Yes, I tried this method and it got resolved.
Btw, may I check another issue, Nick?
Which method? There were two proposed which is why I asked again.
If the sentence below gave me the previous error message, does that mean the problem is not caused by index type, but out of memory? Kindly let me know your thoughts.
debug> size(Bf(:, noref))
debug> size(Bbus(noslack, noref))
Assuming Bf and Bbus are themselves not sparse arrays, then yes, it appears to be an out of memory problem. If they are 8 byte data types, then
Bf = 84450 x 67518 =5.7e elements x 8 bytes = 46.5e9 bytes = 42.5GB
Bbus = 67518 x 67518 = 4.5e9 elements x 8 bytes = 36.5e9bytes = 34GB