org_roam/Uni/20250329121843-ise_week_2.org

ISE Week 2

• Different Configuration Sampling Methods (pages 8-19)
• Configuration Encodings (pages 21-28)
• Single Environment Learning (DaL) (pages 39-46)
• 2.1
  • Configuration Sampling
  • Binary Sampling Strategies
    • Option-wise Strategy
    • T-wise Strategy
    • Negative Option-wise Strategy
    • Random (Binary)
    • Difference Between Option-wise and Negative Option-wise Strategies
      • Option-wise Strategy
      • Negative Option-wise Strategy
      • Comparison Summary
  • Non-Binary (Numeric) Sampling Strategies
    • One-Factor-At-A-Time (OFAT)
    • Box-Behnken Design (BBD)
    • Central Composite Design (CCD)
    • Plackett-Burman Design (PBD)
    • Random (Non-Binary)
  • Mixed Variable Sampling
    • Example
• 2.2
  • Single Environment Learning: DeepPerf
  • Limitation of DeepPerf
  • Improved Approach: Divide-and-Learn (DaL)
    • Key Problem: Sample Sparsity
    • Key Properties of Configuration Landscape
    • Architecture of DaL
    • Trade-off: Number of Divisions
    • Results
• 2.3
  • Single Environment Learning: Encoding
    • Three Common Encoding Schemes
  • Encoding Schemes Explained
    • Label Encoding
    • Scaled Label Encoding
    • One-Hot Encoding
  • Community Debate and Justifications
  • Study Protocol

DONE Different Configuration Sampling Methods (pages 8-19)

DONE Configuration Encodings (pages 21-28)

DONE Single Environment Learning (DaL) (pages 39-46)

2.1

Configuration Sampling

In general machine learning problem, we dont care where the data comes from , but here we do.

Configuration sampling is used to select representative samples for learning performance models.

• Types of options:

  • Binary (e.g., on/off)
  • Numeric (e.g., value ranges)
• Goal: Balance model accuracy with sampling effort.

Binary Sampling Strategies

Option-wise Strategy

• Each binary option is selected at least once in some configuration.
• Minimize other options to reduce unknown interaction effects.
• Size: Linear in the number of binary options.

T-wise Strategy

• Covers all T-wise combinations of options (T ≥ 2).
• Example (2-wise): {001}, {010}, {100}, {111}
• Size: Exponential in T.

Negative Option-wise Strategy

• For each option: one configuration where it is disabled, all others enabled.
• Adds one all-yes configuration.
• Size: Linear.
• Example (3 options): {110}, {101}, {011}, {111}
• you can see the 4th one is an all-yes configuration

Random (Binary)

• Select n configurations randomly.
• Simple but may be less representative.

Difference Between Option-wise and Negative Option-wise Strategies

Both strategies are used for sampling configurations in systems with binary options, but they focus on different aspects of option selection.

Option-wise Strategy

• Goal: Ensure each option is enabled (selected) at least once across configurations.
• For every binary option, create a configuration where it is on.
• Other options are minimized to avoid unknown interactions.
• Focus: Testing the presence of each option.

• Example (3 options):

  • {100} → Option 1 enabled, others off
  • {010} → Option 2 enabled, others off
  • {001} → Option 3 enabled, others off

Negative Option-wise Strategy

• Goal: Ensure each option is disabled (deselected) at least once.
• For each option, create a configuration where it is off, and all others are on.
• Also includes a configuration where all options are on.
• Focus: Testing the absence of each option.

• Example (3 options):

  • {110} → Option 3 disabled
  • {101} → Option 2 disabled
  • {011} → Option 1 disabled
  • {111} → All options enabled

Comparison Summary

Feature	Option-wise	Negative Option-wise
Focus	Presence of each option	Absence of each option
What is varied	Each option enabled once	Each option disabled once
Other options in config	Typically disabled	Typically enabled
Additional config?	Not required	Yes, includes all-on config
Use case	Minimal presence testing	Influence of removing options

Non-Binary (Numeric) Sampling Strategies

One-Factor-At-A-Time (OFAT)

• Assumes no interactions among options.
• Varies one option at a time, others fixed at center values.
• Size: Linear in number of options.
• Example (values = 1,3,5): {333}, {533}, {133}, {353}, {313}, {331}, {335}

Box-Behnken Design (BBD)

• Captures quadratic effects and 2-wise interactions.
• Uses subset of 3^k full factorial (min, center, max).
• Size: Exponential in number of options.
• Example: {111}, {113}, {115}, {131}, {151}, etc.

Central Composite Design (CCD)

• Combines:

  • 2^k factorial points
  • 2k axial points at α-distance
  • 1 center point
• Captures curvature and interactions.
• Example: 8 full factorial + 6 axial + {333}

Plackett-Burman Design (PBD)

• Focus on main effects, assumes negligible interactions.
• Uses predefined seeds, e.g., PBD(9,3)
• First config from seed, rest by right-shifting seed.
• Uses indices only for values.
• Example: If O = {1,100,1000,10000,100000}, index 3 could mean 1, 1000, 100000

Random (Non-Binary)

• Random selection of numeric configurations.
• Risk of non-uniformity and clustering.
• Can negatively impact learning performance.

Mixed Variable Sampling

Some systems include both binary and non-binary (numeric) configuration options. These are referred to as mixed systems.

• Requires hybrid or combined strategies to ensure representative coverage.
• One approach: Permute over the mixed space by combining possible binary and numeric value combinations.
• This can grow combinatorially, so sampling techniques may be needed to reduce the total number of permutations.

Example

• Non-binary configs: {0.1, 0.4, 5}, {0.2, 0.4, 7}, {0.2, 0.7, 5}
• Binary configs: {1,0}, {1,1}

• Full mixed permutations:

  • {0.1, 0.4, 5, 1, 0}
  • {0.1, 0.4, 5, 1, 1}
  • {0.2, 0.4, 7, 1, 0}
  • {0.2, 0.4, 7, 1, 1}
  • {0.2, 0.7, 5, 1, 0}
  • {0.2, 0.7, 5, 1, 1}

2.2

Single Environment Learning: DeepPerf

Source: Ha & Zhang, ICSE 2019

DeepPerf is an early approach using deep neural networks (>3 layers) to predict software performance in configurable systems.

• Designed to address:

  • Small data size: Limited measurements available.
  • Feature sparsity: Only a few configuration options significantly impact performance.
  • Network instability: Tackled with tailored hyperparameter tuning.

Limitation of DeepPerf

• Does not handle sample sparsity, a major issue in configuration performance prediction.

Improved Approach: Divide-and-Learn (DaL)

Source: Gong & Chen, ESEC/FSE 2023

Key Problem: Sample Sparsity

• Caused by:

  • Inherited feature sparsity.
  • Small configuration changes leading to drastic performance shifts.
  • Not all configurations being valid.
• Training data is sparse due to expensive measurements.

Key Properties of Configuration Landscape

1. Intra-division smoothness: Configurations in the same division show smooth performance variations.
2. Inter-division sharpness: Cross-division configurations differ significantly, possibly on key options.

Risk: Limited data might lead to overfitting within divisions.

Architecture of DaL

Three Goals:

1. Divide the configuration data into meaningful divisions → function ϕ
2. Learn a local model for each division → function μ
3. Assign new configurations to the correct local model → using ϕ and μ

• Implementation:

  • CART (Decision Tree) is used for dividing.
  • DeepPerf models are trained within each division.
  • Random Forest is used for classifying unseen configurations into divisions.

Trade-off: Number of Divisions

• More divisions → better at tackling sparsity, but less data per model → risks underfitting.

• Need to balance:

  • Generalizability vs.
  • Specialization

Results

• DaL outperforms or matches state-of-the-art in 33 out of 40 cases.
• Achieves up to 1.94× improvement.
• Needs fewer training samples for same accuracy.
• Especially beneficial in complex systems or with more training data.

2.3

Single Environment Learning: Encoding

Source: Gong & Chen, MSR 2022

A study conducted by the lab investigates how different encoding schemes impact the software performance learning pipeline.

Three Common Encoding Schemes

• Label encoding
• Scaled label encoding (e.g., max-min normalization)
• One-hot encoding

Encoding Schemes Explained

Label Encoding

• Converts configuration options into numeric values.

• Example:

  • Configuration: (cache_size, interval, ssl, data_strategy)
  • Values: cache_size = (1, 10, 10000), interval = (1–4), ssl = (0, 1), data_strategy = (strategy_1, strategy_2, strategy_3)
  • Encoded: (10000, 2, 1, 1) → (2, 1, 1, 1) → data_strategy: (0, 1, 2)

Scaled Label Encoding

• Similar to label encoding but normalizes all values to the range [0, 1].
• Example (10000, 2, 1, 1) becomes (1, 1/3, 1, 0.5)

One-Hot Encoding

• Transforms each categorical value into a binary vector.
• Example: (10000, 2, 1, 1) becomes (0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0)

Community Debate and Justifications

• Categorical features (e.g., cache_mode = memory, disk, mixed):

  • Label encoding implies false ordering (1, 2, 3)
  • One-hot encoding avoids this but may introduce multicollinearity.

• Numeric options (e.g., cache_size = 1, 10, 10000):

  • Label encoding maintains order but struggles with large scale differences.
  • Scaled label encoding improves numeric stability but weakens interaction with binary features.

Study Protocol

• Evaluated using 7 learning algorithms across 5 software systems.