feat(gsoc): Negative Weights #1820

Saptaparna · 2026-01-30T01:24:51Z

PR for two projects on negative weight mitigation.

netlify · 2026-01-30T01:24:57Z

✅ Deploy Preview for earnest-hotteok-b1e1bf ready!

Name	Link
🔨 Latest commit	`92e0a77`
🔍 Latest deploy log	https://app.netlify.com/projects/earnest-hotteok-b1e1bf/deploys/698b367db26ce400082dbcfb
😎 Deploy Preview	https://deploy-preview-1820--earnest-hotteok-b1e1bf.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

To edit notification comments on pull requests, go to your Netlify project configuration.

Saptaparna · 2026-01-30T01:25:53Z

@graeme-a-stewart @eduardo-rodrigues Tagging admins

Saptaparna · 2026-01-30T01:31:11Z

@simonspa

Saptaparna · 2026-01-30T01:54:26Z

label:"GSoC"

maszyman

Thanks for the proposals.

Please have a look at my comments inline.

Also, please consider adding AI policy, for example as suggested in #1804 (comment)

maszyman · 2026-01-30T09:34:15Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+-
+project: HSF
+title: HSF
+layout: default
+logo: hsf_logo_angled.png
+description: |
+  The HEP Software Foundation encourages cooperation and common
+  development of software in High Energy Physics. The HSF hosts
+  a number of software projects where developers are working to
+  solve current problems in particle physics.
+---
+
+{% include gsoc_project.ext %}
+


This does not seem to be needed. Please have a loot at template in e.g. #1804

maszyman · 2026-01-30T09:36:32Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+-
+title: Negative weight mitigation with cell resampling in ATLAS workflows
+layout: gsoc_proposal
+project: Negative weight, ATLAS event generator workflows


This should correspond to the project that needs to be defined in _gsocproject/2026/. We already have there ATLAS is that what this proposal targets.

Suggested change

project: Negative weight, ATLAS event generator workflows

project: ATLAS

maszyman · 2026-01-30T09:38:02Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+layout: gsoc_proposal
+project: Negative weight, ATLAS event generator workflows
+year: 2026
+organization: Southern Methodist University


This name should correspond to the definition in _gsocorgs/2026. Please check the examples, but you may need to create smu.md in there.

Suggested change

organization: Southern Methodist University

organization: SMU

maszyman · 2026-01-30T09:39:09Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+
+Negatively weighted events arise as a result of subtraction schemes in next-to-leading (or higher) order event generators. The fraction of negatively weighted events vary as a function of phase space requirements that are imposed in experimental analyses making it imperative to store these events for time consuming downstream processing like detector simulation. They are a severe source of inefficiency in event generator workflows, requiring large datasets to mitigate statistical dilution caused by negatively weighted events.  
+
+A method to redistribute negatively weighted events was proposed in arXiv:2109.07851 and subsequently in  arXiv:2303.15246. We plan to use this method for ATLAS event generator workflows. The method has been previously implemented in CMS for small-scale tests. In this project, we will extend the scope of previous explorations in both ATLAS and CMS by identifying computationally intensive workflows and running validation tests that are designed to ensure that distributions of physical observables are not sculpted as a result of the removal of negatively weighted events.


Please make those arXiv references the clickable links.

maszyman · 2026-01-30T09:39:55Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+ * Design an event generator workflow and validation suite that tests the cell resampling method for negative weight removal
+
+## Requirements
+ * Familiarity with python and C++  


Suggested change

* Familiarity with python and C++

* Familiarity with Python and C++

maszyman · 2026-01-30T09:41:44Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+  * [Saptaparna Bhattacharya](mailto:saptaparna.bhattacharya@cern.ch)
+
+## Links
+  * [Cell resampling](https://cres.hepforge.org/)


This looks to be a Rust project. Would it make sense to add it in requirements?

maszyman · 2026-01-30T09:42:36Z

_gsocproposals/2026/proposal_NegativeWeightsMCFM.md

@@ -0,0 +1,51 @@
+-
+project: HSF


Same editorial comments as for the previous proposal.

maszyman · 2026-01-30T09:45:40Z

_gsocproposals/2026/proposal_NegativeWeightsMCFM.md

+
+## Expected results
+Release a modified version of MCFM that successfully incorporates the negative weight mitigation strategy, demonstrating reduced statistical dilution.
+


You are missing Mentors section (should be done via project_mentors in the metadata at the top).

If you are the only mentor also for this project, please consider adding a co-mentor as Google suggests that mentors should mentor 1 contributor project, and there should be preferably 2 mentors per project.

maszyman · 2026-02-02T13:14:15Z

@Saptaparna could you please update the PR following the comments?

maszyman · 2026-02-04T09:46:45Z

@Saptaparna just a kind reminder to update this PR.

Saptaparna · 2026-02-09T06:05:45Z

@maszyman done!

maszyman

Thanks for the updates. There are still a couple changes needed to properly render the project.

maszyman · 2026-02-09T08:35:36Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+layout: gsoc_proposal
+project: Negative weight, ATLAS event generator workflows
+year: 2026
+organization: Southern Methodist University


Suggested change

organization: Southern Methodist University

organization: SMU

maszyman · 2026-02-09T08:35:56Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+-
+title: Negative weight mitigation with cell resampling in ATLAS workflows
+layout: gsoc_proposal
+project: Negative weight, ATLAS event generator workflows


Suggested change

project: Negative weight, ATLAS event generator workflows

project: ATLAS

maszyman · 2026-02-09T08:36:55Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

@@ -0,0 +1,40 @@
+-


Suggested change

-

---

maszyman · 2026-02-09T08:39:30Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+difficulty: medium
+duration: 175
+mentor_avail: June-October
+project_mentors: Saptaparna Bhattacharya (saptaparnab@smu.edu) and authors of the "cell-resampling" team (Jeppe Andersen(mailto:eppe.andersen@durham.ac.uk) and Andreas Maier(mailto:andreas.martin.maier@desy.de))


Suggested change

project_mentors: Saptaparna Bhattacharya (saptaparnab@smu.edu) and authors of the "cell-resampling" team (Jeppe Andersen(mailto:eppe.andersen@durham.ac.uk) and Andreas Maier(mailto:andreas.martin.maier@desy.de))

project_mentors:

- email: saptaparnab@smu.edu

first_name: Saptaparna

last_name: Bhattacharya

organization: SMU

is_preferred_contact: yes

and similarly for the co-mentors

maszyman · 2026-02-09T08:40:09Z

_gsocproposals/2026/proposal_NegativeWeightsATLAS.md

+## Mentors
+  * [Saptaparna Bhattacharya](mailto:saptaparna.bhattacharya@cern.ch) and authors of the "cell-resampling" team (Jeppe Andersen(mailto:eppe.andersen@durham.ac.uk) and Andreas Maier(mailto:andreas.martin.maier@desy.de))


Suggested change

## Mentors

* [Saptaparna Bhattacharya](mailto:saptaparna.bhattacharya@cern.ch) and authors of the "cell-resampling" team (Jeppe Andersen(mailto:eppe.andersen@durham.ac.uk) and Andreas Maier(mailto:andreas.martin.maier@desy.de))

This is handled by project_mentors metadata

maszyman · 2026-02-09T08:41:14Z

_gsocproposals/2026/proposal_NegativeWeightsMCFM.md

+-
+title: Negative weight mitigation with cell resampling and tests with MCFM
+layout: gsoc_proposal
+project: Negative weight, MCFM


Suggested change

project: Negative weight, MCFM

project: MCFM

and please add MCFM.md to _gsocprojects/2026/

maszyman · 2026-02-09T08:41:27Z

_gsocproposals/2026/proposal_NegativeWeightsMCFM.md

+difficulty: medium
+duration: 175
+mentor_avail: June-October
+project_mentors: Tobias Neumann (tneumann@mail.smu.edu), Saptaparna Bhattacharya (saptaparnab@smu.edu) 


same comment as previous proposal

Saptaparna · 2026-02-09T14:31:16Z

AI policy is now there too.

Updated organization details and mentor organization.

maszyman · 2026-02-10T13:47:40Z

Thanks @Saptaparna , I've made few adjustments, but I think now it's ready.

Negative Weights

c8e5d74

Saptaparna changed the title ~~Negative Weights~~ feat(gsoc): Negative Weights Jan 30, 2026

Saptaparna marked this pull request as draft January 30, 2026 01:50

Saptaparna changed the title ~~feat(gsoc): Negative Weights~~ feat(gsoc): Negative Weights label:"GSoC" Jan 30, 2026

Saptaparna changed the title ~~feat(gsoc): Negative Weights label:"GSoC"~~ feat(gsoc): Negative Weights Jan 30, 2026

Saptaparna marked this pull request as ready for review January 30, 2026 01:54

maszyman added the GSoC Related to Google Summer of Code activity label Jan 30, 2026

maszyman requested a review from a team January 30, 2026 09:24

maszyman requested changes Jan 30, 2026

View reviewed changes

Update

6085714

Saptaparna added 3 commits February 8, 2026 23:47

Addressing comments

5ebce2e

Addressing comments

565140c

Addressing comments

a75632f

maszyman requested changes Feb 9, 2026

View reviewed changes

Addressing comments

89af048

Saptaparna and others added 6 commits February 9, 2026 23:46

Addressing comments

897f869

Addressing comments

e787539

Update title for Negative Weights MCFM proposal

603e238

Update title for NegativeWeightsATLAS proposal

d3c45af

Update organization field for project mentors

1bd1c5f

Modify organization and mentor details in proposal

92e0a77

Updated organization details and mentor organization.

maszyman approved these changes Feb 10, 2026

View reviewed changes

maszyman merged commit 807d277 into HSF:main Feb 10, 2026
5 checks passed

	project: Negative weight, ATLAS event generator workflows
	project: ATLAS

	organization: Southern Methodist University
	organization: SMU


		Negatively weighted events arise as a result of subtraction schemes in next-to-leading (or higher) order event generators. The fraction of negatively weighted events vary as a function of phase space requirements that are imposed in experimental analyses making it imperative to store these events for time consuming downstream processing like detector simulation. They are a severe source of inefficiency in event generator workflows, requiring large datasets to mitigate statistical dilution caused by negatively weighted events.

		A method to redistribute negatively weighted events was proposed in arXiv:2109.07851 and subsequently in arXiv:2303.15246. We plan to use this method for ATLAS event generator workflows. The method has been previously implemented in CMS for small-scale tests. In this project, we will extend the scope of previous explorations in both ATLAS and CMS by identifying computationally intensive workflows and running validation tests that are designed to ensure that distributions of physical observables are not sculpted as a result of the removal of negatively weighted events.

	* Familiarity with python and C++
	* Familiarity with Python and C++


		## Expected results
		Release a modified version of MCFM that successfully incorporates the negative weight mitigation strategy, demonstrating reduced statistical dilution.

-project_mentors: Saptaparna Bhattacharya (saptaparnab@smu.edu) and authors of the "cell-resampling" team (Jeppe Andersen(mailto:eppe.andersen@durham.ac.uk) and Andreas Maier(mailto:andreas.martin.maier@desy.de))
+project_mentors:
+  - email: saptaparnab@smu.edu
+    first_name: Saptaparna
+    last_name: Bhattacharya
+    organization: SMU
+    is_preferred_contact: yes

		## Mentors
		* [Saptaparna Bhattacharya](mailto:saptaparna.bhattacharya@cern.ch) and authors of the "cell-resampling" team (Jeppe Andersen(mailto:eppe.andersen@durham.ac.uk) and Andreas Maier(mailto:andreas.martin.maier@desy.de))

feat(gsoc): Negative Weights #1820

feat(gsoc): Negative Weights #1820

Conversation

Saptaparna commented Jan 30, 2026

Uh oh!

netlify bot commented Jan 30, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

✅ Deploy Preview for earnest-hotteok-b1e1bf ready!

Uh oh!

Saptaparna commented Jan 30, 2026

Uh oh!

Saptaparna commented Jan 30, 2026

Uh oh!

Saptaparna commented Jan 30, 2026

Uh oh!

maszyman left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

maszyman Jan 30, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

maszyman commented Feb 2, 2026

Uh oh!

maszyman commented Feb 4, 2026

Uh oh!

Saptaparna commented Feb 9, 2026

Uh oh!

maszyman left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Saptaparna commented Feb 9, 2026

Uh oh!

maszyman commented Feb 10, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

netlify bot commented Jan 30, 2026 •

edited

Loading

maszyman Jan 30, 2026 •

edited

Loading