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<p>Good morning,</p>
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<p>I have made some thoughts about the problems with SPH and MPI.</p>
<p>I found a paper by Valdez-Balderas et al (2012) (http://adsabs.harvard.edu/abs/2012arXiv1210.1017V), which could help to solve some of the problems.</p>
<p>They suggest a particle halo on each processor unit, in which the neighbour particle of the adjacent processors are saved. This should be synchronized in each timestep.</p>
<p>One problem of this method is SPH have to use fixed smoothlength, otherwise the volume of the halo can't be set. The variability of the smoothlength is required to have an adaptive refinement in the SPH-algorithm. I would suggest to use semi-fixed smoothlength, which are smaller in higher refindement levels. This could reduce the disadvantages of the fixed smoothlength.</p>
<p>What is your opinion this? </p>
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<p>Now I try to test how good SPH-approximations for the hydrodynamic grid variables in the Tmunu base are under the condition of such "adaptive-fixed" smoothlength. I have an other method in mind, but this would need more temporary memory.</p>
<p>Best regards,</p>
<p>Stefan Ruehe</p>
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