Simple read vs write boolean variable performance comparison question

Question

What should be the preferred way by programmers:

1) Only Write:

SomeBoolean = True

2) Read but write only if necessary

If Not SomeBoolean Then SomeBoolean = True

Answer 1

Assuming you are referring to a RUNTIME context and a shared variable:

In a multiprocessor environment, unnecessary writes can lead to performance degradation: cache flush, synchronization overhead etc.

So YES it can make a difference... get profiling if the situation lends itself to it.

Answer 2

The difference is negligible. You will see performance differences when reading and writing files to the drive, but program performance is measured in big O. Read:

BIG O notation

Especially in VB you will not see a difference.

Answer 3

It's really hard to know the answer to this without knowing more about the environment. It seems a reasonable check would be to run some performance tests by iterating over this task many, many times.

Empirical evidence sometimes is surprising compared to what you'd expect.

Answer 4

1) will be maybe a few nanoseconds faster. I suspect that compared to other things going on in your code, that difference is nanoscopic.

On the other hand, I usually write (2) if I might want to do something else when I know that I'm actually changing the boolean. That gives me a place to do it.