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• I have searched the existing issues for a bug report that matches the one I want to file, without success.

Did you read the documentation and troubleshoot guide?

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Environment

- **OS**: MacOS 13.3.1
- **Sage Version**: 9.8

Steps To Reproduce

Below is an example of code that leads to the problem. The problem occurs even in this very simple case where the computations are simple:

Parallelism().set(nproc=2) # Setting this to anything other than 1 leads to a problem
var('m')
M=Manifold(4,'M')
X.<t,r,th,ph>=M.chart(r't r:(0,oo) th:(0,pi):\theta ph:(0,2*pi):cyclic:\phi')
Y.<rho,t1,th,ph>=M.chart(r'rho:(0,oo) t1:\tilde{t} th:(0,pi):\theta ph:(0,2*pi):cyclic:\phi')
X_to_Y=X.transition_map(Y,[1/sqrt(r^2-t^2),t/sqrt(r^2-t^2),th,ph])
X_to_Y.inverse()
g=M.metric('g')
g[0,0]=-(1-2*m/r)
g[1,1]=(1-2*m/r)^(-1)
g[2,2]=r^2
g[3,3]=r^2*sin(th)^2
g.display()
g.display(Y) # Problem occurs at this point, when some computation must happen in the background to calculate the components of the metric in the chart Y

Expected Behavior

The code should display the expression of the metric in the chart Y.

Actual Behavior

If nproc is set to anything other than 1, Sage prints the attached text and hangs on the command.

SageErrorMessage.txt

Additional Information

No response