Optimization is the process of improving an existing program to make it work more efficiently or/and using less resources.

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256 views

Next power of 2 for a number (in search for better “bit-twiddling” way)

I just wonder if there exists better (i.e. faster?) way to get the next power of 2 for a given number than the following one (maybe some better sort of "bit-twiddling" hack is possible?) ... static ...
6
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4answers
4k views

How do I traverse a tree without using recursion?

I have a very large in memory node tree and need to traverse the tree. Passing the returned values of each child node to their parent node. This has to be done until all the nodes have their data ...
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3answers
731 views

Unique and primary keys on a database (mysql)

I'm having quite some doubts here... If I have a table related to username/password login how can I assure there won't be any more matches of the same username and password in the same table using ...
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2answers
660 views

Algorithm for fast tag search

The problem is the following. There's a set of simple entities E, each one having a set of tags T attached. Each entity might have an arbitrary number of tags. Total number of entities is near 100 ...
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2answers
326 views

Multi regex matching — what to do to optimize it?

I have multiple regexes matching an input in greedy-first mode. All regexes are already compiled and I don't see what I can do more to speed-up things. I mean using tools coming with .Net framework. ...
3
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1answer
292 views

Compiler doesn't inline anything?

I've rolled my own SIMD-accelerated math library. It's gotten pretty complete, so naturally I went to conduct speed tests and optimize it. Btw this isn't premature optimization, the lib is actually ...
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0answers
163 views

Understanding velocity update in Binary Particle Swarm Optimization

I am wondering how to interpret the velocity update in a Binary Particle Swarm Optimization (PSO). To recap the velocity update : V(t+1) = V(t) + c1 * r1 * (XlocalBest - X(t)) + c2 * ...
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3answers
959 views

Ordering if conditions for efficiency and clean code [closed]

This is purely a design question and the example is simple to illustrate what I am asking and there are too many permutations of more complex code to provide examples that would cover the topic. I am ...
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1answer
177 views

What are some efficient ways to set up my environment when working on a remote site?

Hello fellow Programmers, I am still a relatively new programmer and have recently gotten my first on-campus programming position. I am the sole dev responsible for 8 domains as well as 3 small sized ...
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1answer
130 views

Optimising news fetching

I have a web scraper for scraping news from different sources in wp7. My current appraoch for doing this is: load newspapers information from xml file. go to the specified sections and fetch the ...
0
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1answer
248 views

How small is the footprint of a small C compiler?

This week I could optimize using a reduced C library that allowed a drastic shrinkage in code size - from about 60 K to about 6 K and then we could load the code in the 8 K on-chip memory of an FPGA ...
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2answers
388 views

Optimizing code generation for expressions in a compiler

I don't know if this question has a simple answer or not, but I just have to ask. I'm reading this tutorial (I don't know if this is a well-known series, but it's name is 'Let's build a compiler!' by ...
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2answers
430 views

Larger Code is Still Faster

When compiling C code with gcc, there are compiler optimizations, some that limit code size and others create fast code. From the -S flag, I see that the -O2/03 generates more assembly than the -Os ...
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4answers
2k views

How to find bottlenecks in an application? [duplicate]

I'm building an application with lots of components, a lot of which are third-party so I only know what I can get from their documentation. From time to time, by pure luck, I find out one of these ...
3
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1answer
555 views

Does setting a function public affect the C# compiler's ability to inline the function as an optimization?

This could be either for the .NET or Mono compilers. I know that under certain conditions the compiler can inline functions (e.g. small, single call site, etc.) as an optimization. However, if the ...
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1answer
135 views

Optimization of time-varying parameters

I need to find an optimal set of "n" parameter values that minimize an objective function (a 2-hr simulation of a system). I have looked at genetic algorithm and simulated annealing methods, but was ...
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4answers
249 views

Which if statement requires less computation?

I have if (!b && c || a && c) //do action a else //... Due to some internal relationship between a, b, and c. !b && c || a && c is proved to be equivalent to (! ...
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1answer
181 views

Algorithm to arrange objects so that the total length of edges between them is minimized?

We are given a list of edges between a set of N vertices. There are atmost three edges joining a vertex. We have to arrange all the vertices on a straight line with the positions numbered from 1 to N ...
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2answers
616 views

What is the exact syntax of inline?

CASE 1 (Definition and declaration in same source file) Suppose both my prototype and definition of global function is in .cpp file. Where should I write inline keyword to make compiler know? In ...
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1answer
346 views

What are some algorithms that can assist with reservation time scheduling?

Here's the gist of the problem: There are multiple service providers who each have their own schedules of availability. There are multiple customers who seek their services. Customers need to be able ...
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4answers
201 views

Efficient way of evaluating an array of strings then add to an array in Ruby

I am looking for an efficient way of evaluating an array of strings against a series of rules and then adding them to another array. For example I have an array of strings: something a 1234 #gohere ...
3
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1answer
767 views

Benefits of setting PHP memory_limit to lower value for specific PHP script?

I need to execute just few lines of PHP code on every single page of my website. This PHP code does not require more than 4MB memory. That is why i want to allocate just 4MB memory to all pages by ...
3
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5answers
256 views

Premature optimization in deciding how to optimize?

We have a class that has been properly identified for optimization. We've done the profiling and testing, and it's a problem. Now we have two possible approaches for optimizing this class: There is ...
3
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3answers
226 views

Are there algorithims for polling optimization?

I have a web-application with an async HTTP backend, which gets called by the client by AJAX requests. The client has to start a job and then polls for the result. I started with a simple 150ms ...
0
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1answer
466 views

Sum of divisors of numbers of the range ~ 10^6

I was trying to find the sum of divisors of numbers upto 106. The test cases are like of the order of 105. I have done some pre processing like int divisors(int num) { int sum=0; for(int ...
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7answers
433 views

When to start thinking about scalability? [closed]

I'm having a funny but also terrible problem. I'm about to launch a new (iPhone) app. It's a turn-based multiplayer game running on my own custom backend. But I'm afraid to launch. For some reason, I ...
0
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1answer
397 views

Python — Time complexity of built-in functions versus manually-built functions in finite fields

Generally, I'm wondering about the advantages versus disadvantages of using the built-in arithmetic functions versus rolling your own in Python. Specifically, I'm taking in GF(2) finite field ...
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2answers
356 views

Structuring Access Control In Hierarchical Object Graph

I have a Folder entity that can be Moderated by users. Folders can contain other folders. So I may have a structure like this: Folder 1 Folder 2 Folder 3 Folder 4 I have to ...
3
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2answers
1k views

Are unused CSS rules so costly that they must be removed?

I have been reading various Web application optimizing articles and many of them suggest to remove unused CSS rules. Currently, I have a page which has jQueryUI css, Bootstrap CSS, Datatables CSS and ...
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3answers
371 views

Change of the complexity class through compiler optimization?

I am looking for an example where an algorithm is apparently changing its complexity class due to compiler and/or processor optimization strategies.
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4answers
128 views

Use functions inside a loop declaration

What's the best practice? This : for ($i = 0; $i < count($array); $i++) { //stuff } Or, what I usually do : $count = count($array); for($i = 0; $i < $count; $i++) { //stuff } Is it the ...
2
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2answers
111 views

Find common functionalities or functions between 2 programs

I've been facing a problem recently, in which I want to optimize two programs. For that, I wanted to create some kind of "Common Interface" which I could reuse between my two programs. However, the ...
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0answers
258 views

Optimization algorithm, how to develop this problem

I have a situation where I would like your input and think over / solve algorithm. The specs There are inventories with a specified amount of capacity. 'X (width) and Y (time)' creates ...
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6answers
915 views

Jargon to describe unnecessary running of code? [closed]

Some code works but it runs an unnecessarily large fraction of the code in many cases, though that extra code is still required sometimes. Better preprocessing, simple stoppers and conditional ...
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4answers
257 views

Write then optimise or write optimised [duplicate]

Do you write your code then optimise it? Or do you write an optimised code from the beginning. I always believe in writing optimised since I really dont like to rewrite code, But please share your ...
4
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2answers
2k views

Which code is better for branch prediction optimization?

Given branch prediction, and also the effect of compiler optimizations, which code tends to offer superior performance? Note that bRareExceptionPresent represents an uncommon condition. It is not the ...
2
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3answers
269 views

Implicit optimization versus explicit optimization

To explain what I mean, let me start with an example. Consider a deque that supports O(logn) concatenation with another deque and O(n) addition of n elements at one end. This dequeimplements a ...
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1answer
603 views

using ant colony algorithm to create cross word game [closed]

I have difficulty to learn about ant colony algorithm (ACO), I have read about generating crossword game using (genetic algorithm) GA.I Know both of GA ant ACO usually used for optimization, but my ...
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2answers
1k views

Performance and other issues with using floating point types in C++

Being interested in C++ performance programming there is one aspect I really have no clue about- and that is the implications of using floating point calculations vs doubles vs normal integer ...
3
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1answer
148 views

Can profiling be used to verify if optimization was successful?

I know that profiling is useful to identify bottlenecks and determining what parts of the code require how much time to execute. The latter isn't always very easy to track in the midst of other paths ...
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2answers
203 views

How can I plan optimization tasks in Scrum?

Recently my Scrum team has received several requests for optimizing certain parts of our code. Looking at the software with a profiler found some spots where the code could be improved. We agreed to ...
2
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1answer
116 views

Turning n-dim points into m-dim where m<n and where point-to-point distance deviation is minimized

I want to apply k-means clustering to a (sparse) adjacency graph. For this I need to assign the nodes to a position in an euclidean space. Trivially I can do this by having a space with as many ...
4
votes
4answers
235 views

What performance topics should I be aware of? [closed]

When coding performance-critical portions of code (not necessarily large, but code that gets executed a lot), what topics should I be aware of/take into account. I'm already fairly familiar with ...
3
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1answer
73 views

Expensive AOT Optimizations

I've seen it stated several times that AOT can run some more expensive optimizations that take too long to be used by a JIT. But I've never seen it stated what exactly these optimizations are. So I'm ...
4
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3answers
723 views

Is it conceivable to have millions of lists of data in memory in Python?

I have over the last 30 days been developing a Python application that utilizes a MySQL database of information (specifically about Norwegian addresses) to perform address validation and correction. ...
0
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5answers
337 views

Is comparing an OO compiler to a SQL compiler/optimizer valid?

I'm now doing a lot of SQL development at my new job where as before I was doing Object Oriented desktop app stuff. I keep running across very large scripts (thousands of lines) and wanting to ...
5
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4answers
565 views

Designing a Database Application with OOP

I often develop SQL database applications using Linq, and my methodology is to build model classes to represent each table, and each table that needs inserting or updating gets a Save() method (which ...
2
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1answer
5k views

Most efficient Implementation a Tree in C++

I need to write a tree where each element may have any number of child elements, and because of this each branch of the tree may have any length. The tree is only going to receive elements at first ...
2
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6answers
1k views

Can I get a C++ Compiler to instantiate objects at compile time

I am writing some code that has a very large number of reasonably simple objects and I would like them the be created at compile time. I would think that a compiler would be able to do this, but I ...
2
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4answers
2k views

Is using a bigger buffer useful?

I use buffer for quite a long time when I need to copy a stream or read a file. And every time I set my buffer size to 2048 or 1024, but from my point of view a buffer is like a "bucket" which ...