Pipeline Speedup for a 6-Segment System (100 Tasks)
In pipelined processing, a workload’s total time is determined by the pipeline latency (time until the first result emerges) and the throughput (how often new results emerge after the pipeline is filled). For a pipeline with segments (stages) and clock cycle , the time to process tasks is typically modeled as:
The non-pipelined time for one task is given as seconds, so the non-pipelined time for tasks is:
The pipeline speedup ratio is then:
Key quantities:
- pipeline
- pipeline latency
- clock cycle
- speedup
Pipeline Latency & Throughput (Concepts)
For this problem:
- Non-pipeline time for one task: s
- Pipeline has segments:
- Clock cycle: s
- Number of tasks:
For a -stage pipeline:
- Latency (first task completion time in cycles) is stages
- Total cycles to process tasks is
A visual model of filling and draining:
Compute Pipeline Speedup for 100 Tasks
- 1Step 1
For tasks, each takes s without pipelining, so .
- 2Step 2
With pipeline segments, total cycles are .
- 3Step 3
Each cycle is s, so .
- 4Step 4
Use and simplify to get the numeric speedup.
1) Non-pipelined total time
2) Pipelined total time
Total number of cycles:
So total time:
3) Speedup ratio
Answer: The pipeline speedup ratio for 100 tasks is approximately .
Why it’s not a full $6\times$ speedup
For a 6-stage pipeline, the maximum ideal speedup approaches only for very large . With finite , the latency term () still matters: .
Assumption behind the formula
This model assumes the pipeline is balanced and runs at a steady clock where each stage takes exactly one clock cycle on average, so new tasks start each cycle after the pipeline fills.
Execution Time Comparison (100 Tasks)
Non-pipeline vs. 6-stage pipeline (10s clock)
Pipeline Timing for 100 Tasks (6 Stages)
Fill phase
Cycles 1 to 6First task moves through 6 stages; no completed results until after stage 6."
Steady phase
Cycles 7 to 105One task completes each cycle (every 10 seconds), producing throughput."
Drain complete
Cycle 105The 100th task completes; total cycles = 105."
Common Variations & Edge Cases
Knowledge Check
For a pipeline with segments processing tasks at clock cycle s, total pipelined time is:
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