shift_schedule

Intelligent Shift Scheduling Engine

智能排班引擎

Motivation:

    In fast-paced industries such as manufacturing, healthcare, and transportation, where uninterrupted operations are crucial, shift schedules play a vital role. These schedules offer numerous benefits for both employees and employers. For employees, shift schedules provide the flexibility to balance personal or family obligations, improving work-life balance and overall job satisfaction. Meanwhile, employers benefit from the efficient use of facility and human resources.

    By implementing shift schedules, organizations can minimize downtime, maximize production capacity, generate increased revenue and provide better service. For instance, in manufacturing, with employees working in shifts, production can be optimized, leading to higher output and improved financial performance. In healthcare and emergency services, having a 24/7 operation is critical for ensuring the health and safety of the public. Shift schedules ensure that there are always qualified staff available to provide medical care and respond to emergencies.

    However, a satisfactory shift schedule can be extremely hard to create. On the other hand, no matter how perfect the first schedule is at the time of launch, frequent adjustments are usually inevitable due to unforeseen circumstances like an employee’s illness or a no-show. In order to efficiently respond to the events of each day and ensure that qualified staffs are always available to cover all shifts, we have designed and created this intelligent software for a wide range of shift scheduling applications. The software’s architecture is innovative, and it imaginatively blends artificial intelligence and combinatorial optimization techniques to deal with various shift scheduling problems.

Key Features:

• A wide variety of employee shift scheduling problems are classified by the same number of shifts set on every day in a schedule cycle. Currently, one to ninety six shifts per day are supported.
• This software is furnished with innovatively developed scheduling engines and modeling tools that make it easier for users to create, update, and iteratively optimize shift schedules. It is no longer necessary to build an LP, MIP, or CSP model for a shift scheduling problem. Instead, a problem model is built in a simpler, more user-friendly way by inputting parameters and constraints into a series of dialog boxes.
• It provides a collection of basic shift scheduling constraints for decision-making and model-building that are extracted and derived from common and frequently used schedule requests. Rather than being presented as mathematical formulas (e.g. a set of linear inequalities), these constraints are expressed by descriptive phrases in dialogs. Multiple basic constraints may be combined to generate more complex constraints to cope with the various requirements that arise in the real world.
• One of the most notable advantages this software delivers is its reactive scheduling capability, with which user can dynamically add or remove constraints to tackle the challenges of ongoing schedule adjustment. In order to create the least amount of perturbation when a new request comes in, a minimal number of altered shifts are sought in contrast to the existing schedule.
• Another characteristic of this software is its remarkable flexibility. It can be used to fulfill simple and complex scheduling tasks. The process of modeling, creating and revising schedules can be as easy as choosing an option and pressing a button. Moreover, sophisticated strategies and techniques are also available to deal with difficult issues (e.g., decomposition of a problem and merging multiple scheduling solutions to construct the final results).
• For each employee, his available dates, total working hours, total shifts, number of different shift types, and shift intervals are comprehensively considered and processed in a scheduling cycle. By using the estimation results and the optimization algorithm supplied in the software, it is effortless to determine the right number of employees with the necessary skills and experience in a schedule and achieve a healthy balance between company and employee needs.
• A cycle of a schedule may last one to thirty-one days. User can choose to terminate a scheduling process after one cycle of scheduling is complete or proceed to the next cycle. In the latter case, the software will take the outcomes of the preceding cycle into account and ensure that the shifts between cycles also satisfy the general constraints used inside a cycle.
• The scheduling outcomes will be shown in Gantt-charts and GUI tables. Integration tools are provided to communicate with external systems (e.g., import employee data into the software, export results to an excel file, and send results to employees via text message or social media. etc.).

Examples:

1. Creating a schedule for 9 employees over a 7-day period, subject to the following constraints:

• Each day is divided into three 8-hour shifts. Each shift type requires different number of employees.
  • A-shift：00:00-08:00（1 employee required）
  • B-sfhit：08:00-16:00（3 employees required）
  • C-shift：16:00-24:00（3 employees required）
• Every day, no employee works more than one shift.
• Number of shifts are evenly assigned to employees.
• Each employee has at least one day off in the 7-day period.

Software solution: In this shift schedule, 4 employees work for 48 hours and 5 employees work for 40 hours a week. The shifts assigned to each employee are spaced by at least 16 hours.

2. Creating a schedule for 10 employees over a 7-day period, subject to the constraints as listed in example 1.

Software solution: In this shift schedule, 9 employees work for 40 hours, 1 employee works for 32 hours a week. Each employee has at least two days off in the 7-day period and has different shift types on two consecutive days. The shifts assigned to each employee are spaced by at least 24 hours.

3. Creating a schedule for a hospital department over a 7-day period, subject to the following constraints:

• Each day is divided into three 8-hour shifts. Each shift type requires different number of employees on different level.
  • A-shift：23:30-07:30（1 Senior Nurse, 1 Nurse and 1 Assistant Nurse required）
  • B-sfhit：07:30-15:30（1 Senior Nurse, 3 Nurses and 2 Assistant Nurses required）
  • C-shift：15:30-23:30（1 Senior Nurse, 2 Nurses and 1 Assistant Nurse required）
• Every day, no nurse works more than one shift.
• No nurse works more than 40 hours in 7-day period.
• Number of shifts are evenly assigned to nurses.
• Each nurse has at least one day off in the 7-day period.
• Nurse01 and Nurse02 do not work on the same shift simultaneously.
• Arrange AssistantNurse1 to work with SeniorNurse1 simultaneously as much as possible

Software solution: In this shift schedule, the shifts assigned to each employee are different on two consecutive days, and they are spaced by at least 24 hours.

4. Creating a schedule for 35 employees over a 7-day period, subject to the following constraints:

• Every day is divided into six 4-hour time slots. Each time slot requires different number of employees.
  • A-slot：02:00-06:00（6 employees required）
  • B-slot：06:00-10:00（9 employees required）
  • C-slot：10:00-14:00（10 employees required）
  • D-slot：14:00-18:00（10 employees required）
  • E-slot：18:00-22:00（9 employees required）
  • F-slot：22:00-02:00（6 employees required)
• Every day, 5 shifts are arranged as shown in the table below, where each shift contains two 4-hour time slots:
• Every day, no employee works more than one shift.
• Each employee has two days off in the 7-day period.
• Number of shifts are evenly assigned to employees

Software solution: In this shift schedule, each employee works for 40 hours a week. The shifts assigned to each employee are different on two consecutive days, and they are spaced by at least 24 hours.

5. Creating a schedule for 13 employees over a 7-day period, subject to the following constraints:

• Each day is divided into three 8-hour shifts (Night, Day, Evening).
• The number of employees required for the same shift-type varies from day to day:
• 
• Every day, no employee works more than one shift.
• No employee works more than 40 hours in 7-day period.
• Number of shifts are evenly assigned to employees.
• Each employee has at least two days off in the 7-day period.
• Staff_3, Staff_4 and Staff_5 do not work on the same shift simultaneously.

Software solution: In this shift schedule, 3 employees work for 32 hours and 10 employees work for 40 hours a week. The shifts assigned to each employee are different on two consecutive days, and they are spaced by at least 24 hours.

6. Creating one day’s schedule for 7 employees in a retail store, subject to the following constraints:

• Personnel required may vary every half hour
• A minimum of 2 hours and a maximum of 4 hours constitute a shift
• Shift intervals must be at least half an hour
• Employees can work up to 8 hours per day and 40 hours per week
• Between 11:00 and 14:00, and between 17:00 and 20:00, everyone has at least a half-hour break (for lunch and dinner respectively)

One of the Software solutions: In this shift schedule, 4 employees work for 5.5 hours and 3 employees work for 6 hours a day (each colored batch represents a half-hour period).

7. Airport Personnel Scheduling

#### This example addresses a problem from the book ‘Introduction to Operations Research’, 7th edition, by Hillier/Lieberman.

• Cost control is the key to competing successfully in the airline industry. This problem focuses on how United Airlines schedules its employees to provide the necessary services to customers while minimising costs at the airport. The following table shows the cost per shift and the minimum number of employees required for each two-hour interval.
• Section 3.4 of the book describes a method for minimising total staffing costs and determining the number of employees required per shift (which can be implemented using the Python code included in the ‘Examples/Airport Staff Scheduling’ folder). Based on the results of the method, the minimum total staffing cost is $30,610 and the number of employees required per shift is 48 for shift 1, 31 for shift 2, 39 for shift 3, 43 for shift 4, 15 for shift 5. The number of employees required for each two-hour interval can be calculated to yield the results shown in the following table (e.g. from Noon to 2:00 P.M.: 48+31+39=118).
• The details of how to determine the minimum number of employees required for one day and how to deal with weekly days off are not explained (or published) in the book. Using the algorithms provided by our engine, we can conclude that the minimum number of employees required per day is 176. The optimal number of people required to meet the constraints of each employee having one day off per week and each employee having two days off per week is 206 and 247 respectively.
  • In the “Examples/Airport Staff Schedule” folder, you can find the Gantt-chart (GithubGC_176-1-12.png) and Excel (Personnel_Schedule_176-1-12.xlsx) of the daily schedule for 176 employees. Who is responsible for which shift can be adjusted according to employee preferences.
  • In the “Examples/Airport Staff Schedule” folder, you can also find the Gantt-chart (GithubGC_206-7-12.png) and Excel file (Personnel_Schedule_206-7-12.xlsx) of the weekly schedule for 206 employees. In this schedule, there are 202 employees who have one day-off a week and 4 employees who have two day-off a week. If 205 employees are arranged to participate in the schedule, 2 employees must work 7 days a week (no day-off). Considering the need to arrange employees to fill vacancies in case of emergencies, 206 employees are the best number of employees to meet the constraint of one day-off per week for each employee. In addition to this primary constraint, the schedule also ensures that each employee’s shifts are at least 12 hours apart from the previous day’s and the next day’s.
  • Here is the Gantt-chart of the weekly schedule for 247 employees. The corresponding Excel file (Personnel_Schedule_247-7-12.xlsx) can be found In the “Examples/Airport Staff Schedule” folder. In this schedule, 244 employees have two day-off a week and 3 employees have three day-off a week. If 246 employees are arranged to participate in the schedule, 2 employees must work 6 days a week (only one day-off). Considering the need to arrange staffs to fill vacancies in case of emergencies, 247 staffs are the best number of employees to meet the constraint of two day-off per week for each employee. In addition to this primary constraint, the schedule also ensures that each person’s shifts are at least 12 hours apart from the previous day’s and the next day’s. Any employee who works on shift 5 (from 10:00 pm to 6:00 am) one day will have the next day off. Note that, more constraints can be added to further improve the schedule.

Notes:

• R&D for the software is in progress. The code that’s been uploaded is incomplete.
• Please cite this repository by including the appropriate citation information when using content found here.

  Contact:

• Email:weiran@kpnmail.nl; weiran.aitech@gmail.com
• WeChat:wraitech