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bugs - Instant kernel crash when using `+=` on `SparseArray` with repeated entries



Bug introduced in 5.2 and fixed in 10.1.0



Not sure if this is known behavior or not, but the following two lines produce an instant kernel crash (I'm using Mathematica 10.0.1 Windows 64-bit):


A = SparseArray[{}, {3, 3}];
A[[1, {1, 1}]] += 1

This is just a minor modification of the following lines:


A = SparseArray[{}, {3, 3}];
A[[1, {1, 2}]] += 1


which are designed to increment entries {1,1} and {1,2} of A by one. I would have expected the crash-inducing example to increment the {1,1} entry by two. Instead, I get screams of death.


Any clues as to what is going on here?



This slight variation produces a more apparent crash in 7.0.1:


A = SparseArray[{}, {3, 3}];
A[[1, {1, 2, 3, 1, 1}]] += 1


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