pycsp3 fails to solve anything

[felixbinder]

I am using Python 3.9.7 on MacOS 12.4 (21F79) on Apple Silicon. Trying to solve anything will result in UNKNOWN returned by the solver. The solver log file is empty.

To reproduce, the following example from the documentation fails to work:

from pycsp3 import *

n = 4
R, G, B = colors = 0, 1, 2

# x[i] is the color of the ith node
x = VarArray(size=n, dom=colors)
print("Array x: ", x)
print("Domain of any variable: ", x[0].dom)
satisfy(
    x[0] != x[2],

    x[1] != x[3]
);
if solve() is SAT:
    print(values(x))
satisfy(
    x[0] != x[1],

    x[1] == x[2],
    
    x[2] != x[3],
    
    x[3] == x[0]
);
if solve() is SAT:
    print(values(x))
if solve(sols=ALL) is SAT:
    print("Number of solutions: ", n_solutions())
print(solve())
```.

Running this results in the following output:

(base) felixbinder@Felixs-MacBook-Pro tools_block_construction_human_experiments % /Users/felixbinder/opt/anaconda3/bin/python "/Users/felixbinder/Cloud/Grad School/Fan L
ab/Block_Construction/tools_block_construction_human_experiments/stimuli/BIBD_test_main.py"
Array x: [x[0], x[1], x[2], x[3]]
Domain of any variable: 0 1 2
UNKNOWN

I've installed pycsp3 by running `sudo pip3 install pycsp3`. 

[felixbinder]

I originally did not have Java installed, but after installing the latest Java from oracle.com nothing has changed (JRE).

[felixbinder]

And I see the same behavior for both ACE and choco

[felixbinder]

Update: after installing the Java Development Kit 18 it now works. Feel free to close this issue, but I am leaving it open to suggest that you add error messages if JDK is not installed and as note clearly in the documentation that JDK needs to be installed (I only saw it in the Windows install section—macOS doesn't include it anymore, I believe).

[xcsp3team]

I will try to think about this at the next update of the doc.