Parallel Computer Architecture

844

CHAPTER

11 Latency Tolerance

Time

in

processor's critical path

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EL

y**t*m

c

a

o

c

I o

c

o

c

! c

c

(a) Baseline communication,

no

latency tolerance

IE Wx'Ma

ZEH

CA

N

^

tiAjAMM

(b) Single large message, no overlap with computation

P

CA

N

S

Î

1

i i-waxixai

ι

(c) Single large message, overlap with computation

m

sa

kääSi

tz:]

Θ

Local computation (c

a

,

c

c

)

Endpoint processor overhead

Assist occupancy

Network delay

Bandwidth-related time

P

CA

N

Ρ71

eS

BS7S

Î

El

i

i«

x

m

MM

>«

(d) Word-size overlapped messages, no overlap with computation

P:

CA:

ñ ñ ñ

N:

Ü

ta

WJgJSL

MVIVISI

BfV^I

(e) Word-size overlapped messages, overlap with computatio ...