[Beowulf] Teaching Scientific Computation (looking for the perfect text)

Robert G. Brown rgb at phy.duke.edu
Tue Nov 20 17:38:30 EST 2007


On Tue, 20 Nov 2007, Nathan Moore wrote:

> RGB, Thanks for the references.  Oh btw, the link to the C projects seems
> broken.

Oops, looks like I overloaded the term "project" and overwrote it with a
later upload of the latex project template.  My bad.  I'll fix it and
repost, but probably not for a wee while yet, not today...

    rgb

>
> Nathan
>
> On Nov 20, 2007 2:23 PM, Robert G. Brown <rgb at phy.duke.edu> wrote:
>
>> On Tue, 20 Nov 2007, Nathan Moore wrote:
>>
>>> After reflection though, I've started to wonder about the wisdom of my
>>> choice.  Specifically (like RGB), I love the GSL library, and extending
>> GSL
>>> to fortran in an intro class is non-trivial.  Additionally, most vendors
>>> supply "fast" hardware libraries in C (I may be ignorant, but if a
>> student
>>> wants to call an AMD ACML fast-math function(
>>> http://developer.amd.com/acml.jsp), or write a linear algebra function
>> to
>>> run on a graphics card(http://developer.nvidia.com/object/cuda.html),
>> the
>>> vendors seem to assume that you'll write the code in C).
>>>
>>> Also, and more relevant, I assume that most employers word-associate
>>> "Fortran is to backwards as C is to competence".
>>>
>>> So, I'm thinking about reworking the class to favor C, and fearing 3
>> weeks
>>> of pointer and addressing hell.  For those of you who teach scientific
>>> computation (and also those of you who hire undergrads), I'd be grateful
>> for
>>> your thoughts.  One specific question I have is what text covers
>> scientific
>>> programming and touches on MPI using the C language.
>>
>> Ah, grasshopper, you have finally managed to snatch the stone.  (Or is it
>> drink the kool-ade, I never can remember...;-)
>>
>> Let's see.  There are some truly excellent books that have helped my
>> independent study students on programming (most of whom are trained in
>> Java only these days, God help us all:-( learn C.  There are also two
>> free online C reference manuals, three if you count Gnu's (which
>> unfortunately is by far the worst of them).  I will endeavor to provide
>> you with a short shopping list, as I keep pretty much a complete C
>> programmer's reference toolkit on my laptop at all times including the
>> two aforementioned C textbook/manuals, various other free/online
>> manuals, and of course the man pages.  Even though I write a LOT of C I
>> still have to look things up -- what programmer doesn't?  When I'm
>> online I have even more access to free resources as GIYF.
>>
>> To my mind, the most difficult aspect of programming in linux for a
>> newbie isn't the compiler, it is the programming environment and
>> learning how to create a project directory, put it under subversion (or
>> possibly CVS) control, pick a text editor (not a WYSIWYG WP, an editor,
>> ideally one that groks compilation and make), and write that first hello
>> world program.  The second longest thing is teaching them a sane way of
>> getting variables off of the command line and into a program, especially
>> when some of the kids have never really used a command line at all in
>> the past.  Drop the mice, guys -- fingers on those home keys!  That's
>> where you type, after all...
>>
>> This process is greatly sped up if you provide them with a "standard
>> program template" like the one here:
>>
>>   http://www.phy.duke.edu/~rgb/General/project.php<http://www.phy.duke.edu/%7Ergb/General/project.php>
>>
>> which can create a work directory for you by running a little script and
>> prepopulate it with a functional Makefile and a set of hello-world
>> sources complete with a routine that parses the command line and can
>> fairly easily be hacked to add new CL arguments.  Note that this
>> template is always changing and you'll like have to modify it and test
>> it to meet the needs of your students, but it will TREMENDOUSLY improve
>> your ability to grade projects as they can "make tgz" and ship you a
>> project tarball, ready to unpack, build, test.
>>
>> I personally like the jove (Jonathan's Own Version of Emacs) for all
>> text editing because emacs is maddeningly complex, crufted, overladen
>> with features, and hence all but unlearnable.  jove installs easy, there
>> is a teachjove tutorial that will walk students through all they need to
>> know to use jove as a semi-IDE, and you're done.  I've got jove
>> tarball/rpm's, or it is in debian ready to roll from what I've heard
>> (what isn't?:-).
>>
>> One of the two C books I'd recommend is here:
>>
>>   http://www.phy.duke.edu/~rgb/General/c_book.php<http://www.phy.duke.edu/%7Ergb/General/c_book.php>
>>
>> which is a legal mirror of the original book.  Note well the license is
>> a "beer" license.  You have to buy the authors beer if the opportunity
>> to do so presents itself.  This may present problems for your students
>> if they are underage, but I imagine the authors of the book will be down
>> with that.  So each student can mirror my mirror, or they can find the
>> original online with google or otherwise and mirror that.  That way they
>> can have an entire, quite readable book on C, replete with cut-n-paste
>> examples, free, installed on their personal computers where it is always
>> handy and useful.
>>
>> This is a "beginner" level book -- complete enough for simple code, but
>> not really up to snuff on things like threads or advanced data
>> structures.  For the SERIOUS student, or the student working on an
>> advanced project where forking, threads, and so on are necessary, I'd
>> recommend that they use Dave Marshall's book:
>>
>>   http://www.cs.cf.ac.uk/Dave/C/CE.html
>>
>> This is a GREAT book.  A full out, pro-grade book on C including some
>> very advanced stuff.  Parts are a tiny bit dated -- the first chapter of
>> the book deals with CDE on Solaris -- but it is a killer reference.
>> Online access is free, and if you contact Dave regarding redistribution
>> of the book to a class full of students in PDF format (which he has, and
>> for that matter so do I) he might be open to it.  He sent one to me
>> willingly enough when I asked him about it, so I've got it on my laptop
>> for eternity, network or not.  He was going to look into a Gnu OPL for
>> it when last we communicated.  At this point I'd suggest (to him)
>> throwing it up onto Lulu for cheap download in PDF or paper print with a
>> reasonable markup -- he'd make money and students would get a generally
>> lovely book in whatever form(s) they prefer.
>>
>> Then there are a variety of algorithm books or programming environment
>> books I like to recommend to students I'm teaching:
>>
>>  * King Abel and Graham Glass's book.
>>
>> http://www.amazon.com/Linux-Programmers-Users-Graham-Glass/dp/0131857487
>>
>> I've used this book since it was just glass and Unix instead of Linux.
>> A classic.  Way too EXPENSIVE a classic at $84, but a classic.
>>
>>  * Mastering Algorithms in C (O'Reilly Seahorse IIRC).  Excellent
>> reference for stock-in-trade stuff like data structures, linked lists,
>> sorting, numerical methods (to a point).
>>
>>  * Kernighan and Pike's The Practice of Programming.  I'd actually make
>> this a requirement for any new C programmer.  It covers things like
>> INDENT YOUR GODDAMN CODE AND I REALLY MEAN IT, and IF YOU DON'T COMMENT
>> YOUR CODE YOU WON'T UNDERSTAND IT YOURSELF TWO WEEKS FROM NOW, and WHAT
>> THE HELL IS aRp IN YOUR CODE?  DOES THAT MEAN SOMETHING TO YOU ASIDE
>> BESIDES "BARF"?  so that you don't have to yell QUITE so much at your
>> students and has lots of other wisdom as well.
>>
>>  * Optionally Kernighan and Pike's The Unix Programming Environment
>> isn't quite as good as Abel and Glass, but it is still damn good and and
>> excellent reference.
>>
>> For numerical methods per se, well, there is STILL Numerical Recipes in
>> C, but I no longer use it in any code because it sucks in so many ways.
>> It is encumbered, with a code-reuse license out of the dark ages, I mean
>> a really, really, really bad one (in spite of the fact that some of the
>> code they are trying to encumber comes right out of the literature).  I
>> personally think that all they need is the GSL itself and the GSL's
>> manual, online or otherwise.  At this point anything you're at all
>> likely to have beginners doing is well-supported there, with
>> documentation and code examples, with a list to ask difficult questions
>> on.  And yes, they can buy a paper copy of this from Amazon (and help
>> support the project at the same time).  And it is even cheap.
>>
>> My actual favorite numerical methods book is alas in fortran --
>> Forsythe, Malcom and Moler -- but all that they really need from any
>> such textbook is a two lecture discussion on discretization error and
>> bad ways of doing what appear to be straightforward tasks because
>> computers do discrete arithmetic.  If the course were going to FOCUS on
>> numerical methods, e.g. derive a 4th-5th order RK ODE solver and code
>> it, you'd likely need t textbook to help, but to USE an RK ODE solver --
>> just the GSL, just the GSL.
>>
>> The last reference I like to recommend is (of course) Knuth's TAOP.
>> 'Nuff said.  Expensive as hell for the full set, but it IS the only
>> reference you'll ever need, unless you plan to do network programming in
>> which case you'll likely need one or more of Stevens' excellent books,
>> or plan to do systems programming at the kernel level, in which case
>> you'll need several books I'm not going to list here, or MPI or PVM, in
>> which case you'll need -- what?  Well there are a few excellent books
>> from IIRC MIT press on them, but they may be dated at this point.  There
>> are the many superb articles on www.clustermonkey.new and in the Linux
>> Magazine archives.  Again, having a good template goes a long way --
>> there is a PVM template on my website but I don't use MPI (or PVM, much,
>> anymore) so you'll have to get them from other folks.
>>
>> I've found that some subset of the *'d references and free references
>> above can take a student that can program in ANY language already and
>> make a credible C programmer out of them in a semester.
>>
>> And jeeze, man.  Pointers rock.  If you want students to actually learn
>> how computers work so that they can UNDERSTAND what they are doing they
>> are peerless (if painful) instruments of learning.  Want a block of
>> memory?  Go get it, lay it out, access it, all with fairly high level
>> commands.  Want to overlay a secondary addressing scheme on top of it?
>> Sure, why not.  Allocate a vector, pack its addressing into a ***pointer
>> to make a matrix[][][] that you can still pass to an ODE solver that
>> wants vectors only, while addressing it in a completely natural way in
>> the deriv evaluator.  You can do things in C easily that you can't do AT
>> ALL in other languages, all because of pointers and the ability to
>> recast variables.  Sure, you can break a program more horribly than you
>> ever could in Fortran (although I've managed to break fortran pretty
>> horribly).  That's why you get them K&P and make them read it FIRST, and
>> why you teach them about adding
>>
>>
>> #define MYDEBUG(b)  if ( (verbose == b) || (verbose == D_ALL) )
>>
>>  typedef enum {
>>    D_QUIET,
>>    D_ALL,
>>    D_V_2,
>>    D_V_3,
>>    D_V_3,
>>    N_DEBUG };
>>
>> into their primary program header and sticking:
>>
>> x = 1.0;
>> MYDEBUG(D_V_1){
>>  fprintf(stderr,"# This is my subroutine 1, and variable x = %f\n",x);
>> }
>>
>> chunklets all over their damn code as they write it.  Run the program as
>>
>>   $myprog -v 2
>>
>> and out spews:
>>
>> # This is my subroutine 1, and variable x = 1.000000
>>
>> Run it as
>>
>>   $myprog
>>
>> and it doesn't.  I instrument my code so that at any instant I can get a
>> completely verbose picture of everything it is doing as it goes along,
>> or "zoom in" on just one subroutine.  It is tricks like this that make C
>> programming robust and doable.  One should do it in any language, of
>> course, but in C it is ESSENTIAL to make sure that the program is doing
>> what it is supposed to be doing, not overwriting array boundaries, and
>> so on.  In fortran you are lulled into a false sense of security because
>> you THINK the compiler or runtime engine will catch errors for you when
>> in fact there are lots of errors they will miss, and then you are REALLY
>> dead.
>>
>> HTH,
>>
>>    rgb
>>
>>> regards,
>>>
>>> Nathan Moore
>>>
>>>
>>>
>>
>> --
>> Robert G. Brown
>> Duke University Dept. of Physics, Box 90305
>> Durham, N.C. 27708-0305
>> Phone(cell): 1-919-280-8443
>> Web: http://www.phy.duke.edu/~rgb <http://www.phy.duke.edu/%7Ergb>
>> Lulu Bookstore: http://stores.lulu.com/store.php?fAcctID=877977
>>
>
>
>
>

-- 
Robert G. Brown
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone(cell): 1-919-280-8443
Web: http://www.phy.duke.edu/~rgb
Lulu Bookstore: http://stores.lulu.com/store.php?fAcctID=877977
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