[ET Trac] [Einstein Toolkit] #2015: thorn Vectors does not provide a sum() reduction

[Einstein Toolkit]

#2015: thorn Vectors does not provide a sum() reduction
-------------------------+--------------------------------------------------
 Reporter:  rhaas        |       Owner:                     
     Type:  enhancement  |      Status:  new                
 Priority:  minor        |   Milestone:                     
Component:  Cactus       |     Version:  development version
 Keywords:  Vectors      |  
-------------------------+--------------------------------------------------
 It would be very useful for some applications (eg interpolation) if thorn
 Vectors provided a sum() function similar to the sum() member of
 vecmathlib

 https://bitbucket.org/eschnett/vecmathlib/src/477f9c85cf111e59a9042f230bb536d0765265fa/vec_avx_double4.h?at=master&fileviewer
 =file-view-default#vec_avx_double4.h-537
 {{{
 real_t sum() const {
   // return (*this)[0] + (*this)[1] + (*this)[2] + (*this)[3];
   // __m256d x = _mm256_hadd_pd(v, v);
   // __m128d xlo = _mm256_extractf128_pd(x, 0);
   // __m128d xhi = _mm256_extractf128_pd(x, 1);
   realvec_t x = *this;
   x = _mm256_hadd_pd(x.v, x.v);
   return x[0] + x[2];
 }
 }}}

 Most likely one can just copy and paste the code from vecmathlib.
 vecmathlib's license is not LGPL but permissive enough for inclusion and
 we can also ask Erik if one can use it and change the license of the
 affected code lines to LGPL in Cactus, the license is here:

 https://bitbucket.org/eschnett/vecmathlib/src/477f9c85cf111e59a9042f230bb536d0765265fa/LICENCE?at=master&fileviewer
 =file-view-default
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-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/2015>
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