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DanRRight · Posted: Wed Jun 15, 2022 10:29 pm Post subject: Fortran fashion designers

Remember i always told here that Fortran with time becomes only younger and will never go into oblivion? How cool way to say in Fortran DO-ENDDO for example ?

Old way:

mecej4 · Joined: 31 Oct 2006 Posts: 1897

DanRRight wrote: "Can anyone explain me how DO loop is working here?"

It is counting the number of links in a linked list.

More links to articles on linked lists in Fortran can be found at https://fortranwiki.org/fortran/show/Linked+list .

DanRRight · Posted: Wed Jun 15, 2022 11:55 pm Post subject:

Mecej4,
How step by step it is doing that? How it know to move to the next particle? How it knows how many particles are in the list to stop DO loop? Here is absent above object with all the rest definitions for head, next etc

DanRRight · Posted: Thu Jun 16, 2022 9:52 am Post subject:

Compiling this code with latest Intel Fortran takes 6-7 minutes on supercomputer. FTN95 on PC would do that in 6-7 seconds.

LitusSaxonicum · Posted: Sat Jun 18, 2022 5:00 pm Post subject:

Dan,

I'm pleased that you are still a fan of compiling with FTN95.

When I got a PC with a 486 and 16Gb RAM, I was able to run bigger problems than were possible on mainframes at 2 of the UK's leading Universities (I'll keep their names secret to save embarrassment). However, I didn't then expect the compilation to be faster, and as for execution, if the mainframe couldn't handle the problem, there was no way to compare.

Eddie

mecej4 · Joined: 31 Oct 2006 Posts: 1897

"When I got a PC with a 486 and 16Gb RAM,..."

Tall tales, Eddie. A 486 could not address 16 Gb. You had 16 Mb, may be?

I once had a 486 PC with 4 memory modules, each with 8 Mb of SDRAM.

LitusSaxonicum · Posted: Sun Jun 19, 2022 10:45 am Post subject:

Memory - human as well as computer - sometimes fails, after a long time. Of course it wasn't Gb, it was Mb - slip of the keyboard.

My 486 was the 66 clock multiplied version, and replaced a 386SX. I went to Dan computers around the back of the old Wembley stadium and bought the thing one Christmas Eve for cash. To get the 100 MHz AMD version, it needed a new motherboard in probably the hugest tower machine I ever had. The original probably had 4Mb RAM, and even then, one needed DBOS and/or some form of DOS extender that I can't remember now.

At that point, I was indulging in the sort of thing that Dan seems to do, which is a fervid change of computer with every new release of chip, probably involving a new motherboard, sometimes different (and bigger) hard drives and probably new and bigger memory sticks.

It was the last Intel machine I ever had, and I''ve used AMD ever since, and not only that, apart from laptops, I have built my own.

I always thought of those machines as 486s, but of course the AMD nomenclature was somewhat derivative of the x86 naming and rather different to Pentium, which is probably why I couldn't recall which one it was, lumping all of them into the 486 bucket. So the 16Mb probably wasn't on the real Intel 486DX2 but on an AMD equivalent.

I've had to have Intel chip laptops from time to time even though my preference is AMD. My old Uni only ever provided Intel machines for staff., usually the lowest spec they could get away with, reserving high powered machines for secretaries (who also got huge monitors) so that they could run WordPerfect nicely, whereas to run things like Finite Element software I had to work from home, a habit that served me well when I retired, and during the Covid lockdown!

I note that when I visit my former colleagues they are using supplied machines of decidedly inferior spec, but now that a couple of Gb (and yes, I do mean Gb this time) seems standard, and cpus are so much faster, it hardly seems to matter at all.

Thanks for the correction.

Eddie

DanRRight · Posted: Mon Jun 20, 2022 7:57 am Post subject:

Eddie,
When heavy work with the code development takes place i recompile hell amount of times per day. And when waiting for finish always one thing comes to mind: just lose 3 seconds per day and you will lose 3 working days ( 8 hours a day) over entire life. Waiting for compilation is pure 100% loss of time. And now imagine losing not 3 seconds but 3 minutes, 30 minutes total - hard to believe, but that's 180 days, 1800 days of waiting ;(

DanRRight · Posted: Mon Jul 04, 2022 8:45 am Post subject:

Try to feel my pain. On effing supercomputers you change one symbol and compilation even with MAKE utility (which only recompiles the file you just edited) still takes 1 min at least.