Element-wise vector-vector multiplication in BLAS?

Question

Is there a means to do element-wise vector-vector multiplication with BLAS, GSL or any other high performance library ?

Answer 1

There is always std::valarray¹ which defines elementwise operations that are frequently (Intel C++ /Quse-intel-optimized-headers, G++) compiled into SIMD instructions if the target supports them.

• http://software.intel.com/sites/products/documentation/hpc/composerxe/en-us/cpp/mac/cref_cls/common/cppref_valarray_intro.htm

Both these compilers will also do auto-vectorization

• http://software.intel.com/en-us/articles/getting-code-ready-for-parallel-execution-with-intel-parallel-composer/
• http://gcc.gnu.org/projects/tree-ssa/vectorization.html

In that case you can just write

#define N 10000 

float a[N], b[N], c[N]; 

void f1() { 
  for (int i = 1; i < N; i++) 
  c[i] = a[i] + b[i]; 
} 

and see it compile into vectorized code (using SSE4 e.g.)

¹ Yes they are archaic and often thought of as obsolete, but in practice they are both standard and fit the task very well.