example using simd::abs

Author: kevinushey

examples/boost-simd-abssum.cpp

@@ -0,0 +1,49 @@
+// [[Rcpp::depends(RcppParallel)]]
+#include <RcppParallel.h>
+#include <Rcpp.h>
+using namespace Rcpp;
+
+#include <boost/simd/sdk/simd/pack.hpp>
+#include <boost/simd/memory/allocator.hpp>
+#include <boost/simd/include/functions/sum.hpp>
+#include <boost/simd/include/functions/load.hpp>
+#include <boost/simd/include/functions/plus.hpp>
+#include <boost/simd/include/functions/multiplies.hpp>
+#include <boost/simd/include/functions/abs.hpp>
+
+// [[Rcpp::export]]
+double simd_abssum(NumericVector x)
+{
+   using boost::simd::pack;
+   using boost::simd::load;
+   using boost::simd::aligned_load;
+   
+   typedef std::vector< double, boost::simd::allocator<double> > vector_type;
+   typedef pack<double> packed_type;
+   
+   vector_type data(x.begin(), x.end());
+   
+   packed_type packed;
+   double* it = &data[0];
+   double* end = &data[0] + data.size();
+   
+   while (it != end)
+   {
+      packed_type loaded = load<packed_type>(it);
+      packed = packed + boost::simd::abs(loaded);
+      it += packed_type::static_size;
+   }
+   
+   return sum(packed);
+}
+
+/*** R
+n <- 1024 * 1000
+x <- rnorm(n)
+
+library(microbenchmark)
+microbenchmark(
+   R = sum(abs(x)),
+   simd = simd_abssum(x)
+)
+*/

examples/boost-simd-dot.cpp

@@ -24,8 +24,8 @@ Value simd_dot(Value* first1, Value* last1, Value* first2)
    while (first1 != last1)
    {
       // Load current values from the datasets
-      pack<Value> x1(first1);
-      pack<Value> x2(first2);
+      pack<Value> x1 = boost::simd::aligned_load<Value>(first1);
+      pack<Value> x2 = boost::simd::aligned_load<Value>(first2);
 
       // Computation
       tmp = tmp + x1 * x2;