The document discusses optimization techniques used in Angular and React to improve performance. It explains that both frameworks use monomorphic property access by enforcing that all view/fiber nodes share the same "hidden class" or shape. This avoids expensive property lookups and allows properties to be accessed over 10,000 times faster. The document also discusses how bit fields and bit masks are used to efficiently represent side effects and other metadata in React fiber nodes. Bloom filters are mentioned as something Angular uses in its dependency injection system.

1. Why Angular and React are so fast?
Max Koretskyi aka Wizard
Developer Advocate

2. 2015 20162014 2017 2018
A failed startup
that made me
learn to program
and gave broad
programming
experience
SO activity that
build my
knowledge base
and created a
foundation for
blogging
Angular In Depth
that helped me
build strong
community
and establish
reputation as an
Angular expert
Public speaking
that helped me
meet awesome
people and
become GDE and
MVP
Developer Advocate
job that allows me to
to develop
programming and
marketing skills at
the same time
My 5 years in IT

3.  maxkoretskyi.com/connecting-the-dots
 https://youtu.be/fT9CZ2QZx5A
Find out more at

4. Benedikt Meurer, V8 optimizations lead engineer
Alex Rickabught, Angular core team
Dan Ambramov, React core team
Monomorphism Bit fields & Bit masks Bloom filters
Kudos to
Optimization techniques in Angular and React

5. We use one type for all View nodes so that property
access in loops stay monomorphic!
Misko Hevery, technical lead of Angular
Angular sources comments

6. Fiber node … shares the same hidden class.
Never add fields outside of construction in `ReactFiber`
Contributing To React Fiber guidelines
Sebastian Markbåge, technical lead of React

7. • What is a fiber node in React & a view node in Angular?
• What is hidden class and why is it shared by fiber and view nodes?
• What is monomophic property access and why is it important?
Questions we need to answer

8. Representing a template in Angular
@Component({
template: `
<h1>The title is: {{title}}</h1>
<h2>My hero is: {{hero}}</h2>
`
})
export class AppComponent {
title = 'Tour of Heroes';
hero = 'Windstorm';
}
Type: h1
Type: h2
View Nodes
bindings: {
text: "Tour of Heroes"
}
bindings: {
text: " 'Windstorm"
}

9. Representing a template in React
class App extends Component {
state = {
title: 'Tour of Heroes',
hero: 'Windstorm'
};
render() {
return (
[
<h1>The title is: {this.state.title}</h1>,
<h2>My hero is: {this.state.hero}</h2>
]
)
}
}
Type: h1
Type: h2
props: {
children: "Tour of Heroes"
}
props: {
children: " Windstorm "
}
Fiber Nodes

10. Fiber and View nodes are used a lot
when processing changes
properties could easily be accessed
over 10 000* times
function updateNode(node, …) {
let value = node.property;
}
*100 components x 10 elements x 10 function calls

11. Locating value of an object's property
in memory
is a complicated process

12. let object = { x: 5, y: 6 };
JSObject
5
6
Property information
Offset: 0
[[Writable]]: true
[[Enumerable]]: true
[[Configurable]]: true
Shape
'x'
'y'
Property information
Offset: 1
[[Writable]]: true
[[Enumerable]]: true
[[Configurable]]: true
Shapes aka Hidden Class (Maps in V8)

13. 5
6
JSObject a
Property
information
Shape
'x'
'y'
Property
information
JSObject b
7
8
let a = { x: 5, y: 6 };
let b = { x: 7, y: 8 };
Shapes help reduce memory footprint

14. let a = { x: 5, y: 6 }
let b = { x: 7, y: 8 }
b.z = 9;
b.y = 10;
JSObject a
5
6
Shape
'x'
'y'
JSObject b
7
8
Shape
'z'
Shape
'y'
9
10
Transition chains

15. Inline Caching (IC)
to the rescue

16. Monomorphic property access
getX(a);
getX(b);
getX(c);
function getX(o) { return o.x; }
let a = { x: 5, y: 6 };
let b = { x: 7, y: 8 };
let b = { x: 7, y: 8 };
a function only saw one type of a shape

17. Polymorphic property access
getX(a);
getX(b);
getX(c);
getX(D);
function getX(o) { return o.x; }
let a = {x: 5, y: 6};
let b = {y: 7, x: 8}; // different order
let b = {y: 7, x: 8, z: 5}; // new properties
let d = Object.create({}, {}; // different prototype
a function only saw up to 4 different types of a shape

18. Megamorphic property access
Monomorphic prop access maybe
up to 100 times faster than
megamorphic.
a function saw more than 4 different types of a shape

19. Frameworks enforce
the same shape (hidden class)
for fiber and view nodes
to enable monomorphic property access

20. Template node types
Fiber node (React) Template element View node (Angular)
HostComponent HTMLElementNode TypeElement
HostText HTMLTextNode TypeText
FunctionComponent,
ClassComponent
Component Component

21. type Element {
fieldA;
fieldB;
}
type Text {
fieldC;
field;
}
type Component {
fieldE;
fieldF;
}
Property access is not monormophic
type Node {
tag: nodeType;
fieldA | null;
fieldB | null;
fieldC | null;
fieldD | null;
fieldE | null;
fieldF | null;
}
Property access is monormophic

22. function beginWork(fiberNode, ...) {
...
switch (fiberNode.tag) {
case FunctionalComponent: {...}
case ClassComponent: {...}
case HostComponent:
return updateHostComponent(fiberNode, ...);
case ...
Branching by node type in React

23. Bit fields (vector) & Bit masks

24. Bit field is just an array of bits
let effectTag = 0b01010001; // 81
0 1 0 1 0 0 0 1

25. Side effects in React fiber are
encoded using bit fields
0 1 0 1 0 1 0 0
Placement
Update

26. Effects in React Fiber architecture
• Render phase
• Process changes from setState
• Update props on child elements
• Call lifecycle methods (shouldComponentUpdate etc.)
The result of the phase is a tree of fiber nodes marked with side-effects.
• Commit phase (apply effects)
• Update DOM
• Call lifecycle methods (componentDidUpdate etc.)
• Update refs

27. Before render phase: After render phase:
4..toString(2) = 100
type: 'span'
effectTag: 0
type: 'span'
effectTag: 4
const effectTags = {
Placement = : 0b000000000010;
Update : 0b000000000100;
PlacementAndUpdate : 0b000000000110;
...
}

28. let effectTag = 0b00000000;
0 0 0 0 0 0 0 0
effectTag = effectTag | effectTags.Update;
0 0 0 0 0 1 0 0
isUpdateEffectSet = !! (effectTag & effectTags.Update);
Write with bitwise OR
Define bitfield
Check with bitwise AND

29. Branching by effect in React
function updateHostEffects(fiberNode) {
...
const effectTag = fiberNode.effectTag;
if (effectTag & effectTags.Placement) { ... }
if (effectTag & effectTags.PlacementAndUpdate) { ... }
if (effectTag & effectTags.Update) { ... }
...
}

30. Encoding objects in bit fields
let user = {
first: true,
group: 20,
sortKey: 347843
};
allocations in memory for:
• a standard JS object
• 3 strings for the keys
• 3 values stored in the keys

31. Encoding objects in bit fields
Field Restrictions on values Bits required
sortKey less than 1M 20 (220 > 1M)
group less than 50 6 (26 = 64)
first boolean 1
00000 0 000000 0000000000000000000
sortKeygroupfirst
32 bits

32. Encoding objects in bit fields
let user = 0x 05454ec3;
let user = 0b 00000 1 010100 001010100111011000011;
let user = { first: true, group: 20, sortKey: 347843 };
Field Decimal Binary
sortKey 347843 001010100111011000011
group 20 010100
first true 1

33. Why bother?

34. • millions of allocations of keys,
objects and values
• a ton of GC (garbage collection)
cleanup after each iteration
• larger and fragmented memory
usage
1 million of objects require
VS
• one typed array for one million
32-integer values
• alsmot zero garbage collection
• smaller and contiguous memory
usage.
Regular JS object Encoded in a bitfield

35. Bloom filters
is element in the set?
DEFINITELY NO MAYBE
100% probability varying probability
data structure that answers the question

36. 0 1 0 0 0 0 1 0
Is element in a set? Is bits [n1,n2…n] set?
Each element is encoded in a bit field
let value = "Jonh";
calculateBit1Number(value); // 2
calculateBit2Number(value); // 7

37. John - 2
0 0 0 0 0 0 0 1
0 0 0 0 1 0 0 0
0 0 0 0 0 0 1 0
Using bloom filter for string values
Anna – 1
Tom - 4
[ "John", "Anna", "Tom" ]
let calculateBit1Value = (value) => value.charCodeAt(0) % 8

38. Why "yes" is not guaranteed?

39. Anna – 1 0 0 0 0 0 0 0 1
0 0 0 0 1 0 0 0
0 0 0 0 0 0 1 0
0 0 0 0 0 0 1 0
collisions
Tom - 4
John - 2
Jane - 2
Less slots, more collisions

40. How to increase
probability of "Yes"?

41. Anna – 1, 6 0 0 1 0 0 0 0 1
0 1 0 0 1 0 0 0
0 0 0 0 0 0 1 1
0 1 0 0 0 0 1 0
no
collisionsTom – 4, 7
John – 2, 7
Jane – 2, 1
More slots, less collisions

42. Where does Angular use this?
Dependency Injection
mechanism

43. ServiceA
ServiceB
ServiceC
constructor( ServiceA ) {}
Injector
ServiceD

44. Hierarchical
injectors
Dashboard
component
Widget
component
SiteAnalytics
component
WidgetManager
Injector
Injector
WidgetManager
Injector
Is here?
no – go up
Is here?
no – go up
Is here?
yes – resolve

45. Bloom
filters
Injector
Dashboard
component
Widget
component
SiteAnalytics
component
WidgetManager
WidgetManager
Injector
Is here?
no – go up
Is here?
no – go up
resolve
Injector
Bloom
filter
Bloom
filter
Bloom
filter
Is here?
maybe –
chec injector

46. Ask me anything

47. Angular In Depth
conference
Kyiv,
15th of June

48. Follow me to learn fundamentals
@maxim_koretskyi
maxkoretskyi
maxkoretskyi.com