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Questions tagged [performance]

Performance is a subset of Optimization: performance is the goal when you want the execution time of your program or routine to be optimal.

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55
votes
3answers
3k views

Analyzing Minesweeper Probabilities

Calculating probabilities in Minesweeper might sound like an easy task, but I've seen so many probability calculators that's either incorrect, horribly slow, or with ugly code (or all of them) so I ...
27
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4answers
7k views

Sieve of Eratosthenes - Python

I've been doing a lot of Project Euler lately and just wanted to make sure my implementation was as good as it could be. Does anyone have any suggestions to speed this up? ...
11
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3answers
5k views

Project Euler Problem 12 - triangle number with 500 divisors

I've just done Problem 12 of Project Euler: What is the value of the first triangle number to have over five hundred divisors? The \$N\$'th triangle number is the sum of all natural numbers ...
32
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5answers
52k views

Brute Force Algorithm in C

This is a simple brute force algorithm that I have programmed in C. All the program does is print out every possible combination of the given alphabet for the ...
14
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1answer
8k views

Solving 15 puzzle

I'm trying to solve 15 puzzle using A* algorithm, but something really bad goes on in my get_solution() function that ruins performance. I guess there is a too much ...
34
votes
8answers
54k views

Using a for-loop or sleeping to wait for short intervals of time

I need to wait for short intervals of time in my program, but I really don't want to include unistd.h just to use sleep, so I'm ...
20
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6answers
12k views

Optimize Conway's Game of Life

I have coded up an implementation of Conway's Game of Life and I have a performance bottleneck in it which I wish to be optimized. The main logic is in the Universe ...
8
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4answers
20k views

Find the binary gap of a number N

For example, number 9 has binary representation 1001 and contains a binary gap of length 2. The number 529 has binary representation 1000010001 and contains two binary gaps: one of length 4 and one of ...
9
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2answers
10k views

How can I quickly find unique list items?

I use the loop-every-single-list-item approach to filter out unique elements in a given list, which tends to be very inefficient way as a list grow in size, or as function call frequency increases. ...
6
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3answers
2k views

Efficiency of Project Euler problem 35

The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime. There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, ...
5
votes
1answer
768 views

Recursive Breadth First Search for Knights Tour

This was written as an experiment in performance, based on another question here on CodeReview. Input into the algorithm is the number of squares on one edge of the chess board, the point of origin, ...
34
votes
6answers
5k views

Parser written in PHP is 5.6x faster than the same C++ program in a similar test (g++ 4.8.5)

I'm absolutely dumbfounded by this. I was trying to demonstrate to myself how much faster C++ is than even modern PHP. I ran a simple CSV parsing program in both that have the same output. The CSV ...
55
votes
9answers
12k views

Project Euler problem 1 in Python - Multiples of 3 and 5

I'd like suggestions for optimizing this brute force solution to problem 1. The algorithm currently checks every integer between 3 and 1000. I'd like to cut as many unnecessary calls to ...
21
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4answers
2k views

Finding the sub-array with the maximum sum - my approach

This is the code I ended up with that implements the approach I described in a recent answer to another question about the same problem The basic idea here is to not loop through more things than ...
10
votes
1answer
363 views

Sequence-based enumeration of permutations in lexicographic order

This is follow-up on On Knuth's "Algorithm L" to generate permutations in lexicographic order, where I presented the following method to enumerate all permutations of array elements in ...
5
votes
2answers
8k views

Printing longest sequence of zeroes

I am doing a coding exercise in codility and I came across this question: A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ...
5
votes
2answers
852 views

Matrix of articles and authors from large JSON dataset

Given the following JSON data containing 4 articles by 4 different authors: ...
12
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3answers
3k views

The Beauty and the Strings

This originally appeared in Facebook's hacker cup 2013. Solving it was fun, though I find myself looping through similar data quite often. Challenge: Print the maximum beauty of strings. ...
11
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3answers
2k views

Coin Change: Minimum number of coins

Problem: You are given n types of coin denominations of values \$v(1) < v(2) < ... < v(n)\$ (all integers). Assume \$v(1) = 1\$, so you can always make change for any amount of money \$C\$....
8
votes
1answer
789 views

Timing analysis of many test cases in Python

I am learning about timing analysis in Python. I used time module before it was pointed out that timeit module would be better ...
7
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4answers
543 views

MergeSort performance

Do you see any inefficient parts with the following code? On internet I see 30 ms for 100.000 integers but I can sort 100.000 integers in 300ms. The data is random. I am using late 2013 macbook pro so ...
5
votes
2answers
2k views

Generating frequency tables based on CSV dataset

I am working on a project which crunches plain text files (.lst). The name of the file names (fileName) are important because I'...
4
votes
1answer
228 views

Simple neural-network simulation in C++ (Round 2)

Intro Yesterday I posted this question. Since then, I've updated my code to incorporate these suggestions. I've also removed the dependence on C++11. Finally, I've made the following changes that ...
3
votes
2answers
732 views

Non generic Skip List implementation in C++ Version 2

Edit: This code was reworked and repostetd under a new question: Generic Skip list implementation in C++ Version 3 This is a follow up of: Non generic Skip List implementation in C++ If you don't ...
3
votes
2answers
83 views

Mixed Duo String Generator

I've create a program that finds mixed duo within a string. It removes characters from a string that do not form the first mixed duo. It does not rearrange the order of the string, it ony remove ...
11
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2answers
505 views

A Specific Combination

This code is going to be included in my Minesweeper Probabilities project. (so far it only exists on the develop-branch) The purpose is to return a specific combination, let's say for example that ...
5
votes
4answers
596 views

Class Seperation vs Polymorphism

I'm interested in optimizing my code. Can someone help me understand the best way to trim this code down with DRY methodology? So I've got these two classes here preforming WMI queries on two ...
4
votes
1answer
2k views

Simplifying and optimizing factors and prime factorization generator

My first algorithm for finding the factors of a number was pretty slow and horrible (it started at \$O(n^2)\$, where n was not even the inputted number), but I eventually came up with this new code. ...
3
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2answers
1k views

Premium palindromic primes

Challenge: Write a program which determines the largest prime palindrome less than 1000. The answer is 929, and my program correctly finds and prints this, but actually ended up being more complex ...
33
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7answers
6k views

Project Euler #7 10001st prime

I decided to start working on the Euler project exercises. I'm doing fine for now but the seventh problem is running quite slow and I can't think of anything to make it work faster. It takes around ...
15
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4answers
3k views

Sieve of Sundaram for Project Euler 7: Python implementation slower than C++ and R

A friend of mine recently started learning R, and she complained to me that R is very slow. She was working on Project Euler Problem 7, which asks for the value of the 10001st prime number. For ...
25
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3answers
107k views

Brute force password-cracker

I am just coding some classic brute force password cracking program, just to improve myself. I've explained how my program works at the start of the code. Check some of those screenshots to ...
29
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6answers
4k views

DailyProgrammer 284: Wandering Fingers

Description Software like Swype and SwiftKey lets smartphone users enter text by dragging their finger over the on-screen keyboard, rather than tapping on each letter. You'll be given ...
14
votes
1answer
642 views

Large Number Limit Extravaganza

I am writing a program that computes $$n-n \cdot \left(\prod_{i=1}^n (1-\frac{1}{p_i})\right)$$ which is rewritten in my code as: $$\left(1-\left(\prod_{i=1}^n(1-\frac{1}{p_i})\right)\right) \cdot ...
13
votes
5answers
21k views

Smallest Multiple

I just recently learned about Project Euler and have started doing the problems on there. I cleared problem 1 and 2, had no idea how to do 3 and 4, and started to do 5. I've seen the post regarding ...
8
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5answers
8k views

Sieve of Eratosthenes optimization

I have applied some optimizations like storing only odd values and starting to mark off from square of the number. Can it be optimized further? ...
23
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2answers
1k views

parcel: a JSON parsing library in C

I've created a JSON parsing library in C, and would like some feedback on it (feel free to submit a pull request on GitHub). Any and all suggestions are acceptable, but I would prefer if reviews were ...
7
votes
4answers
5k views

Hacker Rank - Poisonous Plants

I have the solution for the problem, but it is taking me 7 seconds to run on a large dataset. I am trying figure out a better way of doing this. It has to run in under 3 seconds. Problem Statement: ...
32
votes
4answers
16k views

Recording audio in C

Please note there are newer revisions of this code, one here, and one here for continuous audio recording. This is a program I wrote as a .wav audio recording library for Linux. It was developed on ...
12
votes
4answers
566 views

Solver for a number-game (8-queens applied to Sudoku)

Since I while ago I've been addicted to a number-game that you can think of as a binary Sudoku. The game is called (in Italian) Alberi (trees) and I haven't found any equivalent when searching the ...
9
votes
6answers
4k views

Sum of all primes under 2 million

I have this assignment to write the optimized space and time code for finding the sum of all primes under 2 million. I'm using the following function to check if each number is prime: ...
15
votes
3answers
2k views

On Knuth's “Algorithm L” to generate permutations in lexicographic order

I needed a method to generate all permutations of given elements, so I decided to implement "Algorithm L (Lexicographic permutation generation)" from Donald E. Knuth, "GENERATING ALL PERMUTATIONS" in ...
13
votes
1answer
7k views

Faster computation of barycentric coordinates for many points

I'm just starting to understand the Python syntax and I created a module that does what I wanted, but really slow. Here are the stats of cProfile, top 10 ordered by ...
11
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2answers
8k views

Efficiently using Apache HttpClient in multithreaded environment

I have a library which is being used by customers and they are passing DataRequest object which has userid, various ...
8
votes
1answer
2k views

Prime Number Generator in Swift

I would like to make (or improve my function) a function that returns an array of integers containing all the prime numbers from 2...n that can execute as quickly ...
4
votes
3answers
1k views

Mixin, @extend or (silent) class?

I am struggling with the basic concepts of SASS. I have a page that has multiple section, all of them are sharing properties like width, ...
2
votes
1answer
867 views

Efficiently filter a large (100gb+) csv file (v1)

EDIT: This question was followed up by this question, with improved code. I have a set of pretty large files (>2 GB, over 30m rows) containing intraday data in the following format: ...
15
votes
3answers
1k views

Wheel based unbounded sieve of Eratosthenes in Python

Answering this SO question recently, I've developed the following code (based on a well-known Active Code recipe, as discussed here): ...
12
votes
6answers
4k views

Python 3 - Fibonacci Implementation

I wrote a function returning the n-th Fibonacci number in Python 3: ...
12
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2answers
4k views

More efficient way to retrieve data from JSON

I am using the jsmn JSON parser (source code) to get extract data from a JSON string. jsmn stores the data in tokens that just point to the token boundaries in the JSON string instead of copying the ...

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