Approximate Computation

Why?: We can approximate calculations to sacrifice accuracy to save time, speed, and power.

e.g., search results don’t need to be 100% certain, you don’t need to play every frame of a video.

Approximate Half-Adder

Original

A	B	C	S
0	0	0	0
0	1	0	1
1	0	0	1
1	1	1	0

A	B	C	S
0	0	1	0
0	1	0	1
1	0	0	1
1	1	1	0

C = A XNOR B
S = A XOR B

Approximate Half-Adder Minus

Original

A	B	C	S
0	0	1	1
0	1	0	0
1	0	0	0
1	1	0	1

A	B	C	S
0	0	1	1
0	1	0	0
1	0	0	0
1	1	1	1

C = A XNOR B
S = A XNOR B

Approximate Half-Adder Plus

Original

A	B	C	S
0	0	0	1
0	1	1	0
1	0	1	0
1	1	1	1

A	B	C	S
0	0	0	1
0	1	1	0
1	0	1	0
1	1	0	1

C = A XOR B
S = A XNOR B

Approximate Half-Adder Minus Minus

Original

A	B	C	S
0	0	1	0
0	1	1	1
1	0	1	1
1	1	0	0

A	B	C	S
0	0	0	0
0	1	1	1
1	0	1	1
1	1	0	0

C = A XOR B
S = A XOR B