Grouped calculations of list columns are very slow
Nobody has claimed this yet.
Assessment
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Newbie friendliness
- 35/100
- Issue type
- Bug
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- r
- Domain
- data, performance
Research direction
Start by reproducing the two grouped calculations shown in the issue and compare their timings. Trace the grouped list-column calculation path to find why the second call is disproportionately slower; done means its runtime is no longer about three times the first call while preserving the demonstrated results.
Written by the indexing model from the issue text.
Description
Calculations get very slow when we create list columns. Consider these two calls:
dt <- data.table::data.table(x = sample(10000, 10000000, TRUE), y = sample(10000, 10000000, TRUE), z = sample(10000, 10000000, TRUE))
system.time(dt[, .I, by = c("x", "y")])
system.time(dt[, .(.(.I)), by = c("x", "y")])
The second one should take about 3 times as long as the first one, which is not really reasonable (especially since the first call is not particularly fast, compared to more typical calculations).
- Dominant language
- R
- Stars
- 3.9k
- Forks
- 1.1k
- Avg merge
- 14h 4m
- Merged PRs (30d)
- 4
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
More from Rdatatable/data.table
-
as.data.table() recurses without end on a survival::Surv object (or any data.frame carrying one) Open
Difficulty 2/5 1-3 hours Newbie friendliness 88/100
Rdatatable/data.table#7887 ·
-
consistency tests
Difficulty 2/5 1-3 hours Newbie friendliness 68/100
Rdatatable/data.table#7853 · 3 comments ·
-
internals
Difficulty 2/5 1-3 hours Newbie friendliness 65/100
Rdatatable/data.table#6938 · 1 comment ·
-
encoding fread
Difficulty 2/5 1-3 hours Newbie friendliness 65/100
Rdatatable/data.table#5179 · 8 comments ·
-
documentation programming
Difficulty 2/5 1-3 hours Newbie friendliness 68/100
Rdatatable/data.table#3199 · 3 comments ·
All issues in Rdatatable/data.table
Similar issues
-
Difficulty 2/5 1-3 hours Newbie friendliness 82/100
r-lib/pkgdepends#485 · 3 comments ·
-
Difficulty 1/5 Under an hour Newbie friendliness 92/100
-
beginners blocker
Difficulty 2/5 1-3 hours Newbie friendliness 78/100
-
enviPathR OpenBuild Error Build OK Build Warning policies-accepted pre-review precheck-passed
Difficulty 1/5 Under an hour Newbie friendliness 84/100
Bioconductor/BiocContributions#207 · 6 comments ·
-
Difficulty 2/5 1-3 hours Newbie friendliness 74/100
datacarpentry/semester-biology#1255 ·