BUG: Use float64 for row counter in rank()
State: closed

- [X] closes #18271
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

As reported in #18271, for a large `Series` `s` of `float`s, `Series.rank(pct=True).max()` may not be `<=1` as expected.

This is due to the use of a `float` for the row counter. This updates the counter to use a `float64`.


Labels:
name: Numeric Operations
description: Arithmetic, Comparison, and Logical operations

Comments:
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=h1) Report
> Merging [#18274](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/69472f9ae9c645a0a5932c7c65b6efbdf66fbb5f?src=pr&el=desc) will **decrease** coverage by `0.02%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18274/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18274      +/-   ##
==========================================
- Coverage    91.4%   91.38%   -0.03%     
==========================================
  Files         164      164              
  Lines       49878    49878              
==========================================
- Hits        45590    45580      -10     
- Misses       4288     4298      +10
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.18% <ø> (-0.01%)` | :arrow_down: |
| #single | `39.41% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.38% <0%> (-0.1%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=footer). Last update [69472f9...bfee0fe](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=h1) Report
> Merging [#18274](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ef4e30b85fa3058f0127a969ae7576f0ef3f7454?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18274/graphs/tree.svg?height=150&token=eZ4WkYLtcO&width=650&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #18274      +/-   ##
==========================================
+ Coverage   91.37%   91.38%   +<.01%     
==========================================
  Files         164      164              
  Lines       49880    49880              
==========================================
+ Hits        45580    45583       +3     
+ Misses       4300     4297       -3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.19% <ø> (+0.02%)` | :arrow_up: |
| #single | `39.42% <ø> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.8% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `95% <0%> (ø)` | :arrow_up: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.25% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=footer). Last update [ef4e30b...d509360](https://codecov.io/gh/pandas-dev/pandas/pull/18274?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).

When I rerun the same code from #18271, I get the same result in `Rank_Pct` and `Rank_Pct_Manual`:

```
                abc          Rank      Rank_Pct  Rank_Pct_Manual
count  2.000000e+07  2.000000e+07  2.000000e+07     2.000000e+07
mean   4.999223e-01  1.000000e+07  5.000000e-01     5.000000e-01
std    2.886891e-01  5.773503e+06  2.886751e-01     2.886751e-01
min    1.036192e-08  1.000000e+00  5.000000e-08     5.000000e-08
25%    2.498756e-01  5.000001e+06  2.500000e-01     2.500000e-01
50%    4.999781e-01  1.000000e+07  5.000000e-01     5.000000e-01
75%    7.499111e-01  1.500000e+07  7.500000e-01     7.500000e-01
max    1.000000e+00  2.000000e+07  1.000000e+00     1.000000e+00
```

tests
pls rebase and update to comments
closing as stale. if you want to continue working, pls ping.