[LLVMdev] Google SOC - Fortran Front-End Application

[John T. Criswell]

Scott Fortmann-Roe wrote:
> Hi All,
>
> Thank you for all the excellent pieces of advice I got in response to
> the draft application I sent out.
>
> I have incorporated all (I think) of the suggestions into the
> application and it's much improved. Here is the updated version.
> Please don't force yourself to read through it again if you don't want
> to. I'll submit this version with any suggestions I receive on the
> 23rd.
>
> Thank you all,
> Scott
>
>
> ABSTRACT
> ----------------
>
> The purpose of this project is to develop a Fortran front-end to the
> Low Level Virtual Machine (LLVM) compiler infrastructure
> [http://llvm.org]. LLVM is a mature collection of tools that provides
> a powerful resource for language developers and end-user programmers.
> LLVM consists of roughly three components. The first is a front-end to
> a language (such as C, C++, or virtually any other) that parses the
> language and converts it into LLVM's Intermediate Representation (IR).
> The LLVM IR is a language- and target- independent representation. The
> second component of LLVM is a collection of powerful optimization
> routines that operate on the IR. The final module of LLVM is a backend
> that can compile optimized code to a number of platforms including x86
> and PowerPC, can emit an optimized C representation of the original
> program, or use a Just-In-Time compiler to interpret the program on a
> variety of platforms.
>
> To claim Fortran is mature is an understatement. In use for over 50
> years, Fortran is utilized in a wide variety of legacy code bases.
> While younger and flashier languages get all the press, Fortran still
> enjoys wide usage in many scientific fields and other
> businesses—especially when legacy code is involved. Additionally, the
> SPEC CPU2000 and CPU2006 suite of benchmarks, both of which contain
> Fortran components, are widely used as performance evaluation tools in
> both the research community and industry.
>
> The implementation of a Fortran front end would benefit both the
> Fortran user-base and the LLMV project. The scientific uses of
>   
s/LLMV/LLVM
:)

Also, to nitpick, I think FORTRAN is all capital letters.

> Fortran—along with its other applications—are often heavily involved
> simulations and calculations which are very resource demanding and
> could greatly benefit from LLVM's powerful optimization mechanisms.
> The LLVM project will, of course, benefit from having another
> front-end language and the resulting larger "market" available that
> can utilize LLVM. Additionally, the LLVM optimization team will have
> another case study to explore the effectiveness of its optimization
> routines. Especially the development of mixed-language optimization
> routines involving Fortran and one or more other language may be
> explored and implemented.
>
> Deliverables for this project are:
> * Fortran front-end to LLVM
> * Documentation and tools for using the front-end
> * A suite of tests to ensure the functionality of the front-end
>
> DETAILED DESCRIPTION
> ----------------------------
>
> The reader should refer to the abstract for a description of the goals
> of this project and their justifications. This section is devoted to
> the applicant's experience, interests, qualifications, and plan for
> completing the project.
>
> * Personal Background
>
> I am an Environmental Engineering and Economics double major at
> Swarthmore College class of 2008. My programming background is
> self-taught, and I have only had the available time to take a couple
> of formal Computer Science courses in my career. Most of my
> programming education has been driven by my passion for figuring
> things out and my willingness to hit my head against a problem until
> it is solved. My learning has been aided by the books of excellent Bay
> Area libraries, the kind support of community members of various
> projects, and the vast trove of resources available on the internet.
>
> My programming ideology is one of problem solving: I encounter a
> problem in my life and solve it using whatever tools or resources are
> needed to do so. To this end, I have dabbled in a wide range of fields
> from databases, to statistical analysis, to GUI applications, to web
> applications, and more. Examples of this work are an anti-censorship,
> in-browser web-browser [Palary Browser -- http://palary.org] and a
> unique calculator program for OS X [Longhand --
> http://longhand.palary.com]. I have also worked for a number of
> clients developing GUI applications, data analysis applications, and
> web applications.
>   
I'm not sure I have the best advice for convincing people, but I would 
recommend two changes:

1) I think you should talk about your strengths first and then talk 
about your weaknesses (if you need to talk about your weaknesses at 
all).  As written, you're giving them reasons to reject your application 
and then you try to talk them out of it.  I think you want to convince 
them first that you're capable of doing this project.

2) You may want to give a few more details about the projects you've 
done or are currently working on to give them a better insight into your 
skill.  I don't know what an anti-censorship, in-browser web browser is, 
and you don't specify what's special about your calculator program.  
Your application may be more impressive if, through a description of 
your projects, you indicate that you've written something difficult, 
innovative, or cool.

-- John T.
> I became interested in the area of language development as a result of
> a desire for better tools to deal with the environmental modeling and
> economical modeling issues that I came into contact with in my
> studies. It seemed to me as if these areas could benefit greatly from
> domain specific languages that were tailored to their specific needs
> (such as built in units in the environmental modeling case). I am
> currently working toward developing such a language for my Senior
> Thesis here at Swarthmore.
>
> * Motivation
>
> To gain the background to carry out the complicated task of developing
> a domain specific modeling language, I have since enrolled in an
> upper-level compiler course here at Swarthmore. Additionally, I have
> actively immersed myself in the field. In this immersion I came across
> the LLVM project and I believe that its IR would be an excellent
> target for the language I eventually create.  LLVM is a complex tool
> and I wish to gain much more familiarity with it so as to best utilize
> its strengths and capabilities.
>
> My primary motivation for working on a Fortran front-end for LLVM is
> gaining experience and background in language development. I want to
> learn from this experience, and would like to contribute to both the
> LLVM and Fortran community whilst doing so.
>
> * The Plan
>
> I will be able to spend roughly three-months this summer working on
> the front-end. I am not as familiar with the technologies involved as
> I would like to be, so my planning is necessarily imprecise. My rough
> plan proceeds as follows:
>
> =====
> - 2 weeks – Gain increased familiarity with the technologies: LLVM,
> Fortran, and GCC's Fortran implementation. Do not engage in any direct
> work on the project but acquire additional experience with the tools.
> Ascertain what previous work has been accomplished towards developing
> a Fortran front-end.
>
> - 4 weeks – Build the Fortran front-end; documenting the front-end as
> development proceeds.
>
> - 2 weeks – Smooth things out, unit tests, etc…
>
> - 1 week – Polish documentation, comments, and supporting documents.
> Ensure that the front-end can be maintained and worked on by other
> people.
>
> - 3 weeks – The three remaining weeks will be used to account for any
> unforeseen occurrences or inaccuracies in this plan.
> =====
>
> I plan on first attempting to implement the Fortran front-end by
> co-opting the GCC Fortran parser. I will most likely utilizethe GCC
> 4.2 Fortran front-end as earlier versions of the GCC Fortran front-end
> are less than ideal. Success in this approach has been demonstrated in
> other projects such as with the Ada LLVM front-end implemented by
> Duncan Sands. If this approach is successful, the version of Fortran
> that will be targeted is Fortran 95.
>
> If that fails, I will build a front-end using ANTLR [http://antlr.org]
> a parser generator with which I am familiar and for which a Fortran
> grammar is already available (targeting an obsolete version of ANTLR,
> but it should not be too difficult to update). Completing the
> front-end using ANTLR is a much larger task than using GCC. A
> front-end supporting a subset of a Fortran version will definitely be
> achievable, but it is unlikely that the entirety of the Fortran
> version will be completed in the available time. Fortunately, it is
> unlikely that I will have resort to this approach.
>
> * In Short
>
> I'm psyched :)
>
> I am thrilled to start working on this project, and feel that I will
> be able to complete it on time successfully. While working on this
> project, I hope to learn a great deal.
>
> * Acknowledgments
>
> I would like to thank Jeff Cohen, Kenneth Hoste, Chris Lattner, Scott
> Murray, Duncan Sands, and Bill Wendling for their advice and
> suggestions as to a fruitful course for this project.
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>