[MRG] fix scaled=1 gather bug

[ctb]

Creates a test for & and fixes a bug noted in #1421 (comment) - the default "unset" value used in the #1613 code was set to a valid scaled value, and we never tested it! Oops!

[codecov]

Codecov Report

Merging #1670 (d101fb3) into latest (02f2128) will increase coverage by 7.40%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           latest    #1670      +/-   ##
==========================================
+ Coverage   82.35%   89.76%   +7.40%     
==========================================
  Files         113       86      -27     
  Lines       11772     8058    -3714     
  Branches     1490     1490              
==========================================
- Hits         9695     7233    -2462     
+ Misses       1818      566    -1252     
  Partials      259      259              

Flag	Coverage Δ
python	89.76% <100.00%> (ø)
rust	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/sourmash/search.py	96.91% <100.00%> (ø)
src/core/src/signature.rs
src/core/src/index/linear.rs
src/core/src/ffi/cmd/compute.rs
src/core/src/sketch/nodegraph.rs
src/core/src/ffi/mod.rs
src/core/src/index/sbt/mod.rs
src/core/src/index/mod.rs
src/core/src/ffi/nodegraph.rs
src/core/src/ffi/hyperloglog.rs
... and 18 more

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[ctb]

Ready for review & merge @sourmash-bio/devs

[taylorreiter]

the test LGTM, but I don't understand the difference between

self.cmp_scaled = 1

and

self.cmp_scaled = 0     # initialize with something very low!

[ctb]

the test LGTM, but I don't understand the difference between

self.cmp_scaled = 1

and

self.cmp_scaled = 0     # initialize with something very low!

The issue is this line

sourmash/src/sourmash/search.py

Line 320 in d101fb3

if self.cmp_scaled != max_scaled:

, where we have an if statement that updates the object properties if and only if scaled has increased. I used this to initialize the object properties the first time through by setting the initial cmp_scaled to a value of 1, which means (before this change) it would only initialize the object properties for a scaled > 1.

It's not great code, to be fair. But rather than making bigger changes I decided to just patch it and test it :)

[taylorreiter]

where we have an if statement that updates the object properties if and only if scaled has increased. I used this to initialize the object properties the first time through by setting the initial cmp_scaled to a value of 1, which means (before this change) it would only initialize the object properties for a scaled > 1

Ah this makes sense, thank you for the explanation!

[taylorreiter]

LGTM!

[ctb]

thanks!