Strategic Code Deletion Michael Feathers R7K Research & - - PowerPoint PPT Presentation

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Strategic Code Deletion Michael Feathers R7K Research & - - PowerPoint PPT Presentation

Nov 30, 2022 123 likes •836 views

Strategic Code Deletion Michael Feathers R7K Research & Conveyance (everyone wants to delete code) When Can We Delete Code? Varieties of Useless Code And another one.. Low Value code No wikipedia entry (yet) :-) Coverage gprof

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Strategic Code Deletion

Michael Feathers

R7K Research & Conveyance

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(everyone wants to delete code)

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When Can We Delete Code?

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Varieties of Useless Code

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And another one..

Low Value code

No wikipedia entry (yet) :-)

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Coverage

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gprof

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https://nylas.com/blog/performance/

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Mutation Testing

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Feature Probe

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scythe_probe(“marker”);

Feature Probe

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scythe_probe(“marker”);

Feature Probe

  • Record marker
  • Periodically check for absence of marker
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Feature Probe

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Pricer Scan Devices Promotions Reconciliation Inventory Edge Client

  • Accept gift card
  • Split charge (2 customers)
  • Select home delivery
  • Produce/Meat by weight
  • Daily specials
  • Weekly specials
  • Restock perishable schedule
  • Record invalid scans
  • Change till procedure
  • Cashier login
  • Register reconcile
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The Cost Case

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Unreachable Code Dead Code Low Value Code

Compiler Errors / Warnings Mutation Testing Feature Probes / Stack Sampling / Coverage Delete on Detect Delete on Detect Strategize

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  • Delete Unreachable and Dead Code on Detection
  • Disable Low

Value Code at entry points

  • Verify in sample

Strategy

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Human in the Loop for Internal Pruning

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Systematic Rewrite

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Most rewrites are motivated by technology or architectural change

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Most rewrites are motivated by technology or architectural change

“Cleaning rewrites” should be focused and selective

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(from Jez Humble)

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Key Actions for Rewrite

  • Can you find all inputs and outputs?
  • Are you reducing conditionality?
  • Are you scoped for Characterization

Testing?

  • Can you run redundant?
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Searching for Pinch Points

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Characterization Testing

Tests you write to describe the current behavior of your system

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Characterization Testing

Tests you write to describe the current behavior of your system

How is this different from other testing?

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Is this a bug?

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Simple Case Heuristics

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  • Start with “x”
  • Use expressive (long) names
  • Rename to tell a story
  • Make the call on bugs
  • Be curious!

Simple Case Heuristics

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  • Start with “x”
  • Use expressive (long) names
  • Rename to tell a story
  • Make the call on bugs
  • Be curious!

Simple Case Heuristics

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  • Start with “x”
  • Use expressive (long) names
  • Rename to tell a story
  • Make the call on bugs
  • Be curious!

Simple Case Heuristics

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  • Start with “x”
  • Use expressive (long) names
  • Rename to tell a story
  • Make the call on bugs
  • Be curious!

Simple Case Heuristics

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  • Start with “x”
  • Use expressive (long) names
  • Rename to tell a story
  • Make the call on bugs
  • Be curious!

Simple Case Heuristics

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What was our goal?

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✔ balance ✔ gallons ✘ RESIDENTIAL_MIN ✘ RESIDENTIAL_BASE

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Tooling Varies

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Reducing Conditionality

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Apache

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Microsoft IIS

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if (…) { … }

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Edge-Free Programming

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Redund Until Replace

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Redund Until Replace

When you have a pure section of code that is a replacement, run it in parallel and log if there are differences

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Conclusion

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Pricer Scan Devices Promotions Reconciliation Inventory Edge Client

  • Accept gift card
  • Split charge (2 customers)
  • Select home delivery
  • Produce/Meat by weight
  • Daily specials
  • Weekly specials
  • Restock perishable schedule
  • Record invalid scans
  • Change till procedure
  • Cashier login
  • Register reconcile
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