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Error running usearch61

# run otu picking with usearch61 -i $PWD/SEQ/seqs.fna -o $PWD/OTU/ -r $REFSEQS -s 0.1 -m usearch61 -p $PWD/otu_settings.txt

Error running usearch61. Possible causes are unsupported version (current supported version is usearch v6.1.544) is installed or improperly formatted input file was provided

# check log file
cat OTU/step1_otus/abundance_sorted.log
usearch_i86linux32 v6.1.544, 4.0Gb RAM (8.1Gb total), 4 cores
---Fatal error---
Out of memory, mymalloc(34603016), curr 4.27e+09 bytes

"Out of memory": number of sequences exceeds the 4GB memory limit of the 32 bit version of usearch61.

Work around:
Run without option "pick_otus:enable_rev_strand_match True" to half the memory usage. 

upgrade to a 64 bit version of usearch61 (not free)

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