Then there's the danger of virtual memory. Your software will run 100 to 1,000 times slower if the computer runs out of RAM and starts swapping out to disk. Virtual memory is great in theory, but slower than sludge in practice. Programmers today need to recognize that RAM is still precious. If they don't, the software that runs quickly during development will slow to a crawl when the crowds show up. Your work simply won't scale. These days, everything is about being able to scale. Manage your memory before your software or service falls apart.
Computer networks are slow
The marketing folks selling the cloud like to pretend the cloud is a kind of computing heaven where angels move data with a blink. If you want to store your data, they're ready to sell you a simple Web service that will provide permanent, backed-up storage and you won't need to ever worry about it.
They may be right in that you might not need to worry about it, but you'll certainly need to wait for it. All traffic in and out of computers takes time. Computer networks are drastically slower than the traffic between the CPU and the local disk drive.
Programming graybeards grew up in a time when the Internet didn't exist. FidoNet would route your message by dialing up another computer that might be closer to the destination. Your data would take days to make its way across the country, squawking and whistling through modems along the way. This painful experience taught them that the right solution is to perform as much computation as you can locally and write to a distant Web service only when everything is as small and final as possible. Today's programmers can take a tip from these hard-earned lessons of the past by knowing, like the programming graybeards, that the promises of cloud storage are dangerous and should be avoided until the last possible millisecond.
Compilers have bugs
When things go haywire, the problem more often than not resides in our code. We forgot to initialize something, or we forgot to check for a null pointer. Whatever the specific reason, every programmer knows, when our software falls over, it's our own dumb mistake -- period.
As it turns out, the most maddening errors aren't our fault. Sometimes the blame lies squarely on the compiler or the interpreter. While compilers and interpreters are relatively stable, they're not perfect. The stability of today's compilers and interpreters has been hard-earned. Unfortunately, taking this stability for granted has become the norm.
It's important to remember they too can be wrong and consider this when debugging the code. If you don't know it could be the compiler's fault, you can spend days or weeks pulling out your hair. Old programmers learned long ago that sometimes the best route for debugging an issue involves testing not our code but our tools. If you put implicit trust in the compiler and give no thought to the computations it is making to render your code, you can spend days or weeks pulling out your hair in search of a bug in your work that doesn't exist. The young kids, alas, will learn this soon enough.
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