[Discuss-gnuradio] Assertion "imu >= 0" failed on random times

[Daniel Bartel]

Hello,

in the program I am currently working on, I sometimes get the following error 
messsage:

python: gri_mmse_fir_interpolator_cc.cc:66: gr_complex 
gri_mmse_fir_interpolator_cc::interpolate(const gr_complex*, float): 
Zusicherung »imu >= 0« nicht erfüllt.
Abgebrochen

It seems like the assertion "imu >= 0" failed.
The strange thing is, that the message behaves completely non-deterministic. 
e.g. When I start the program 4 times, on the first 3 runs I get the error 
message and suddenly at the 4th try, it runs without an error.

The assertion comes from the following method, which is located in the 
gri_mmse_fir_interpolator_cc.cc file.

gr_complex
gri_mmse_fir_interpolator_cc::interpolate (const gr_complex input[], float mu)
{
  int   imu = (int) rint (mu * NSTEPS);

  assert (imu >= 0);
  assert (imu <= NSTEPS);

  gr_complex r = filters[imu]->filter (input);
  return r;
}

Does anyone has an explanation for this behavior or for what "imu >= 0" stands 
for?

Thanks for your help,
Daniel