the domain grid, so the terms
were essentially interchangeable. Later, variables became more flexible.
They could be defined with a subset of the domain dimensions, include
non-domain or "miscellaneous" indices, or even be simple scalar values,
so the term "grid" to describe any variable became inaccurate. This
change addresses that contradiction.) Again, backward-compatibility
features in the API should maintain functionality of v2 DSL and kernel
- The default strings used in the kernel library and filenames to identify
the targeted architecture were changed from Intel CPU codenames to
[approximate] instruction-set architecture (ISA) names "avx512", "avx2",
"avx", "knl", "knc", or "intel64". The YASK targets used in the YASK
compiler were updated to be consistent with this list.
- The "mid" (roughly, median) performance results are now the first
ones printed by the
- In general, any old DSL and kernel code or user-written output-parsing
scripts that use any undocumented files, data, or types may have to be
- Version 2.22.00 changed the heuristic to determine vector-folding sizes when some
sizes are specified. This did not affect the default folding sizes.
- Version 2.21.02 simplified the example 3-D stencils (
to calculate simple averages like those in the MiniGhost benchmark.
This reduced the number of floating-point operations but not the number of points read for each stencil.
- Version 2.20.00 added checking of the step-dimension index value in the
yk_grid::get_element() and similar APIs.
Previously, invalid values silently "wrapped" around to valid values.
Now, by default, the step index must be valid when reading, and the valid step indices are updated when writing.
The old behavior of silent index wrapping may be restored via
The default for all
strict_indices API parameters is now
true to catch more programming errors and
increase consistency of behavior between "set" and "get" APIs.
Also, the advanced
share_storage() APIs have been replaced with
- Version 2.19.01 turned off multi-pass tuning by default. Enable with
- Version 2.18.03 allowed the default radius to be stencil-specific and changed the names of example stencil "9axis" to "3axis_with_diags".
- Version 2.18.00 added the ability to specify the global-domain size, and it will calculate the local-domain sizes from it.
There is no longer a default local-domain size.
Output changed terms "overall-problem" to "global-domain" and "rank-domain" to "local-domain".
- Version 2.17.00 determined the host architecture in
bin/yask.sh and number of MPI ranks in
This changed the old behavior of
make defaulting to
snb architecture and
Those options are still available to override the host-based default.
- Version 2.16.03 moved the position of the log-file name to the last column in the CSV output of
- Version 2.15.04 required a call to
yc_grid::set_dynamic_step_alloc(true) to allow changing the
allocation in the step (time) dimension at run-time for grid variables created at YASK compile-time.
- Version 2.15.02 required all "misc" indices to be yask-compiler-time constants.
- Version 2.14.05 changed the meaning of temporal sizes so that 0 means never do temporal blocking and 1 allows blocking within a single time-step for multi-pack solutions. The default setting is 0, which keeps the old behavior.
- Version 2.13.06 changed the default behavior of the performance-test utility (
yask.sh) to run trials for a given amount of time instead of a given number of steps. As of version 2.13.08, use the
-trial_time option to specify the number of seconds to run. To force a specific number of trials as in previous versions, use the
- Version 2.13.02 required some changes in perf statistics due to step (temporal) conditions. Both text output and
yk_stats APIs affected.
- Version 2.12.00 removed the long-deprecated
== operator for asserting equality between a grid point and an equation. Use
- Version 2.11.01 changed the plain-text format of some of the performance data in the test-utility output. Specifically, some leading spaces were added, SI multipliers for values < 1 were added, and the phrase "time in" no longer appears before each time breakdown. This may affect some user programs that parse the output to collect stats.
- Version 2.10.00 changed the location of temporary files created during the build process. This will not affect most users, although you may need to manually remove old
- Version 2.09.00 changed the location of stencils in the internal DSL from
.cpp files. See the notes in https://github.com/intel/yask/releases/tag/v2.09.00 if you have any new or modified code in