It can vary from implementation to implementation but I believe that most use a balanced binary tree.

I would do a search and see if the implementation of malloc was modified between gcc library 2.4 to 2.6. My guess is that if the implementation of malloc changed, memory could be allocated differently using 2.6 over 2.4. You may have already had a memory bug previously using 2.4 but it did not manifest itself until the memory was allocated in some different way using the new library. Apparently somewhere code is overwriting memory in your class corrupting the private contents of the strings or corrupting the internal datastructures of malloc itself. You need to watch the memory locations for the strings to narrow down when the contents of those strings become corrupted. One clarification ... do the seg faults happen only when setting the string value or anytime you use the contents of the string ?

I understand about the proprietary requirements. Your code produces normal values for the numerator/demonimator values over the range of sigma that I you mentioned in my experiments. The only suggestion I have at this point is can you instrument your runtime statistics at a finer levels to see what portions of the your calculations could be responsible to efficiency reduction. If you find the solution it would be nice if you could post a follow-up to the thread. Good luck.

Any chance you can show your code that includes your use of the sigma function parameter ? Does your code produce the correct values ?

Being self employed means you have higher costs and have to provide benefits to yourself that are normally paid by an employer ... think medical insurance, disability insurance, life insurance, vacation, sick days, investments in hardware and software, etc. Plus, being self employed, at least in the US, you are subject to 15% self-employment tax. My rule of thumb for setting hourly rates is take your annual salary that you would receive from a normal employer for your job, add 50%, and then divide by 2000 hours (50 weeks/year * 40 hrs/week). You can adjust up or down depending up the project, the urgency of the project, the length of the project, special skills you have, etc. Generally for longer term (multi-month) contracts I generally reduce rates by about 5%. Also, for well defined projects, consider a fixed rate cost for the project. This option is usually well received by clients as they know their cost upfront. But be aware of project creep and have the contract stipulate readjustment of the fee if the client changes the spec too much, how the project will be deemed "complete", what is the final testing and acceptance procedure, and how on-going support and bug fixes are going to be handled. Someone in an earlier reply asked about how to get your first clients ... For me it has always been through a previously employer or via previous co-workers that went to other companies. So for someone considering becoming a self-employed developer trying to maintain good relationships with co-workers and former employers is a good first step as well as continuing to network with co-workers. Additionally, being a known quantity to the client can help with competing against out-sourcing to an unknown developer (or developers) in another country who may be cheaper. I have had one project that was specially due to fixing a poor inefficient (runtime and memory) implementation in a critical module written by junior/inexperienced developers from another country. Good luck. I hope this helps. ------------------------------------ Tim Moore http://www.linkedin.com/in/timothyphilipmoore