Equivalent of A&(~B) without using ~

2 次查看（过去 30 天）
Yi-xiao Liu
Yi-xiao Liu 2022-6-22
评论： Yi-xiao Liu 2022-6-22
I am looking for a way to generate the same output as A&(~B) w/o using the ~ operator. The problem is both A and B are very large sparse matrices with only a few non-zero elements (trues). Evaluating ~B will produce a temporary matrix that cannot fit in memory. What's the best way to circumvent this?

请先登录，再回答此问题。

采纳的回答

Yi-xiao Liu
Yi-xiao Liu 2022-6-22
编辑：Yi-xiao Liu 2022-6-22
Ran in:
Hat tip to @David Goodmanson and @Stephen23. I found 4 solutions:
A=rand(5)<0.6;B=rand(5)>0.2;
ref=A&(~B);
Method1=A;
Method1(B)=false;
Method2=A-(A&B);
Method3=(A-B)>0;
Method4=xor(A,A&B);
all((Method1==ref)&(Method2==ref)&(Method3==ref)&(Method4==ref),"all")
ans = logical
1
rng("shuffle")
t1=nan(10,1);t2=nan(10,1);t3=nan(10,1);t4=nan(10,1);
for ii=1:10
idx=ceil(1e6*rand(2e6,2));
idx=unique(idx,"rows");
i=idx(:,1);j=idx(:,2);
A=sparse(i(1:1e6),j(1:1e6),true(1e6,1),1e6,1e6);
B=sparse(i((1e6+1):end),j((1e6+1):end),true(numel(i)-1e6,1),1e6,1e6);
tic
Method1=A;
Method1(B)=false;
t1(ii)=toc;
tic
Method2=A-(A&B);
t2(ii)=toc;
tic
Method3=(A-B)>0;
t3(ii)=toc;
tic
Method4=xor(A,A&B);
t4(ii)=toc;
end
t1=mean(t1);t2=mean(t2);t3=mean(t3);t4=mean(t4);
bar([t1,t2,t3,t4])
Personally I like the 4th one the most. It's fast, it's short, and it does not invoke type conversion in case you are short on Bytes.
  4 个评论
显示 2更早的评论
Paul
Paul 2022-6-22
编辑：Paul 2022-6-22
I thought there was a concern about memory consumption, so thought it worthwile to point out that Method2 requires 8x more memory, in addtion to the need to cast to logical if used later on as logical.
Yi-xiao Liu
Yi-xiao Liu 2022-6-22
@Paul You are absolutely right. This is in fact (one of) the reason I prefer method 4 (see last line of my answer).
On conversion back to logical, my experience is that MATLAB will do the conversion for you if you try to use double as logical. there is no need to do it explicitly.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Mathematics and Optimization 的更多信息

标签

产品


版本

R2019b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by