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In programming, memory leaks are a common issue, and it occurs when a computer uses memory but does not give it back to the operating system. Experienced programmers have the ability to diagnose a leak based on the symptoms. Some believe every undesired increase in memory usage is a memory leak, but this is not an accurate representation of a leak. Certain leaks only run for a short time and are virtually undetectable.

Memory Leak Consequences

Applications that suffer severe memory leaks will eventually exceed the memory resulting in a severe slowdown or a termination of the application.

How to Protect Code from Memory Leaks?

Preventing memory leaks in the first place is more convenient than trying to locate the leak later. To do this, you can use defensive programming techniques such as smart pointers for C++.  A smart pointer is safer than a raw pointer because it provides augmented behavior that raw pointers do not have. This includes garbage collection and checking for nulls.

If you are going to use a raw pointer, avoid operations that are dangerous for specific contexts. This means pointer arithmetic and pointer copying. Smart pointers use a reference count for the object being referred to. Once the reference count reaches zero, the excess goes into garbage collection. The most commonly used smart pointer is shared_ptr from the TR1 extensions of the C++ standard library.

Static Analysis

The second approach to memory leaks is referred to as static analysis and attempts to detect errors in your source-code. CodeSonar is one of the effective tools for detection. It provides checkers for the Power of Ten coding rules, and it is especially competent at procedural analysis. However, some might find it lagging for bigger code bases.

How to Handle a Memory Leak

For some memory leaks, the only solution is to read through the code to find and correct the error. Another one of the common approaches to C++ is to use RAII, which an acronym for Resource Acquisition Is Initialization. This approach means associating scoped objects using the acquired resources, which automatically releases the resources when the objects are no longer within scope. RAII has the advantage of knowing when objects exist and when they do not. This gives it a distinct advantage over garbage collection. Regardless, RAII is not always recommended because some situations require ordinary pointers to manage raw memory and increase performance. Use it with caution.

The Most Serious Leaks

Urgency of a leak depends on the situation, and where the leak has occurred in the operating system. Additionally, it becomes more urgent if the leak occurs where the memory is limited such as in embedded systems and portable devices.

To protect code from memory leaks, people have to stay vigilant and avoid codes that could result in a leak. Memory leaks continue until someone turns the system off, which makes the memory available again, but the slow process of a leak can eventually prejudice a machine that normally runs correctly.

 

Related:

The Five Principles of Performance

In Demand IT Skills

The original article was posted by Michael Veksler on Quora

A very well known fact is that code is written once, but it is read many times. This means that a good developer, in any language, writes understandable code. Writing understandable code is not always easy, and takes practice. The difficult part, is that you read what you have just written and it makes perfect sense to you, but a year later you curse the idiot who wrote that code, without realizing it was you.

The best way to learn how to write readable code, is to collaborate with others. Other people will spot badly written code, faster than the author. There are plenty of open source projects, which you can start working on and learn from more experienced programmers.

Readability is a tricky thing, and involves several aspects:

  1. Never surprise the reader of your code, even if it will be you a year from now. For example, don’t call a function max() when sometimes it returns the minimum().
  2. Be consistent, and use the same conventions throughout your code. Not only the same naming conventions, and the same indentation, but also the same semantics. If, for example, most of your functions return a negative value for failure and a positive for success, then avoid writing functions that return false on failure.
  3. Write short functions, so that they fit your screen. I hate strict rules, since there are always exceptions, but from my experience you can almost always write functions short enough to fit your screen. Throughout my carrier I had only a few cases when writing short function was either impossible, or resulted in much worse code.
  4. Use descriptive names, unless this is one of those standard names, such as i or it in a loop. Don’t make the name too long, on one hand, but don’t make it cryptic on the other.
  5. Define function names by what they do, not by what they are used for or how they are implemented. If you name functions by what they do, then code will be much more readable, and much more reusable.
  6. Avoid global state as much as you can. Global variables, and sometimes attributes in an object, are difficult to reason about. It is difficult to understand why such global state changes, when it does, and requires a lot of debugging.
  7. As Donald Knuth wrote in one of his papers: “Early optimization is the root of all evil”. Meaning, write for readability first, optimize later.
  8. The opposite of the previous rule: if you have an alternative which has similar readability, but lower complexity, use it. Also, if you have a polynomial alternative to your exponential algorithm (when N > 10), you should use that.

Use standard library whenever it makes your code shorter; don’t implement everything yourself. External libraries are more problematic, and are both good and bad. With external libraries, such as boost, you can save a lot of work. You should really learn boost, with the added benefit that the c++ standard gets more and more form boost. The negative with boost is that it changes over time, and code that works today may break tomorrow. Also, if you try to combine a third-party library, which uses a specific version of boost, it may break with your current version of boost. This does not happen often, but it may.

Don’t blindly use C++ standard library without understanding what it does - learn it. You look at std::vector::push_back() documentation at it tells you that its complexity is O(1), amortized. What does that mean? How does it work? What are benefits and what are the costs? Same with std::map, and with std::unordered_map. Knowing the difference between these two maps, you’d know when to use each one of them.

Never call new or delete directly, use std::make_unique and [cost c++]std::make_shared[/code] instead. Try to implement usique_ptr, shared_ptr, weak_ptr yourself, in order to understand what they actually do. People do dumb things with these types, since they don’t understand what these pointers are.

Every time you look at a new class or function, in boost or in std, ask yourself “why is it done this way and not another?”. It will help you understand trade-offs in software development, and will help you use the right tool for your job. Don’t be afraid to peek into the source of boost and the std, and try to understand how it works. It will not be easy, at first, but you will learn a lot.

Know what complexity is, and how to calculate it. Avoid exponential and cubic complexity, unless you know your N is very low, and will always stay low.

Learn data-structures and algorithms, and know them. Many people think that it is simply a wasted time, since all data-structures are implemented in standard libraries, but this is not as simple as that. By understanding data-structures, you’d find it easier to pick the right library. Also, believe it or now, after 25 years since I learned data-structures, I still use this knowledge. Half a year ago I had to implemented a hash table, since I needed fast serialization capability which the available libraries did not provide. Now I am writing some sort of interval-btree, since using std::map, for the same purpose, turned up to be very very slow, and the performance bottleneck of my code.

Notice that you can’t just find interval-btree on Wikipedia, or stack-overflow. The closest thing you can find is Interval tree, but it has some performance drawbacks. So how can you implement an interval-btree, unless you know what a btree is and what an interval-tree is? I strongly suggest, again, that you learn and remember data-structures.

These are the most important things, which will make you a better programmer. The other things will follow.

Net Neutrality

You may have heard about net neutrality over the years. Recently, the concept has gone through some changes, and many would consider its underlying principles to be in danger of corruption or dissolution. However, the technical nature of net neutrality ethics makes it difficult to understand for the layperson. Read on, and the central themes and controversies surrounding the principle will be outlined and explained for your convenience.

The Theme

Invoking an external command in Python is a two step process:

 

from subprocess import call
call(["ls","-1"])

 

Tech Life in Virginia

Virginia is known as "the birthplace of a nation,? is nicknamed the "Old Dominion" and has had 3 capital cities, Jamestown, Williamsburg, and Richmond. The state motto is "Sic Semper Tyrannis"??Thus always to tyrants? More people work for the U.S. government than any other industry in this region. Virginia's largest private employer is also the world's largest ship building yard. Because the state hosts some major Net firms such as AOL, Network Solutions, and MCI WorldCom it has dubbed itself the "Internet Capital of the world".
We learn more by looking for the answer to a question and not finding it than we do from learning the answer itself. ~ Lloyd Alexander
other Learning Options
Software developers near Washington D C have ample opportunities to meet like minded techie individuals, collaborate and expend their career choices by participating in Meet-Up Groups. The following is a list of Technology Groups in the area.
Fortune 500 and 1000 companies in Virginia that offer opportunities for IBM developers
Company Name City Industry Secondary Industry
Brink's Inc. Richmond Business Services Security Services
Federal Home Loan Mortgage Corporation (Freddie Mac) Mc Lean Financial Services Lending and Mortgage
General Dynamics Corporation Falls Church Manufacturing Aerospace and Defense
CarMax, Inc. Henrico Retail Automobile Dealers
NVR, Inc. Reston Real Estate and Construction Construction and Remodeling
Gannett Co., Inc. Mc Lean Media and Entertainment Newspapers, Books and Periodicals
Smithfield Foods, Inc. Smithfield Manufacturing Food and Dairy Product Manufacturing and Packaging
ManTech International Corporation Fairfax Computers and Electronics IT and Network Services and Support
DynCorp International Falls Church Manufacturing Aerospace and Defense
Genworth Financial, Inc. Richmond Financial Services Insurance and Risk Management
MeadWestvaco Corporation Richmond Manufacturing Paper and Paper Products
Dollar Tree, Inc. Chesapeake Retail Department Stores
Alpha Natural Resources, Inc. Abingdon Agriculture and Mining Mining and Quarrying
SRA International, Inc. Fairfax Business Services Business Services Other
NII Holdings, Inc. Reston Telecommunications Wireless and Mobile
Dominion Resources, Inc. Richmond Energy and Utilities Gas and Electric Utilities
Norfolk Southern Corporation Norfolk Transportation and Storage Freight Hauling (Rail and Truck)
CACI International Inc. Arlington Software and Internet Data Analytics, Management and Storage
Amerigroup Corporation Virginia Beach Financial Services Insurance and Risk Management
Owens and Minor, Inc. Mechanicsville Healthcare, Pharmaceuticals and Biotech Personal Health Care Products
Advance Auto Parts, Inc Roanoke Retail Automobile Parts Stores
SAIC Mc Lean Software and Internet Software
AES Corporation Arlington Energy and Utilities Gas and Electric Utilities
Capital One Financial Corporation Mc Lean Financial Services Credit Cards and Related Services
Sunrise Senior Living, Inc. Mc Lean Healthcare, Pharmaceuticals and Biotech Residential and Long-Term Care Facilities
Computer Sciences Corporation Falls Church Software and Internet Software
Altria Group, Inc. Richmond Manufacturing Manufacturing Other
Northrop Grumman Corporation Falls Church Manufacturing Aerospace and Defense
Alliant Techsystems Inc. Arlington Manufacturing Aerospace and Defense
Markel Corporation Glen Allen Financial Services Insurance and Risk Management

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A successful career as a software developer or other IT professional requires a solid understanding of software development processes, design patterns, enterprise application architectures, web services, security, networking and much more. The progression from novice to expert can be a daunting endeavor; this is especially true when traversing the learning curve without expert guidance. A common experience is that too much time and money is wasted on a career plan or application due to misinformation.

The Hartmann Software Group understands these issues and addresses them and others during any training engagement. Although no IT educational institution can guarantee career or application development success, HSG can get you closer to your goals at a far faster rate than self paced learning and, arguably, than the competition. Here are the reasons why we are so successful at teaching:

  • Learn from the experts.
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    2. Our educators have years of consulting and training experience; moreover, we require each trainer to have cross-discipline expertise i.e. be Java and .NET experts so that you get a broad understanding of how industry wide experts work and think.
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