📄 Technical problem specification (PDF)
Version: 1.0 (Official) Issue date: June 8, 2026 Issuing authority: Board of Directors of the Mexican Society for Operations Research (SMIO) Diamond Sponsor: Hexaly
This is a courtesy English translation. The Spanish version is authoritative; in case of any discrepancy between the two, the Spanish version prevails (§14.2).
These rules govern participation in the SMIO–Hexaly Location Routing Challenge 2026 (hereinafter, "the Challenge"). By registering, participants and their teams fully accept the provisions set forth herein.
The Challenge is organized by the Mexican Society for Operations Research (SMIO) with Hexaly as Diamond Sponsor. It is associated with the XIV SMIO Congress (XIV CSMIO), to be held October 7–9, 2026, at the Universidad de Monterrey, Nuevo León, Mexico.
The Challenge invites the Operations Research community to solve a set of 30 instances of the Capacitated Location Routing Problem (CLRP), using any method of their choice. The best solutions found by participating teams are integrated into a permanent reference library.
These rules are accompanied by the following documents, which form an integral part of the regulations by reference:
In case of any contradiction between documents, these rules prevail.
For the purposes of these rules:
Each team must satisfy, at the time of registration, two membership requirements:
Information about SMIO membership categories and renewal is available at smio.org, specifically at SMIO Membership.
Within the framework of the alliance with the Latin-Iberoamerican Operations Research Association (ALIO), a current membership in a sister national society of the ALIO community (Latin American countries, Spain, and Portugal) is by itself a valid membership for the purposes of the team requirement in §3.1. The full list of ALIO member countries can be found at: ALIO
The following may not participate in the Challenge:
Teams of up to three people pursuing an undergraduate or higher-level technical degree, plus one guide. The guide may be any person who is not an undergraduate student at the time of registration (for example, graduate students, faculty, or industry professionals).
Undergraduate-student status is determined on the team's registration date. A person who graduates during the competition window does not lose eligibility retroactively. Likewise, a person whose most recent academic term of an undergraduate or higher-level technical program was the January–June/July 2026 semester is considered an undergraduate student, even if they have already graduated by the registration or competition date.
Teams of up to three people, with no profile restrictions. Students, academic staff, and industry members may participate.
Each person may belong to only one team. Membership is verified at the time of registration.
A team's roster becomes fixed when formal team registration closes in July 2026. No subsequent additions are allowed. The withdrawal of a member during the competition window, for justified cause, must be reported to SMIO; the team continues with the reduced roster and there is no retroactive score adjustment.
Registration is carried out through self-declaration on the Platform. Each member declares, under penalty of perjury:
SMIO reviews each team registration and approves it before enabling solution submission. In case of rejection, the reason is notified and the team may correct and resubmit the registration.
Each team must provide at the time of registration:
The problem formulation, parameters, objective function, and constraints are detailed in the complementary technical specification. In summary, the problem consists of simultaneously deciding: which depots to open, how to assign customers to open depots, and how to design the vehicle routes, minimizing the total cost (depot opening + fixed cost per route + total distance traveled) subject to depot capacity, vehicle capacity, and maximum-number-of-vehicles-per-depot constraints.
30 official instances will be published at the start of the competition window, distributed across small, medium, and large scales, covering between 200 and 3,000 customers and between 10 and 50 depots. The small- and medium-scale instances use Euclidean distances on synthetic coordinates; the large-scale ones use real road-network distances from the Monterrey Metropolitan Area, which may be asymmetric.
The official instances will not be published before the start of the competition window. Prior to the start, SMIO will publish an open-source instance generator (June 2026) so that teams can develop and test their methods on analogous synthetic instances.
Before the start of the competition window, Hexaly will run its Hexaly Optimizer solver on the 30 official instances to produce a reference solution for each. These solutions:
SMIO provides an open-source official verifier that evaluates the feasibility and cost of any solution. Teams may use it locally to validate their own solutions before submitting them.
The official verifier running on the Platform is the sole arbiter of feasibility and cost. Any discrepancy between local implementations and the official verifier is resolved in favor of the official one.
All submissions must be made through the official Platform of the Challenge. Submissions by email, courier, or any other channel are not accepted.
Solutions must comply with the format specified in the complementary technical specification. Any solution that cannot be processed by the verifier due to format errors will be rejected with a diagnostic, and the submission will not affect lead time.
The official timestamp of a submission is the time the file is received by the Platform, recorded in UTC. This timestamp is used for the lead-time calculation. Subsequent processing times (verification, database writing) do not affect the official timestamp.
All times in the public Platform interface are shown in the America/Monterrey (UTC−6, no daylight saving) time zone, with the UTC timestamp available on hover.
Each submission is processed by the official verifier. The result may be:
In the event that a feasible submission has a cost exactly equal to that of the current BKS, the incumbent BKS is retained. The team that first established the BKS keeps the lead. The numerical tolerance for determining equality is the same as that applied by the verifier: 10^{-4} absolute.
To preserve Platform stability and avoid accidental mass submissions:
Infeasible submissions do not count toward these limits.
The chronological evolution of the BKS per instance is published in real time during the competition window. For each instance, the Platform publicly displays:
The solution files themselves (the .sol files) and the metadata referred to in §7.8 (computation time, environment description) are not published during the window: they are added to the permanent reference library at the close, in accordance with section 13.
When a submission results in a new BKS for an instance, the Platform requests from the team, through a prompt after verification, additional information about that specific submission:
This information may be completed at any time before the close of the competition window. The Platform sends an email reminder 24 hours before the close to teams with pending information. The collected information is included in the reference library alongside the corresponding solution. Its omission does not affect the team's score, but the corresponding entry in the reference library is marked as "incomplete metadata."
For each instance \ell and each team t, we define:
The calculation is performed with second-level precision and expressed in decimal days (for example, 36 hours equals 1.5 days). The windows are sliding: a team's timer starts at the exact instant of the official timestamp of the submission that establishes its BKS, and stops at the exact instant another team displaces it or the competition window closes.
No lead time accrues on an instance before some team has established the first feasible BKS for that instance.
For each instance \ell and each team t, we define:
The total score of team t is:
where B is the final-BKS bonus, expressed in equivalent days. The Board of Directors selects the value of B with the criterion of balancing the incentive for sustained leadership with the incentive for a strong finish.
Value of B for the 2026 Challenge: B = 3 days.
In each Category (Undergraduate and Open), one winning team is declared: the one with the highest total score S_t within its Category. In the event of an exact tie in total score, the Board of Directors will apply the following tie-breaking criteria, in order:
During the competition window, the Platform maintains four public views:
At the close of the window, the solution files of each historical BKS (the .sol files themselves) and the §7.8 metadata are additionally published, integrated into the permanent reference library.
Each team must submit a Method Description in PDF format through the Platform. It must be a brief and concise description of the method used; no fixed maximum length is required.
The Method Description is submitted when formalizing the team at registration. The Platform does not allow completing a team's registration without prior upload of the file.
The Method Description must include, at a minimum, the sections of the official template (Appendix A):
The Method Description may be submitted in Spanish or in English, at the team's choice.
A team that does not submit a Method Description may not participate.
The Board of Directors reviews each Method Description before the awarding of prizes. In the event that the document is excessively long, omits required sections, or does not allow the method used to be clearly identified, the Board may request a revised version.
Each team works independently. The exchange between teams of solutions, source code, solver configurations, or intermediate results during the competition window is not allowed.
All submitted work must be produced exclusively by the team's registered members (including the guide in the Undergraduate Track), with the support of the computing tools (§10.3) and artificial intelligence tools (§10.4) permitted by these rules. Receiving assistance, information, code, or solutions from people outside the registered roster is not allowed, whether from other teams or from third parties. Any external contribution of this nature constitutes a de facto extension of the roster and violates section 4.
The use of any computing tool or solver is allowed, including:
Free academic licenses of Hexaly Optimizer are available to all academic participants registered in the Challenge, regardless of whether they use Hexaly to compete. The application procedure is indicated on the Hexaly platform.
The use of artificial intelligence tools is permitted, including programming assistants based on large language models (for example, Claude, Copilot, ChatGPT, Cursor).
There are no hardware restrictions. Teams may use any computational resource at their disposal: personal computers, institutional clusters, cloud computing services, specialized hardware (GPU, TPU).
For the purposes of the reference library, each team must self-report in its Method Description the hardware configuration used and the approximate real wall-clock time per instance.
Undergraduate Track — winning team:
Open Track — winning team:
Regardless of their final ranking, every participant receives:
Travel support is coordinated among SMIO, Hexaly, and the winning team during August and September 2026. The beneficiary is designated by the team itself; it is not transferable to people outside the registered roster.
In the event that no member of the winning team can travel to CSMIO 2026 for justified cause, the presentation slot may be covered remotely.
The following constitute grounds for disqualification:
Disqualification entails:
The disqualification of a team does not cause retroactive recomputation of the lead time of other teams. The historical BKS established by the disqualified team are retained as chronological milestones; the times that other teams would have held "in the absence" of the disqualified team are not credited retroactively.
Disqualification is declared by resolution of the Board of Directors, after a hearing of the affected team through the official contact channel. The team has 48 business hours to respond to the notice of grounds before the final decision.
Each team retains the intellectual property of its source code. SMIO and Hexaly do not request the delivery, disclosure, or licensing of the code.
By participating, each team grants SMIO a perpetual, non-exclusive, worldwide, and royalty-free license to:
Each team may freely publish analyses, comparisons, or academic articles based on its own work and its own solutions. It may not publish other teams' solutions without express authorization. It may reference the reference library by citing (dataset, year, instance number).
The license in favor of SMIO for the publication of the Method Descriptions is perpetual, non-exclusive, and with attribution to the team.
The 30 official instances are published under the following licenses:
The official channel for inquiries related to the Challenge is contacto@smiochallenge.com, with a subject line beginning with [Reto 2026].
These rules exist in Spanish and English versions. In case of discrepancy between the versions, the Spanish version prevails.
All deadlines and timestamps of the Challenge are recorded internally in UTC. The public interface also shows the time in America/Monterrey (UTC−6, no daylight saving).
Upon completing formal team registration, each member accepts these rules in their entirety. Acceptance is recorded electronically on the Platform.
SMIO processes participants' personal data in accordance with its privacy notice, available at smio.org. The data is used solely for the purposes of the Challenge and for SMIO's official communications.
Minimum structure:
SMIO × Hexaly Reto 2026 — Method Description
Team: [team name]
Category: [Undergraduate | Open]
Members: [list of names]
Guide: [name, Undergraduate Track only]
1. Problem formulation
[One or two sentences on which formulation was used,
if any: two-index MIP, set partitioning,
direct heuristic formulation, etc.]
2. General description of the method
[One paragraph. What does the method do? Is it exact,
heuristic, matheuristic, learning-based? What are its
main components?]
3. Tools and solvers
- Languages and libraries: [example: Python 3.11, NumPy, AMPL]
- Solvers: [example: Gurobi 11.0, Hexaly 14.0]
- Specific versions.
4. Hardware
- Cores: [example: 32 cores]
- RAM: [example: 128 GB]
- GPU: [if applicable, model and use]
5. Compute budget
- Typical time per large instance: [example: 2 hours per
3,000-customer instance]
6. References (optional)
[Prior work on which the method is based]
(Brief description, in PDF format)
| Event | Date |
|---|---|
| Public announcement at EPIO | April 22–24, 2026 |
| Release of the instance generator | June 8, 2026 |
| Opening of formal team registration | June 8, 2026 |
| Close of formal team registration | Start of the competition window |
| Start of the competition window | July 6, 2026 |
| Close of the competition window | August 1, 2026 |
| Publication of final results | August 2026 |
| XIV CSMIO · Challenge session, Hexaly workshop, ceremony | October 7–9, 2026 |
End of the Official Rules. SMIO Board of Directors, 2026.