xsimd | SIMD intrinsics and parallelized , optimized mathematical
kandi X-RAY | xsimd Summary
kandi X-RAY | xsimd Summary
SIMD (Single Instruction, Multiple Data) is a feature of microprocessors that has been available for many years. SIMD instructions perform a single operation on a batch of values at once, and thus provide a way to significantly accelerate code execution. However, these instructions differ between microprocessor vendors and compilers. xsimd provides a unified means for using these features for library authors. Namely, it enables manipulation of batches of numbers with the same arithmetic operators as for single values. It also provides accelerated implementation of common mathematical functions operating on batches. You can find out more about this implementation of C++ wrappers for SIMD intrinsics at the The C++ Scientist. The mathematical functions are a lightweight implementation of the algorithms used in boost.SIMD.
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QUESTION
I am a newbie in c++, and heard that libraries like eigen, blaze, Fastor and Xtensor with lazy-evaluation and simd are fast for vectorized operation.
I measured the time collapsed in some doing basic numeric operation by the following function:
(Fastor)
...ANSWER
Answered 2020-Oct-11 at 10:40The reason the Numpy implementation is much faster is that it does not compute the same thing as the two others.
Indeed, the python version does not read z
in the expression np.sin(x) * np.cos(x)
. As a result, the Numba JIT is clever enough to execute the loop only once justifying a factor of 100 between Fastor and Numba. You can check that by replacing range(100)
by range(10000000000)
and observing the same timings.
Finally, XTensor is faster than Fastor in this benchmark as it seems to use its own fast SIMD implementation of exp/sin/cos while Fastor seems to use a scalar implementation from libm justifying the factor of 2 between XTensor and Fastor.
Answer to the update:
Fastor/Xtensor performs really bad in exp, sin, cos, which was surprising.
No. We cannot conclude that from the benchmark. What you are comparing is the ability of compilers to optimize your code. In this case, Numba is better than plain C++ compilers as it deals with a high-level SIMD-aware code while C++ compilers have to deals with a huge low-level template-based code coming from the Fastor/Xtensor libraries. Theoretically, I think that it should be possible for a C++ compiler to apply the same kind of high-level optimization than Numba, but it is just harder. Moreover, note that Numpy tends to create/allocate temporary arrays while Fastor/Xtensor should not.
In practice, Numba is faster because u
is a constant and so is exp(u)
, sin(u)
and cos(u)
. Thus, Numba precompute the expression (computed only once) and still perform the sum in the loop. The following code give the same timing:
QUESTION
ANSWER
Answered 2019-Aug-11 at 17:07According to this github issue that I have opened
-mavx2
and -ffast-math
flags should be enabled!
QUESTION
Is it possible to install ansible galaxy using brew on mac os? I tried:
...ANSWER
Answered 2018-Nov-21 at 22:59Once you install ansible on your machine using brew or pip you will get ansible-galaxy automatically it's not a package it's a subcommand of the ansible like ansible-vault ansible-doc etc.
QUESTION
I was trying out xtensor-python and started by writing a very simple sum function, after using the cookiecutter setup and enabling SIMD intrinsics with xsimd.
...ANSWER
Answered 2017-Nov-23 at 10:55wow this is a coincidence! I am working on exactly this speedup!
xtensor's sum is a lazy operation -- and it doesn't use the most performant iteration order for (auto-)vectorization. However, we just added a evaluation_strategy
parameter to reductions (and the upcoming accumulations) which allows you to select between immediate
and lazy
reductions.
Immediate reductions perform the reduction immediately (and not lazy) and can use a iteration order optimized for vectorized reductions.
You can find this feature in this PR: https://github.com/QuantStack/xtensor/pull/550
In my benchmarks this should be at least as fast or faster than numpy. I hope to get it merged today.
Btw. please don't hesitate to drop by our gitter channel and post a link to the question, we need to monitor StackOverflow better: https://gitter.im/QuantStack/Lobby
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Install xsimd
A package for xsimd is available on the Spack package manager.
You can directly install it from the sources with cmake:.
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