Performance comparison Integer Multidimensional array vs Array of Structures

Question

Are multidimensional arrays better than an array of structures if there's only one datatype? For example would an array of:

struct data{
    short datapointa;
    short datapointb;
    short datapointc;
}

be better than

short data[100][100][100][100];

What if there are several datatypes, would several arrays be better than an array of struct?

Martin Beckett · Accepted Answer · 2011-01-27 16:21:25Z

2

1, Measure it

2, You need to look at what the compiler actually generates as code, then consider things like the size of cache and number of cores.

3, Then measure it

There is very little point thinking about micro-optimizations until you have measured if the speed is a problem and if there is any difference in speed.

answered Jan 27, 2011 at 16:21

Martin Beckett

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1 Comment

Eugene Over a year ago

It doesn't seem that there is a definite answer, so I'll try structs and then the multidimensional array.

Paul R · Accepted Answer · 2011-01-27 16:21:43Z

1

It will depend mainly on your access pattern. You should choose whichever data structure gives you best locality of access - ideally you should be accessing memory contiguously, in order to make best use of cache and minimise memory bus traffic. Obviously this will depend on what kind of algorithm(s) you are using with these data structures and to some extent how you implement these algorithm(s).

answered Jan 27, 2011 at 16:21

Paul R

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1 Comment

Martin Beckett Over a year ago

Unless most of your algorithms access only one field and a single field fits in the cache and the entire array doesn't.

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