[ubuntu] Ubuntu 16.04 randomly freezes when doing data analysis

Recently when doing data analysis, I started having issues with Ubuntu completely freezing: screen stops changing, mouse and keyboard do not respond, and hard drive light does not flash. I have tried waiting up to an hour for the system to unfreeze, but it doesn't and requires a manual reboot.

Looking into this issue, I have been able to reproduce the freezing by filling up the main memory and making the system use swap. For example, in R (with either the terminal or RStudio) I can use the following code to consistently freeze the system:

x <- replicate(1000000, 1:1000)

I first thought this may be an issue with R, so I ran the same code on Windows 10 (I dual boot on the same computer). On Windows, this code ran for a while, caused some unresponsiveness, and then gracefully stopped with an error:

> x <- replicate(1000000,1:1000)
Error: caot allocate vector of size 3.7 Gb
In addition: Waing messages:
1: In array(r, dim = d, dimnames = if (!(is.null(n1 <- names(x[[1L]])) &  :
  Reached total allocation of 8135Mb: see help(memory.size)
2: In array(r, dim = d, dimnames = if (!(is.null(n1 <- names(x[[1L]])) &  :
  Reached total allocation of 8135Mb: see help(memory.size)
3: In array(r, dim = d, dimnames = if (!(is.null(n1 <- names(x[[1L]])) &  :
  Reached total allocation of 8135Mb: see help(memory.size)
4: In array(r, dim = d, dimnames = if (!(is.null(n1 <- names(x[[1L]])) &  :
  Reached total allocation of 8135Mb: see help(memory.size)

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