How to read and write variable in omniverse composer action graph?

I am using write node of a variable for dynamically changing the value of it.
When I click “play” of the stage, the write node input is dynamically changing, but the output is still 0.
Then I drag another read node of variable, the value is still 0.
So how can I read and write a variable value in Omniverse Action Graph

These are the screenshot of my variable input and output node

Thanks that helps. Let me find out

Can you send us your USD file. We are unable to reproduce your error

Btw, is there any “greater than” node, “less than node” and “equal” node in action graph? I didn’t find them in “Math”. (166.5 KB)
The zip file contains the USD file. And I used a Backdrop to highlight the problem part. @Richard3D

The write node input is a normalized 3D vector, I think the input is correct, but both nodes output is (0,0,0). Then I try to change the default value of relative vector (my variables) to (1,2,3). The read node output is still (0,0,0) @Richard3D