csearch

버전 1.0.1 (72 KB) 작성자: Peter Cook
Fast C-MEX for Array Lookups and Masking
다운로드 수: 9
업데이트 날짜: 2019/7/29

# csearch
Fast C-MEX for Array Lookups and Masking

Suppose you need to mask indices of a large array
```
argmin = find(x>=y, 1, 'first');
argmax = find(x<=y, 1, 'last');
maskedArray = x(argmin:argmax);
```
There is considerable time savings to the masking operation if the array is presorted (e.g. an array of serial timestamps) - the algorithm is now O(log(n)) instead of O(n). For a small array this doesn't make a big difference, but for a large one it is significant. `csearch` enables you to take advantage of this property of sorted arrays to quickly mask large arrays. If you use csearch on an unsorted array, the result is undefined. The idea is based on the implementation of bsearch.c in [torvalds/linux/lib/bsearch.c](https://github.com/torvalds/linux/blob/master/lib/bsearch.c).

## Syntax
```
%CSEARCH Fast Lookup and Masking for Sorted Arrays
%
% argmax = csearch(x, 'lt', y) is equivalent to MATLAB's find(x<y, 1, 'last')
%
% argmax = csearch(x, 'le', y) is equivalent to MATLAB's find(x<=y, 1, 'last')
%
% argmin = csearch(x, 'gt', y) is equivalent to MATLAB's find(x>y, 1, 'first')
%
% argmin = csearch(x, 'ge', y) is equivalent to MATLAB's find(x>=y, 1, 'first')
%
% Class Support
% -------------
% The input array x must be a 1D finite, real, non-sparse array of
% the following classes: uint8, int8, uint16, int16, uint32, int32,
% uint64, int64, single or double.
%
%
% Notes
% -----
% 1. If input y is outside the range of the array x, -1 is returned
%
% 2. Input y should be the same class as x
%
%
% Peter Cook 2019
```

## Benchmarks
```
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
double precision
num = 100, 1000 repetitions
csearch: 0.01158909 s, MATLAB: 0.00262154 s
num = 1000, 1000 repetitions
csearch: 0.00299610 s, MATLAB: 0.00392571 s
num = 10000, 1000 repetitions
csearch: 0.00293305 s, MATLAB: 0.02520050 s
num = 100000, 1000 repetitions
csearch: 0.00387134 s, MATLAB: 0.13428660 s
num = 1000000, 1000 repetitions
csearch: 0.00318716 s, MATLAB: 1.07517482 s
num = 10000000, 1000 repetitions
csearch: 0.00379733 s, MATLAB: 14.31496315 s
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
single precision
num = 100, 1000 repetitions
csearch: 0.00319169 s, MATLAB: 0.00224358 s
num = 1000, 1000 repetitions
csearch: 0.00314525 s, MATLAB: 0.00392495 s
num = 10000, 1000 repetitions
csearch: 0.00310673 s, MATLAB: 0.02433735 s
num = 100000, 1000 repetitions
csearch: 0.00323587 s, MATLAB: 0.12829741 s
num = 1000000, 1000 repetitions
csearch: 0.00358551 s, MATLAB: 0.79688118 s
num = 10000000, 1000 repetitions
csearch: 0.00298553 s, MATLAB: 12.05700865 s
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
```

인용 양식

Peter Cook (2024). csearch (https://github.com/peterfranciscook/csearch), GitHub. 검색됨 .

MATLAB 릴리스 호환 정보
개발 환경: R2016b
모든 릴리스와 호환
플랫폼 호환성
Windows macOS Linux
카테고리
Help CenterMATLAB Answers에서 Author Block Masks에 대해 자세히 알아보기

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

GitHub 디폴트 브랜치를 사용하는 버전은 다운로드할 수 없음

버전 게시됨 릴리스 정보
1.0.1

update README.MD

1.0.0

이 GitHub 애드온의 문제를 보거나 보고하려면 GitHub 리포지토리로 가십시오.
이 GitHub 애드온의 문제를 보거나 보고하려면 GitHub 리포지토리로 가십시오.