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"Team Ada: Ada Advocacy Issues (83 & 95)" <[log in to unmask]>
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Wesley Groleau <[log in to unmask]>
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Fri, 5 Feb 1999 09:37:49 -0500
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Here's another request for assistance in a battle that looks like it's already
lost.  I unfortunately don't have the time to adequately answer all of the
misleading (a few are downright false) claims here.  Anyone is welcome to throw
in response to specific items.  Please, though, let's not have several reposts
of the entire presentation just to answer one line.  Of particular value are
quantified empirical evidence.

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Programming Language Trade Study

Introduction/Scope



? Programming language trade study for the _________ ? Addresses the ______ (MAS) and _________ only ? _________ has already determined that they will be using C ? Current candidates are ? Ada 83 ? Ada 95 ? C ? C++ ? A separate study will be performed for _________ Approach/Methodology ? Identify assumptions and relevant data to ______ ? Contrast and compare candidate language features ? Survey existing generic language comparative studies ? Review earlier MAS language selection study ? Assess how well each language supports concurrent, real-time object oriented development Examine candidate language strengths and weaknesses and the ability to provide mitigation of each in comparison to other candidates. ? Examine current industry trends particularly in reference to future supportability ? Catalog and examine local and company wide experience ? Examine staffing considerations, immediate and future ? Choose candidate which has the lowest residual risk Assumptions and Relevant Data to ____ ? The ______ Processor is currently a HP V2500 Convex running HP/UX 11.0 ? _______ software will be done in C ? ________ will be done in C++ ? There is limited potential for legacy software reuse ? _________ are JOVIAL and Assembly ? translators do not account for language optimization, modern computing architecture or DIICOE ? embedded RTOS specifics ? _____ is Ada 83, functional decomposition ? moving baseline and different mission makes mapping/reuse difficult ? _____ to be redesigned using object oriented ? methodology to minimize impact of volatile requirements ? Software costing model sensitivities show that language selection has little impact on cost ? domain experience (18% improvement) ? overall engineering competency (analysts: 29% improvement, programmers: 30% improvement) ? programming language (5% improvement). ? Legacy _______ systems include: ? ______: FORTRAN on a Cyber ? _____ , ______ & ______: JOVIAL on a Cyber running RTOS ? _____: Ada 83 on a VAX running VMS ? ______, et al: Ada 83 on a HP running Unix ? Programming language vendor base ? Ada 95 (Rational, Green Hills, GNAT, Aonix) $230 million in sales ? flat sales last year ? C/C++ $16 billion in sales, a factor of 70 greater than Ada ? increasing sales last year And Then There Were Two ? Candidate languages reduced to Ada 95 and C++ ? Ada 83 and C eliminated during preliminary analysis ? Neither are Object Oriented ? Vendor tool support for Ada 83 is being phased out in favor of Ada 95 Survey Existing Generic Language Comparative Studies ? A web search revealed few comparisons which included Ada ? The majority of the comparisons concentrated on commercial languages such as C/C++, Java, Smalltalk, Perl, etc. One Ada 95 vs. C++ comparison found was the book "Guidelines for Choosing a Computer Language", P.K. Lawlis (C.J. Kemp Systems, Inc.), 2nd Edition, August 1997 ? Recommended Ada 95 due to superior language features "Guidelines for Choosing a Computer Language" with Regard to _____ ? The criteria and ratings established by P. K. Lawlis are somewhat subjective. With a different viewpoint, values may be reassigned and criteria modified so as  to result in a different language selection. ? address the language domain only and are independent of operating system capabilities e.g. Under "Concurrency Support", Ada 95 was assigned a rating of eight while C++ was assigned a zero. Concurrency in C++ is provided by the OS. - do not take into consideration good rigid software standards practices. We  programmatically tailor via design and coding standards to limit a language's weaknesses and maximize its strengths. Performed in C++ successfully on Raytheon's Personal Rapid Transit (PRT) Program. ? do not address future supportability issues In P. K. Lawlis' Own Words ? From "Is the Answer Always Ada?", Patricia K. Lawlis, Proceedings: Tri-Ada 97 Conference "When software engineering considerations are factored into the process, a clearer picture of what is really important in a language choice emerges." "Ada will rate highly only if it continues to have good support from both vendors and the educational community and, indeed, only if that support continues to grow." Ada and C++ Language Feature Comparison General Assessment of Language Features ? Either Ada 95 or C++ can successfully be used to implement ______ ? Ada 95 successfully used on: ? ______, _______ ? C++ successfully used on: ? ____ (safety critical embedded program) ? _____, _______ ? more significant usage of C++ at _____, ______ and _______ locations Generally, technical discriminators between the languages are minor, and there are no areas that a strength in one does not have a work-around in the other (discussed further in Advantages/Disadvantages section). Ada 95 Advantages ? Potential of 6-15% of _______ contributing s/w implemented in Ada 83 ? There exists a pool of in-house programmers experienced in writing real-time radar software in Ada ? ______, _______, _______ ? Superior run-time constraint/range checking ? Superior exception handling ? Tends to lessen the capability to "hack" code due to the formalism of the language Ada 95 Disadvantages ? Long term future and supportability is questionable ? Ada mandate has been rescinded ? Ada Joint Program Office is no longer funded by the government ? Vendor pool is limited and shrinking ? Ada tool sets tend to lag behind C/C++ releases ? Ada tool sets tend to be more expensive ? Diminishing university base and future availability of Ada trained entry level  engineers. Because of the marketability of other commercial languages (e. g. C++, Java) there is a strong motivation for experienced Ada trained engineers to gain experience with these languages rather than to continue gaining experience in Ada 95 Ada 95 Disadvantages (continued) ? Performance concerns ? compiler efficiency ? most vendors put emphasis on optimizing C++ compiler first due to greater industry competition ? run-time constraint/range checking ? when not disabled, performance overhead is added by the compiler ? RTE overhead ? additional layer between application and native OS ? Tends to hinder implementation of fast prototypes due to the formalism of the language ? Availability of compilers and development tools on next generation CPUs in question C++ Advantages ? C++ Advantages ? Much better long term supportability position ? Broader university and vendor/tools support on virtually every platform ? Long term availability of trained engineers ? C/C++ has native compilers and libraries on the HP UX system ? Opportunity for single development tool set since signal processing software is to be done in C Many expect desirable Ada 95 features to migrate into the C++ standards over the  next few years, and already has in the cases of ? Overloading of operators ? Ada generics (became C++ templates) ? Exception handling C++ Disadvantages ? C++ Disadvantages ? No legacy software for ______ is written in C/C++ ? offset by higher corporate metric for productivity (approx. 20%) ? Fewer C++ hard real-time programs implemented at Raytheon ? Run-time constraint/range checking must be implemented by the programmer ? Exception handling exists, but is inferior to Ada's ? Tends to allow "hacking" due to the availability of true pointers (C) versus Ada access types (C++ references) Can Ada overcome its disadvantages? ? Ada has a much narrower and shrinking vendor base and talent pool than C++ ? Staff ______ with Ada trained personnel and offer Ada training to non-Ada trained professionals and new hires ? Work with the Ada vendors to deal with long term supportability issues ? Can Ada overcome its disadvantages? (continued) ? Ada has worse performance than C++ Debated and implementation specific, however, many performance issues are design  based and can be avoided through coding standards Ada vendor resources are limited, and so Ada compilers are not getting the same amount of energy as is being applied to improving C/C++ compiler code generation  performance, etc. ? Those features that are performance prohibitive need not be used (true in either language). Ada offenders include: ? Protected sections ? Exception handling recovery Can C++ overcome its disadvantages? ? C++ has a smaller pool of individuals within Raytheon with real-time radar software experience than Ada. ? Real-time C/C++ experience does exist in ______ in the ________ area ? _________, portions of ______ (other portions were Ada 95), _______, _______, ____, _____ ? Domain knowledge and engineering skills dominates ? Language has a minimal effect in software costing models ? Most programmers know 5-6 languages, and they certainly can learn another and have a strong motivation to learn C++ Can C++ overcome its disadvantages? (continued) ? C++ has inferior runtime constraint/range checking ? User-supplied checks may prove more efficient (being put only where they make sense), but require greater thought ? May be placed as conditional compiles ? May be in runtime portion or in classes ? C++ has inferior exception handling (s/w and h/w) Legacy systems do not use Ada's exception handling for fault tolerance due to performance impacts and domain requirements; hence, this superior potential has never been utilized. Therefore C/C++ throw/catch ability is sufficient

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