speed of Arrays vs. Vectors (C++)

[Disinterred]

I am trying to write a particle simulation. I have a particles class which has member arrays to hold the information for the set of particles.

The problem is that I now want to use 3D arrays (or 3D vectors) whose dimensions will be specified through command line arguments when a user runs the program. I have not found a way to initialize a 3D array (in a constructor) with the dimensions given at the command line, so I thought I should switch to using vectors.

Will there be a huge performance decrease if I make this switch? I am very concerned with speed since these vectors will be holding 10,000 -> 1,000,000 elements and I will be calculating different things with them.

Thanks
Disinterred

[Rubberman]

The STL (Standard Template Library) classes are extensively used by major physics research and data analysis applications. My wife is a staff physicist at Fermi National Laboratory (PhD in HEP), working in the computing division to develop and maintain the software that FermiLab and CERN use for particle physics research. I doubt very much that they would hesitate for a second to use vector classes for this sort of purpose. As for performance, resizing them has the biggest impact, so creating them with the sizes you need initially will have a big impact on minimizing negative performance effects.

[Disinterred]

Thank you for your reply Rubberman! I will definitely switch to vectors now .

[Rubberman]

A lot of work has gone into optimizing the STL for performance purposes. These days, unless I have to write pure C code (kernel modules and such), I stick with STL classes, and have not been disappointed. There are times when a custom class is appropriate and preferable to STL classes, but those are not the most common situation.

[sjc06007]

@Disinterred: Would you mind posting (some) code so I can learn how you work with vectors in three dimensions?

Thanks!