Eigen is a C++ template library for linear algebra: matrices, vectors, numerical solvers, and related algorithms.

opencv安装实录附十几行C++实现的一个人脸识别demo - 良知犹存 - 博客园

OpenCV的全称是Open Source Computer Vision Library，是一个跨平台的计算机视觉库。OpenCV是由Intel公司发起并参与开发，以BSD许可证授权发行，可以在商业和研究领域中免费使用。OpenCV可用于开发实时的图像处理、计算机视觉以及模式识别程序……Eigen库未安装。执行命令：sudo apt-get install libeigen3-dev 进行安装。

Benchmark - Eigen

Here is the list of the libraries included in the following benchmarks: [Intel发起的OpenCV为啥不用INTEL_MKL呢？]

• eigen3: ourselves, with the default options (SSE2 vectorization enabled).
• eigen2: the previous stable version of Eigen, with the default options (SSE2 vectorization enabled).
• INTEL_MKL: The Intel Math Kernel Library, which includes a BLAS/LAPACK (11.0). Closed-source.
• ACML: The AMD's core math library, which includes a BLAS/LAPACK (4.2.0). Closed-source. [我是第一次听说这个]
• GOTO: The GOTO BLAS library (2-1.13). This library have been compiled by hand specifically for the penryn architecture.
• ATLAS: The math-atlas BLAS library (3.8.3). This library has been compiled by hand specifically for the penryn architecture.

Eigen is fast.

• Expression templates allow intelligently removing temporaries and enable lazy evaluation, when that is appropriate.
• Explicit vectorization is performed for SSE 2/3/4, AVX, AVX2, FMA, AVX512, ARM NEON (32-bit and 64-bit), PowerPC AltiVec/VSX (32-bit and 64-bit), ZVector (s390x/zEC13) SIMD instruction sets, and since 3.4 MIPS MSA with graceful fallback to non-vectorized code.
• Fixed-size matrices are fully optimized: dynamic memory allocation is avoided, and the loops are unrolled when that makes sense.
• For large matrices, special attention is paid to cache-friendliness.

Eigen is versatile.

• It supports all matrix sizes, from small fixed-size matrices to arbitrarily large dense matrices, and even sparse matrices.
• It supports all standard numeric types, including std::complex, integers, and is easily extensible to custom numeric types.
• It supports various matrix decompositions and geometry features.
• Its ecosystem of unsupported modules provides many specialized features such as non-linear optimization, matrix functions, a polynomial solver, FFT, and much more.

没用过，纯转载。