Schedule Editing: Forced vs Preferred Shifts

🎯 Introduction - Why it matters?

Efficient schedule editing is crucial for any organization working with shift-based schedules. The ShiftGo.site system provides two powerful mechanisms for schedule modification: forced shifts and preferred shifts.

💡 Key insight

Understanding the difference between "what MUST happen" (forced) and "what we WANT to happen" (preferred) is the foundation of effective schedule optimization.

According to industry research, organizations that use intelligent constraint systems reduce schedule planning time by up to 85% while improving worker satisfaction through fairer shift distribution.

🧠 Basic concepts and differences

🔴 Forced shifts

Definition: Hard constraints that the solver MUST satisfy

Visual indicator: Red border in the table

Behavior: Cannot be changed by the optimizer

Use case: Vacations, training, mandatory assignments

Risk: Too many can lead to INFEASIBLE solutions

🟢 Preferred shifts

Definition: Soft constraints the solver tries to maintain

Visual indicator: Green border in the table

Behavior: Can be changed if necessary

Use case: Maintaining current schedule stability

Benefit: Provides flexibility while minimizing changes

🔄 How the system processes constraints

Hard constraints first: The solver ensures all forced shifts are satisfied
Soft optimization: Among valid solutions, it minimizes penalties for changing preferred shifts
Balancing: It considers other constraints (weekends, shift balance) within the remaining flexibility

🔴 Forced shifts (Hard constraints)

Forced shifts represent absolute requirements that cannot be violated. The optimization engine treats these as immutable facts when generating schedules.

🎯 When to use forced shifts:

Vacations and leaves: When an employee is unavailable
Training sessions: Mandatory attendance requirements
Special assignments: Specific worker needed for particular shift
Past days: Already worked shifts that cannot be changed
Legal requirements: Compliance-driven assignments

⚠️ Important: INFEASIBLE risk

Too many conflicting forced shifts can make the schedule impossible to solve. Always verify that your hard constraints are compatible with workforce capacity and other system requirements.

🛠️ How to set forced shifts:

Click on the table cell you want to constrain
Click multiple times until you see a red border
The cell will show the forced assignment (R/E/N/-)
Run the solver - it will respect this constraint

🟢 Preferred shifts (Soft constraints)

Preferred shifts are the system's way of maintaining schedule stability. They tell the optimizer "try to keep this assignment, but change it if necessary for a better overall solution."

🎯 When to use preferred shifts:

Current schedule preservation: When making minor adjustments
Worker preferences: Accommodating (non-mandatory) requests
Historical patterns: Maintaining proven shift distributions
Gradual changes: Implementing modifications step by step
Experimentation: Testing schedule variations safely

💡 The "Prefer Entire Table" feature:

This powerful button converts your current schedule into preferred shifts for all cells. Perfect for when you want to make targeted changes while keeping most of the schedule intact.

🔄 Workflow tip

1. Set forced shifts for absolute requirements
2. Click "Prefer Entire Table" to preserve current assignments
3. Run solver to get optimal solution with minimal disruption

⚖️ Penalty system and optimization

The system uses a sophisticated penalty matrix to calculate the "cost" of changing preferred shifts. Lower penalties make changes more likely, higher penalties make the system work harder to avoid them.

📊 Penalty matrix for shift changes:

From Shift	To Shift	Penalty	Explanation
Morning	Morning	0	No change - no penalty
Evening	Evening	0	No change - no penalty
Night	Night	0	No change - no penalty
Free	Free	0	No change - no penalty
Evening	Night	3	Low cost - natural progression
Morning	Evening	5	Moderate cost
Evening	Morning	5	Moderate cost
Night	Evening	8	Medium cost
Morning	Night	15	High cost - major change
Night	Morning	15	Very high cost - worst change
Morning	Free	2	Low cost for giving up shift
Evening	Free	2	Low cost for giving up shift
Night	Free	2	Low cost for giving up shift
Free	Morning	10	Medium cost for adding shift
Free	Evening	10	Medium cost for adding shift
Free	Night	10	Medium cost for adding shift

🧮 Penalty matrix logic:

No change (0): Keeping the same shift costs nothing
Natural progressions (3): Evening → Night is natural sequence
Moderate changes (5): Morning ↔ Evening
Difficult transitions (15): Morning ↔ Night is the biggest jump
Giving up work (2): Low cost for freeing up worker
Adding work (10): Medium cost for additional shift

⚙️ Penalty weight configuration

The global penalty multiplier can be adjusted in the constraints configuration. Higher weight = greater emphasis on maintaining preferred shifts.

🔄 Practical workflow for editing schedules

📋 Scenario: Modifying existing schedule

Step 1: Secure the past

For all days that have already been worked (e.g., May 1-15), set forced shifts by clicking cells to red borders. This locks past changes.

Step 2: Force new requirements

For future days where you MUST introduce changes (vacations, training), set forced shifts with red borders.

Step 3: Prefer current schedule

Click "Prefer Entire Table" - system will set current schedule as preferred shifts (green borders) for all remaining cells.

Step 4: Optimize

Run solver. It will find solution that:

✅ Satisfies all forced shifts (red)
🎯 Minimizes changes to preferred shifts (green)
⚖️ Balances other constraints (weekends, shift balance)

Step 5: Analyze report

After generation, check the differences report - shows which workers were affected by changes and what type. Use this to communicate changes to team.

💡 Use case examples

🔴 Forced shifts example

Situation: Unexpected leave

Problem: John Smith suddenly fell ill and cannot work May 10-12.

Solution:

Click John's cells for days 10-12 May
Set red border with "-" (all shifts forbidden)
Press "Prefer Entire Table"
Run solver

Result: System finds new schedule without assigning John any work on those days, even if it requires reorganizing other workers.

🟢 Preferred shifts example

Situation: Minor schedule adjustments

Problem: June schedule is OK, but need to add one worker to June 15 morning shift.

Solution:

Set forced shift (red) for additional worker on 15.06 morning
Press "Prefer Entire Table"
Run solver

Result: System changes minimal number of assignments to add required worker, preserving as much of current schedule as possible.

🎯 Key difference in results

Forced shifts: "Must happen, regardless of consequences"

Preferred shifts: "We want it to happen, but can change if needed"

🏆 Best practices

✅ Do:

Use forced shifts: Only for absolute requirements
Lock the past: Always set forced shifts for already worked days
Test step by step: Add constraints gradually
Check differences report: Analyze what changes were made
Communicate changes: Inform workers about modifications
Backup schedule: Save schedule before major changes

❌ Avoid:

Over-constraining: Too many forced shifts can lead to INFEASIBLE
Ignoring penalties: Check change costs in report
Frequent rewrites: Better to modify than start from scratch
Mixing modes: System won't allow using both preferred and forced on same cell
Forgetting validation: Check if schedule meets all legal requirements

⚠️ Troubleshooting: What to do when INFEASIBLE?

Check conflicts: Are forced shifts contradictory?
Count resources: Do you have enough workers for required days?
Check weekends: Do weekend constraints conflict with forced shifts?
Reduce forced shifts: Temporarily remove some red constraints
Increase flexibility: Change some forced shifts to preferred

🎯 Golden rule

"Forced shifts for what MUST happen, preferred shifts for what you WANT to happen"

This simple rule will help you avoid most configuration problems with schedules.

📚 Related articles

⚖️ Excel vs shift scheduling systems

Comparison of traditional methods with modern systems

🚀 Schedule optimization

Advanced techniques for creating efficient schedules

Coming soon

⚖️ Labor law and schedules

Legal compliance in shift work planning