Eigen  3.4.90 (git rev 67eeba6e720c5745abc77ae6c92ce0a44aa7b7ae)
Benchmark of dense decompositions

This page presents a speed comparison of the dense matrix decompositions offered by Eigen for a wide range of square matrices and overconstrained problems.

For a more general overview on the features and numerical robustness of linear solvers and decompositions, check this table .

This benchmark has been run on a laptop equipped with an Intel core i7 @ 2,6 GHz, and compiled with clang with AVX and FMA instruction sets enabled but without multi-threading. It uses single precision float numbers. For double, you can get a good estimate by multiplying the timings by a factor 2.

The square matrices are symmetric, and for the overconstrained matrices, the reported timmings include the cost to compute the symmetric covariance matrix $$A^T A$$ for the first four solvers based on Cholesky and LU, as denoted by the * symbol (top-right corner part of the table). Timings are in milliseconds, and factors are relative to the LLT decomposition which is the fastest but also the least general and robust.

solver/size 8x8 100x100 1000x1000 4000x4000 10000x8 10000x100 10000x1000 10000x4000
LLT0.050.425.83374.556.79 *30.15 *236.34 *3847.17 *
LDLT0.07 (x1.3)0.65 (x1.5)26.86 (x4.6)2361.18 (x6.3)6.81 (x1) *31.91 (x1.1) *252.61 (x1.1) *5807.66 (x1.5) *
PartialPivLU0.08 (x1.5)0.69 (x1.6)15.63 (x2.7)709.32 (x1.9)6.81 (x1) *31.32 (x1) *241.68 (x1) *4270.48 (x1.1) *
FullPivLU0.1 (x1.9)4.48 (x10.6)281.33 (x48.2)-6.83 (x1) *32.67 (x1.1) *498.25 (x2.1) *-
HouseholderQR0.19 (x3.5)2.18 (x5.2)23.42 (x4)1337.52 (x3.6)34.26 (x5)129.01 (x4.3)377.37 (x1.6)4839.1 (x1.3)
ColPivHouseholderQR0.23 (x4.3)2.23 (x5.3)103.34 (x17.7)9987.16 (x26.7)36.05 (x5.3)163.18 (x5.4)2354.08 (x10)37860.5 (x9.8)
CompleteOrthogonalDecomposition0.23 (x4.3)2.22 (x5.2)99.44 (x17.1)10555.3 (x28.2)35.75 (x5.3)169.39 (x5.6)2150.56 (x9.1)36981.8 (x9.6)
FullPivHouseholderQR0.23 (x4.3)4.64 (x11)289.1 (x49.6)-69.38 (x10.2)446.73 (x14.8)4852.12 (x20.5)-
JacobiSVD1.01 (x18.6)71.43 (x168.4)--113.81 (x16.7)1179.66 (x39.1)--
BDCSVD1.07 (x19.7)21.83 (x51.5)331.77 (x56.9)18587.9 (x49.6)110.53 (x16.3)397.67 (x13.2)2975 (x12.6)48593.2 (x12.6)

*: This decomposition do not support direct least-square solving for over-constrained problems, and the reported timing include the cost to form the symmetric covariance matrix $$A^T A$$.

Observations:

The above table has been generated by the bench/dense_solvers.cpp file, feel-free to hack it to generate a table matching your hardware, compiler, and favorite problem sizes.