README.md

Downsample signature --scaled values

Usage:

./sourmash compute --scaled 5000 data/GCF_000005845.2_ASM584v2_genomic.fna.gz -f

python e7d910326792554e1fbf826fe12da83f/subscaled.py GCF_000005845.2_ASM584v2_genomic.fna.gz.sig foo.sig 10000

and now foo.sig will contain the newly subscaled signature.

subscaled.py

#! /usr/bin/env python3
import sys
import screed
import sourmash_lib.signature
import copy

in_fp = open(sys.argv[1])
sigs = list(sourmash_lib.signature.load_signatures(in_fp))
new_scaled = float(sys.argv[3])
max_hash = 2**64 / float(new_scaled)

# for each signature, extract state, change max_hash, and reinstantiate.
for sig in sigs:
    print('processing {}'.format(sig.name()))
    state = sig.estimator.__getstate__()
    state = list(state)
    
    assert max_hash < state[6], \
      "'scaled' can only increase from original sigs."
    state[6] = max_hash
    sig.estimator.__setstate__(state)

# save!
out_fp = open(sys.argv[2], 'wt')
print(sourmash_lib.signature.save_signatures(sigs), file=out_fp)