How to process a STL vector using SSE code

In C++ it's very convenient to store array data using the std::vector from the STL library. On modern CPUs you can take advantage of vectorized instructions that allow you to operate on multiple data elements at the same time. But how do you combine a std::vector with SSE code? For example, you want to sum up each element of a float vector of arbitrary length (in C++ this corresponds to std::accumulate(v.begin(), v.end(), 0.0f)). This article will show you how to access the elements of the vector using SSE intrinsics and accumulate all elements into a single value.

Fast iteration over STL vector elements

The STL class std::vector is a great container for managing dynamic arrays. Unfortunately it introduces a slight overhead when iterating through it using an index. For example, the following code is not very efficient: