# Command: testsuite::test_poisson_ps_intervals

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Name:

    testsuite::test_poisson_ps_intervals - checks coefficient of variation

Synopsis:

    (test_poisson_ps_intervals) run -> CV sufficiently close to 1

Description:

      The inter spike interval (ISI) distribution of a Poisson process is
      exponential. The coefficient of variation defined as the standard deviation
      of the intervals normalized by the mean interval is 1. The test checks whether
      the output of the poisson_generator_ps as recorded by the spike_detector is
      sufficiently close to 1. Without the property /precise_times the error is larger
      than 0.1 .

Remarks:

      An improved version of this test should check whether the observed deviation from
      unity is within the error bounds given by the number of spikes.
      Even a correct implementation generates with low probability spike trains  which
      do not pass the test. The seed set in the default configuration of NEST avoids
      this problem. Therefore, failure of this script indicates that the configuration
      is not portable.
      The test in r8067 worked even with ticket #157 unresolved. Only the presence of a
      neuron (see test_spike_transmission_ps_iaf) exhibited the problem. Prior to the
      fix of ticket #164 this test produced inconsistent results without specifying
      /local_num_threads 1 for the kernel.

Author:

    Diesmann, Plesser

FirstVersion:

    February 2008

Source:

    /opt/conda/conda-bld/nest_1512418852064/work/nest-2.12.0/testsuite/unittests/test_poisson_ps_intervals.sli

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