Re: [boost] interest in structure of arrays container?

Subject: Re: [boost] interest in structure of arrays container?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2016-10-15 17:06:04

On 10/15/2016 03:14 AM, Michael Marcin wrote:
[snip]
 >
 > Arrays of Structures is the normal programming model.
 >
 > Let's take a toy example, say I'm looking at some census data and have a
 > structure that looks like:
 >
 > struct citizen_t {
 >     string first_name;
 >     string last_name;
 >     int salary;
 >     int age;
 > };
 >
 > Then the Array of Structures container would be:
 > vector<citizen_t> aos_citizens;
 >
 > The Structure of Arrays version of the same data would look like:
 >
 > struct soa_citizens_t {
 >     vector<string> first_names;
 >     vector<string> last_names;
 >     vector<int> salary;
 >     vector<int> age;
 > };
 >
 > soa_citizens_t soa_citizens;
[snip]
 > // Structures of Arrays
 > int avg = 0;
 > int t = 1;
 > for ( int salary : soa_citizens.salary ) {
 >     avg += (salary  - avg) / t;
 >     ++t;
 > }
 >
 >
To generalize, what about:

   template<std::size_t N, typename... Fields>
   using soa_citizens_t=
     std::tuple
     < std::array<N,Fields>...
     >
     ;

? Then wouldn't:

   std::size_t n=5;
   soa_citizens_t<n,string,string,int,int> soa_citizens;
   int avg = 0;
   int t = 1;
   std::size_t const salary=2
   for( int salary: get<salary>(soa_citizens)) {
     avg += (salary  - avg) / t;
     ++t;
   }

calculate the same thing as the avg in your example?
(CONFESSION: Not tested).

-regards,
Larry