Something I do often if I'm storing a bunch of string values and I want to be able to find them in O(1) time later is: foreach (String value in someStringCollection) { someDictionary.Add(value, String.Empty); } This way, I can comfortably perform constant-time lookups on these string values later on, such as: if (someDictionary.c...
I know it's probably not the right way to structure a database but does the database perform faster if the data is put in one huge table instead of breaking it up logically in other tables? I want to design and create the database properly using keys to create relational integrity across tables but when quering, is JOIN'ing slower than ...
Are there any tools to give some sort of histogram of where most of the execution time of the program is spent at? This is for a project using c++ in visual studio 2008. ...
I need to optimize code to get room for some new code. I do not have the space for all the changes. I can not use code bank switching (80c31 with 64k). ...
I was working on some code recently and came across a method that had 3 for-loops that worked on 2 different arrays. Basically, what was happening was a foreach loop would walk through a vector and convert a DateTime from an object, and then another foreach loop would convert a long value from an object. Each of these loops would store...
I'm importing Brazilian stock market data to a SQL Server database. Right now I have a table with price information from three kind of assets: stocks, options and forwards. I'm still in 2006 data and the table has over half million records. I have more 12 years of data to import so the table will exceed a million records for sure. Now, ...
Given a NxN matrix with 0s and 1s. Set every row that contains a 0 to all 0s and set every column that contains a 0 to all 0s. For example 1 0 1 1 0 0 1 1 1 0 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 results in 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 A Microsoft Engineer told me that there is a solution that involves no extra mem...
When writing application code, it's generally accepted that premature micro-optimization is evil, and that profiling first is essential, and there is some debate about how much, if any, higher level optimization to do up front. However, I haven't seen any guidelines for when/how to optimize generic code that will be part of a library or...
I need advice regarding subselect performance in MySQL. For a reason that I can't change, I am not able to use JOIN to create quesry filter, I can only add another AND clause in WHERE. What is the peformance of: select tasks.* from tasks where some criteria and task.project_id not in (select id from project where project.is_templa...
I was reading Jeff Atwood's blog on Behold WordPress, Destroyer of CPUs and saw that many people there considered 20 SQL Queries per page load to be a lot. What is the average amount of queries per page nowadays for a highly dynamic page with auto suggest, auto refreshing of data, customized pages, and the kitchen sink? For a simple ...
I've heard that trampolining is an ineffective way of implementing TCO. How does DrScheme (PLAI Scheme, technically) do it? Does it do it the 'right' way (that is, produce assembly code which directly branches to the tail call, instead of going through the stack and trampolining)? ...
Obviously having whitespace in css, aspx and html pages is a great advantage at design time. But is there a way to (a tool that will) clear all the whitespace from all the files and possibly merge javascript and css files in a more optimal way. I am using asp.net themes so there are quite a lot of separate css files that would be impro...
Hi guys. The project I'm working on has two type of accounts, "people" and "companies". I hold a single "users" table with all the accounts and just the basic info needed for login (email, pass, etc), and two other tables "user_profiles" (regular people) and "company_profiles" (companies) that hold more specific columns for each type, bo...
I have to solve the following problem in an optimal way. Input data is: N points in a plane given as a (x, y) pair of integer coordinates M points in the same plane given as a (x, y) pair of integer coordinates representing the center of a circle. All this circles have (0, 0) on their edge. I need to find a way of isolating a number...
Are there any performance benefits to me not using the gridview in asp.net for simple tables querying from a stored procedure and instead writing the html in server code myself. I'm sure my code would certainly be more concise in output. ...
I just finished reading this post: http://developer.yahoo.com/performance/rules.html#flush and have already implemented a flush after the top portion of my page loads (head, css, top banner/search/nav). Is there any performance hit in flushing? Is there such a thing as doing it too often? What are the best practices? If I am going to h...
What is the most efficient algorithm for grouping identical items together in an array, given the following: Almost all items are duplicated several times. The items are not necessarily integers or anything else that's similarly simple. The range of the keys is not even well-defined, let alone small. In fact, the keys can be arbitrar...
Update - for those of a facetious frame of mind, you can assume that Aggregate still produces the normal result whatever function is passed to it, including in the case being optimized. I wrote this program to build a long string of integers from 0 to 19999 separate by commas. using System; using System.Linq; using System.Diagnostics; ...
I'm currently using msbuild for a solution of over 600 projects. Imagine I change the code for 1 library that is used by 10 projects. Instead of providing all 600 projects to msbuild and let it compile all of them and figure out the dependencys. I was wondering if there was a program or library I could use that would analyse the dep...
What is the most efficient way to remove duplicate items from an array under the constraint that axillary memory usage must be to a minimum, preferably small enough to not even require any heap allocations? Sorting seems like the obvious choice, but this is clearly not asymptotically efficient. Is there a better algorithm that can be d...