What\'s the Fastest C Library for Generating Permutations and Combinations?

Library Function for Permutation and Combination in C

Question:

What is the most frequently utilized C library to generate all combinations and permutations of k elements from a set of n elements?

Answer:

Several C libraries provide functions for calculating permutations and combinations. However, based on the analysis conducted by Charles Bailey, the following options stand out:

• Solution C: This algorithm, derived from the N2639 paper, performs efficiently, visiting each combination in 85.3531 ns.
• Solution D: The for_each_combination function from the referenced solution excels in performance, visiting each combination in just 6.62765 ns, making it over 12 times faster than Solution C and over 9000 times faster than Solution B.

Note:

The provided benchmarks were conducted on a 2.8 GHz Intel Core i5 using clang -O3 and measured the performance for generating permutations of 100 elements taken 5 at a time (resulting in over 75 million total combinations).

Although Solution C and D share similarities with Solution A, they avoid the infinite loop issue found in Solution A, resulting in accurate results. Solution D stands out as the most efficient algorithm known to Charles Bailey for visiting all combinations.

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