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improve approximate order on __getitem__ calls #34556

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mantepse opened this issue Sep 19, 2022 · 7 comments · Fixed by #35265
Closed

improve approximate order on __getitem__ calls #34556

mantepse opened this issue Sep 19, 2022 · 7 comments · Fixed by #35265
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c: combinatorics p: major / 3 t: enhancement
Milestone
sage-10.0

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@mantepse
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We improve the approximate order of a stream whenever Stream_inexact.__getitem__ is called.

This may slow down Stream_inexact.__getitem__ but should speed up other operations.

It must be checked carefully whether this is an overall improvement or not.

Depends on #34552

CC: @tscrim

Component: combinatorics

Keywords: LazyPowerSeries

Author: Martin Rubey

Branch/Commit: u/mantepse/improve_approximate_order_on___getitem___calls @ 5a2cb8b

Issue created by migration from https://trac.sagemath.org/ticket/34556
@mantepse mantepse added this to the sage-9.8 milestone Sep 19, 2022
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Branch: u/mantepse/improve_approximate_order_on___getitem___calls

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sagetrac-git mannequin commented Sep 19, 2022

Branch pushed to git repo; I updated commit sha1. New commits:

5a2cb8bimprove approximate order when getitem is called

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sagetrac-git mannequin commented Sep 19, 2022

Commit: 5a2cb8b

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Dependencies: #34552

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Changed keywords from none to LazyPowerSeries

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Author: Martin Rubey

@mkoeppe mkoeppe removed this from the sage-9.8 milestone Jan 29, 2023
This was referenced Mar 11, 2023
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@mantepse mantepse added this to the sage-10.0 milestone Mar 22, 2023
vbraun pushed a commit that referenced this issue Apr 1, 2023
gh-35265: Improve approximate order on getitem calls
3142be9 
    
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### 📚 Description

Calling `Stream_inexact.__getitem__(n)` for `n ==
self._approximate_order`, we can update `self._true_order` and
`self._approximate_order` as follows:

* if the result is non-zero, we now know that `n` is the true order
* otherwise, we know that `n+1` is a lower bound for the order.
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This fixes #35261, but it may not be the best fix, because it
potentially makes `__getitem__` slower.

Fixes #34556, which was the original issue.

### 📝 Checklist

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### ⌛ Dependencies
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URL: #35265
Reported by: Martin Rubey
Reviewer(s): Martin Rubey, Travis Scrimshaw
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Improve approximate order on getitem calls mantepse/sage
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