Improve CPUAllocator OOM message

[dzhulgakov]

Spotted while debugging some problem

Before

>>> torch.empty(10**15)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: [enforce fail at CPUAllocator.cpp:56] posix_memalign(&data, gAlignment, nbytes) == 0. 12 vs 0

After

>>> torch.empty(10**15)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: [enforce fail at CPUAllocator.cpp:65] . DefaultCPUAllocator: can't allocate memory: you tried to allocate 4000000000000000 bytes. Error code 12 (Cannot allocate memory)

[facebook-github-bot]

@dzhulgakov has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[fmassa]

Wouldn't it be simpler for the user to print the amount in MB or GB?

[colesbury]

But how will users know now that they need to Buy new RAM? R.I.P. Samsung, SK Hynix, Micron

[facebook-github-bot]

@dzhulgakov merged this pull request in d9dcfac.