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Unable to perform downsampling: segfault #278

@raghuttamh

Description

@raghuttamh

Issue Summary
I have a minute long filterbank file sampled at 64us with 4096 frequency channels. Now, I am trying to python/dedisp_with_aa.py with a custom DDPlan and this throws segmentation fault whenever I try to set downsample >1. I have the latest master branch installed and have pasted the ddplan in the section below

Steps to Reproduce
The dedispersion plan is

dDMs      = [0.32] 
dsubDMs   = [1] 
downsamps = [4] 
subcalls  = [2048] 
startDMs  = [0.0] 
dmspercall = 1

If I set the downsamps to [1], everything runs smooth.

Expected Outcome
Pipeline runs and provides me a output buffer of DM-time

Actual Outcome

Memory allocation for the DDTR
Number of time samples: 232064;
maxshift: 9184
Number of time samples + maxshift: 241248;
Number of channels: 4096
Maximum number of DM-trials: 2048;
Available memory: 33749729280 bytes = 32186.250 MB;
DDTR input size: 1976303616 bytes = 1884.750 MB;
DDTR output size:  3952607232 bytes = 3769.500 MB;
Total memory required: 5928910848 bytes = 5654.250 MB;
Apr 16 10:34:14 2025 - NOTICE   Pipeline running over next chunk.
NOTICE: Pipeline start/resume run_pipeline_generic.

NOTICE: t_processed:    232064, 0

NOTICE: 0.000000        655.359985      0.320000        2048

Amount of telescope time processed: 0.000000
Segmentation fault (core dumped)

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