Re: [Discuss-gnuradio] ANCI-C vs Gnuradio/C++ speeeed

[Eric Blossom]

On Fri, May 12, 2006 at 07:23:10PM -0400, Achilleas Anastasopoulos wrote:
> Ilia,
> 
> I did profile two versions of the code (one with ANCI-C
> and another with C++ STL <vector>).
> It seems that the bottleneck is in accessing <vector>
> elements which is more expensive than accessing simple
> array elements.
> 
> As an example
> vector<int> x;
> x[10];
> 
> is much slower than
> 
> int *y;
> y[10]
> 
> 
> The reason i started with <vector> was the clean way that
> these were instantiated, etc.
> 
> Anyway, I am now reimplementing the code without using <vector>;
> will get back to you on this.

Achilleas, I think you're barking up the wrong tree.

There's no reason that reading or writing

  x[foo]

should be slower than

  y[foo]

particularly in a loop.  The compiler will load the underlying pointer
into a register and perform a simple indexed load or store.

If you're so inclined, 

  objdump -d example.o

or

  objdump -d example

will show you disassembled code.

Eric