Can't multiply sparse logical matrices?

Question

Nachiketa Sahoo 2012-6-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41084-can-t-multiply-sparse-logical-matrices

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.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

the cyclist 2012-6-13

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41084-can-t-multiply-sparse-logical-matrices#answer_50654

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

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Thomas Richner 2017-12-12

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/41084-can-t-multiply-sparse-logical-matrices#answer_295932

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.