[eigen] A vector indexed by another vector

[Matthieu Brucher <matthieu.brucher@xxxxxxxxx>]

Hi,

I'd like to replace some of my code that consits of a indexed for loop by a pure Eigen statement. 

In fact, I have several of these loops, but the most simple one is the following:

  Vector vector;

  vector.resize(size);

  for(long j = 0; j < size; ++j)

  {

    long i = offset[j];

    float tmp = t02 + h2[i] * val[0];

    vector[j] =  tmp > 0.0f ? std::sqrt(tmp) + tsdiff[i] : -1000.f;

  }

The issue is that h2 is not accessed in order, but with values from the offset vector. Is there a way to efficiently write this kind of loop with Eigen?

Cheers,

Matthieu

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