Outro
Steamed fish was amazing, matter of fact
Let me get some jerk chicken to go
Grabbed me one of them lemon pie theories
And let me get some of them benchmarks you theories too
The Look
At the time of writing, implementation-wise parallel download is ready:
Does this mean I’ve finished everything just-in-time? This sounds to good to be true! And how does it perform? Welp…
The Benchmark
Here comes the bad news: under a decent connection to the package index,
using fast-deps does not make pip faster. For best comparison,
I will time pip download on the following cases:
Average Distribution
For convenience purposes, let’s refer to the commands to be used as follows
pip--no-cache-dirdownload{requirement}# legacy-resolverpip--use-feature=2020-resolver\--no-cache-dirdownload{requirement}# 2020-resolverpip--use-feature=2020-resolver--use-feature=fast-deps\--no-cache-dirdownload{requirement}# fast-deps
In the first test, I used axuy and obtained the following results
| legacy-resolver | 2020-resolver | fast-deps |
|---|---|---|
| 7.709s | 7.888s | 10.993s |
| 7.068s | 7.127s | 11.103s |
| 8.556s | 6.972s | 10.496s |
Funny enough, running pip download with fast-deps in a directory
with downloaded files already took around 7-8 seconds. This is because
to lazily download a wheel, pip has to make many requests
which are apparently more expensive than actual data transmission on my network.
When is it useful then?
With unstable connection to PyPI (for some reason I am not confident enough to state), this is what I got
| 2020-resolver | fast-deps |
|---|---|
| 1m16.134s | 0m54.894s |
| 1m0.384s | 0m40.753s |
| 0m50.102s | 0m41.988s |
As the connection was unstable and that the majority of pip networking
is performed as CI/CD with large and stable bandwidth, I am unsure what this
result is supposed to tell (-;
Large Distribution
In this test, I used TensorFlow as the requirement and obtained the following figures:
| legacy-resolver | 2020-resolver | fast-deps |
|---|---|---|
| 0m52.135s | 0m58.809s | 1m5.649s |
| 0m50.641s | 1m14.896s | 1m28.168s |
| 0m49.691s | 1m5.633s | 1m22.131s |
Distribution with Conflicting Dependencies
Some requirement that will trigger a decent amount of backtracking by
the current implementation of the new resolver oslo-utils==1.4.0:
| 2020-resolver | fast-deps |
|---|---|
| 14.497s | 24.010s |
| 17.680s | 28.884s |
| 16.541s | 26.333s |
What Now?
I don’t know, to be honest. At this point I’m feeling I’ve failed my own
(and that of other stakeholders of pip) expectation and wasted the time
and effort of pip’s maintainers reviewing dozens of PRs I’ve made
in the last three months.
On the bright side, this has been an opportunity for me to explore the codebase
of package manager and discovered various edge cases where the new resolver
has yet to cover (e.g. I’ve just noticed that pip download would save
to-be-discarded distributions, I’ll file an issue on that soon). Plus I got
to know many new and cool people and idea, which make me a more helpful
individual to work on Python packaging in the future, I hope.
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