Four-lane compare-exchange network
Sort four cards using the same five fixed compare-and-exchange stages.
Upper primary · about 9–12 · Logic & rule checking · Cooperation & communication
- Players
- Three roles per group
- Plan for
- 12–18 minutes
- Bring
- Per team: four large number cards 1,2,3,4, one four-lane mat, a five-stage log and pencil.
30 pupils: ten teams of three; operator moves cards, checker compares, recorder logs. Rotate after a run.
Prepare
Lay lanes 1,2,3,4 left to right. Put one distinct number card in each. Write the fixed stage list: (1,2), (3,4), (1,3), (2,4), (2,3). Lane labels stay fixed; they are not the card values.
Play
At each stage compare only its two lanes. Put the smaller card in the lower-numbered lane, larger in the higher-numbered lane; if already ordered, do not swap. Copy all four values into that stage’s row, then continue. Never choose a different pair to repair a mistake silently.
Example
Start 4,1,3,2. The five resulting rows are 1,4,3,2 → 1,4,2,3 → 1,4,2,3 → 1,3,2,4 → 1,2,3,4. At stage 3, lanes 1 and 3 already hold 1 and 2, so no swap.
Finish
Success means a correctly logged run ending 1,2,3,4. If not, find the first row that broke its comparison rule, reset there and retry. Rotate roles and try another starting permutation. No fastest-team award.
Adapt
Adult reads card values; use large high-contrast numerals. Teams may first compare just one pair. Cards 1–4 are distinct in this version; do not add equal or negative values without explaining the changed task.
Purpose and provenance
Activity aim: Sort four cards using the same five fixed compare-and-exchange stages.
Practice opportunities: Applying one local comparison rule consistently, logging intermediate states and checking a final order.
What adults can observe: Ask why a swap was or was not made at a stage; one successful run does not establish a general proof.
Mechanism and our adaptation: PartyPageKit classroom adaptation of a common activity mechanism. The earliest inventor has not been established; the linked references are identified separately by the editor.
Reference: CS Unplugged — Sorting Networks: What’s it all about? — Comparator-network background; our four-card, five-comparison table is independently drawn and checked over all 24 permutations.
These are planning aims and observable actions, not measured lasting gains. The reference is not an endorsement or a test of our adaptation.
Free material alternatives: Write numbers on four large scrap-paper cards and draw four lanes with a ruler.
Buying links: reserved; no purchase is required.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. Use only the pages needed for the chosen version; oral and movement activities may need no printing.
Player four-lane mat and cards
Lanes 1–4 remain fixed. Cut the four number cards with adult help and place in any order. At each pair, smaller value goes to the lower lane number.
| 1 | 2 | 3 | 4 |
|---|---|---|---|
| ________ | ________ | ________ | ________ |
Player five-stage log
Write the start and all four values after every stage. Fixed pairs: (1,2), (3,4), (1,3), (2,4), (2,3).
| Stage | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Start | ____ | ____ | ____ | ____ |
| 1 (1,2) | ____ | ____ | ____ | ____ |
| 2 (3,4) | ____ | ____ | ____ | ____ |
| 3 (1,3) | ____ | ____ | ____ | ____ |
| 4 (2,4) | ____ | ____ | ____ | ____ |
| 5 (2,3) | ____ | ____ | ____ | ____ |
Teacher instructions and key · keep separate
30 pupils: ten teams of three; operator moves cards, checker compares, recorder logs. Rotate after a run.
Per team: four large number cards 1,2,3,4, one four-lane mat, a five-stage log and pencil.
Write numbers on four large scrap-paper cards and draw four lanes with a ruler.
Preview one copy. Print only required player pages; keep this teacher page out of player packets. Give children the choice to watch, pause or use the described adaptation. These are activity practice opportunities, not measured developmental outcomes.
| State | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Start | 4 | 1 | 3 | 2 |
| (1,2) | 1 | 4 | 3 | 2 |
| (3,4) | 1 | 4 | 2 | 3 |
| (1,3) | 1 | 4 | 2 | 3 |
| (2,4) | 1 | 3 | 2 | 4 |
| (2,3) | 1 | 2 | 3 | 4 |
All 24 distinct permutations of cards 1–4 finish 1,2,3,4 under these stages (checked by enumeration). This is the teacher’s verification, not a claim that one pupil run proves it.