Le 20/12/2012 18:34, Peter Dimov a écrit :
What is the recommended Boost.SIMD way to write a function like
void add_n( float const * s, float const * s2, float * d, size_t n ); // d[i] = s[i] + s2[i]
where none of s, s2, d are guaranteed to be aligned?
You should align them ;) More seriously, you can run a for using with pack and unaligned_load/store: void add_n( float const * s, float const * s2, float * d, size_t n ) { size_t c = pack<float>::static_size; size_t vn = v / c * c; size_t sn = v % c; for(std::size_t i=0, i<vn; i+= c, d+=c,s+=c,s2+=c) store(unaligned_load<pack<T>>(s) + unaligned_load<pack<T>>(s2), d ); for(std::size_t i=0, i<sn; i++,d++,s++,s2++) *d = *s + *s2; } This also takes the fact n can be not a multiple of pack cardinal into account. If pointer is aligned you can actually just use simd::input_iterator and feed this to std::transform. Maybe we should have a simd::unaligned_input_iterator and/or make simd::transform accept non aligned data. Note that on any pre-Nehalem CPU, the unaligned load will be horrendsously slow.