Can't multiply sparse logical matrices?

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Nachiketa Sahoo
Nachiketa Sahoo 2012-6-13
编辑： Thomas Richner 2017-12-12
Is there a way to multiply sparse logical matrices? I guess I am looking for a space efficient way to multiply matrices that contain only 0/1?
>> m = magic(5)
m =
17 24 1 8 15
23 5 7 14 16
4 6 13 20 22
10 12 19 21 3
11 18 25 2 9
>> a = m>5
a =
1 1 0 1 1
1 0 1 1 1
0 1 1 1 1
1 1 1 1 0
1 1 1 0 1
>> b = m>10
b =
1 1 0 0 1
1 0 0 1 1
0 0 1 1 1
0 1 1 1 0
1 1 1 0 0
>> a+b
ans =
2 2 0 1 2
2 0 1 2 2
0 1 2 2 2
1 2 2 2 0
2 2 2 0 1
>> a*b
Error using *
Both logical inputs must be scalar.
To compute elementwise TIMES, use TIMES (.*) instead.

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回答（2 个）

the cyclist
the cyclist 2012-6-13
The short answer is "no". However ...
I asked about multiplication of logical matrices a while back. There were some answers that might be helpful to you in the thread:
http://www.mathworks.com/matlabcentral/answers/5672-speed-up-a-logical-matrix-multiply
Thomas Richner
Thomas Richner 2017-12-12
编辑：Thomas Richner 2017-12-12
I too would love to multiply sparse logical matrices. I was completely surprised it wasn't implemented. The solution is to convert the smaller matrix to a sparse double with double(). Also note that sparse singles don't exist. I imagine as Matlab tries to keep pace with Deep Learning, they will need to add sparse singles, sparse logical multiplication, and half precision types.

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