Use gcc 5.4 on xenial non-conda + use pytorch 0.4 official + fix broken python API

[prigoyal]

Fix docker image to use gcc 5.4 on xenial non-conda env to fix aten build which fails with avx related issues on gcc5.5. Ubuntu toolchain ships gcc 5.5 be default since April 24, 2018 hence not using the toolchain for gcc 5.4

issue filed on pytorch repo pytorch/pytorch#6992
i'll propagate this to gcc as well

partially helps #338

[ftynse]

Could you please add an empty line in your commit message between "Fix docker image to use gcc 5.4 on xenial non-conda env" and the rest? In git, the first "paragraph" (before the empty line) is the short summary and the rest is the longer commit message that are treated differently. We generally prefer short summaries to fit into 80 characters.

[ftynse]

SO this installs from PPA when asked for GCC 4.9, but what is the version shipped with the system?

[prigoyal]

system version 4.8.4

[ftynse]

then I don't really understand how is this supposed to make it use gcc-5.4 as the commit message says

[prigoyal]

for the trusty distrib, we use gcc4.9 but default shipped is 4.8.4
for xenial, we use gcc 5.4 but default shipped by ubuntu toolchain is 5.5 as of April 24

[ftynse]

so how do we get gcc 5.4 then? we only install from ppa if 4.9 is requested. so when 5.4 is requested -- nothing happens. I assume than the default 5.5 is used, which sort of contradicts your commit message.

[prigoyal]

if gcc version 4.9 is requested, we get it from ppa. otherwise, don't use the toolchain and apt install it. Earlier, gcc5 was coming from ppa as well which used to be gcc5.4 before April 24

[ftynse]

I guess the part that is missing from the description is that xenial has 5.4 by default

[prigoyal]

got it. I understand now what you mean. I'll edit the description. :)

[ftynse]

thanks! sorry it took so long

[skimo-openhub]

On Thu, Apr 26, 2018 at 03:13:33PM +0000, ftynse wrote: ftynse commented on this pull request. Could you please add an empty line in your commit message between "Fix docker image to use gcc 5.4 on xenial non-conda env" and the rest? In git, the first "paragraph" (before the empty line) is the short summary and the rest is the longer commit message that are treated differently. We generally prefer short summaries to fit into 80 characters.

Not just the one-line summary, but the entire commit message should fit in 80 characters. See https://github.com/facebookresearch/TensorComprehensions/blob/master/CodingConventions.md#commits skimo

[prigoyal]

thanks @ftynse for review, I just edited the description and also fixed the python API broken by a recent change. this PR should be good to go now and ready for review again :)

[prigoyal]

merging this to help facilitate fixing the Jenkins CI

@mingzhe09088 can you re-try the python tests again with this PR? I noticed the similar issue as you reported. It was broken in a recent change in PR 353.