Tuesday, April 10, 2018

BlueSkiesResearch.org.uk: EGU 2018 Day 1

Going to try a mini-blog straight away to avoid a big backlog. Arriving late on Sunday to a self-catering apartment meant a quick shop on Monday morning and missed session. As I said to Didier when he complained that I missed his 8:30 session (with a sceptic talk first up), I had something else more important already scheduled – breakfast! There was a brief moment of excitement later on when I asked a hostile question and the speaker accused me of being Jonty Rougier. No, he’s the other one who does that 🙂 The presentation in question was something that basically reproduced our results from several years ago, only less completely and correctly. Well, that’s my side of the story anyway. I presume Jonty has yet another side. To be honest we agree far more than we disagree but of course it’s the disagreements that make it fun.

Main event of the day – apart from me blagging my way into a free lunch –

IMG_4357
TISATAAFL!

– was the GMD 10th anniversary celebrations. A mixed session of short talks and a reception at the end of the day. When we set it up 10 years ago I never really imagined it would be so successful. So that’s really been (and continues to be) a lot of fun. Rolf Sander had a small puzzle that computing experts might like to consider: firstly, what does this Fortran 77 code output, and secondly, why? I answered the first part easily enough, the second was more challenging.

This is the code:

 Screenshot 2018-04-09 21.48.20

which can be found here if you want to download it and try it yourself. I should however warn you that some have found it either does not compile or does not generate the correct result depending on compiler. But I have it on (reasonably) good authority that it is acceptable code that should work (though not necessarily how you would expect…) according to the formal standard.

Here are our merry band of intrepid executive editors. Well, the 4 of them (out of 6) who could attend. One of them is jules and three of them are not. They all have feet really, just imagine 8 open-toed sandals and you won’t be far wrong.

IMG_4363

And so to bed. Jules has a 7:30 meeting to look forward to. I have breakfast again 🙂

10 comments:

William Connolley said...

OK, that is a nice puzzle and it took me a while. It produces the "right" answer with f77 (gcc version 3.4.6 20060404 (Red Hat 3.4.6-19.el6)), FWIW. And I've now fully understood the second part. Argh.

James Annan said...

Congratulations! I thought you would be a good bet for getting it right. If you want a garish orange t-shirt, there may still be a prize available (email rolf directly).

William Connolley said...

Gosh, is it considered that hard? I shall feel pleased with myself, though I did take an hour and several compilations with debug prints (which bizarrely (ha!)) changed the answer) before finally grokking it in its fullness.

jules said...

Well, most are not compiling it, just trying to do it analytically. In fact it seems to not produce the right result on all compilers - but that always was the problem with Fortran 77.

Only one person at the reception remarked that Fortran 77 was a bit after their time! :-)

James Annan said...

...and that was jules' Dad!

Phil Hays said...

OK, I think I got it. Both parts.
Fortran 77 was after my time as a Fortran programmer. I haven't touched Fortran since 1975. After this... I hope to never touch Fortran again.

Remembering nighttime sessions punching cards helped me a lot on the second puzzle. If you ever punched cards for a program, this is a huge hint.

"gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)"

James Annan said...

Both?

jules said...

Wasn't!
Was someone at least a generation younger.

James Annan said...

Oh yes your Dad had forgotten what fortran was :-)

Phil Hays said...

Two harder reasons why the answer isn't quite what might be expected. One very easy reason.
Vagrtre glcr pnfg
pbagvahr punenpgre
VS (K .YG. 60.) GURA TNEONTR K = K + 7.
CEVAG *,'ERFHYG=',K
RAQ VS
(ROT13)