TweetFollow Us on Twitter

Running NAG F95 on a Mac

Volume Number: 20 (2004)
Issue Number: 6
Column Tag: Programming

Running NAG F95 on a Mac

by Peter Amerl

Was Newton's Apple a Macintosh?

The Measurement Scales Uncovered

With OS X, Apple unleashed a new tool upon the computing community that even Sir Isaac Newton would have been proud to use. Who knows, maybe he would have belonged to those in scientific computing who prefer to use the Unix command line interface, and the X windows interface. Or, maybe he would have liked the slick Mac interface, and its newly found flexibility. Either way, most scientific programmers whom I know (including myself) tend to use the command line interface since their input and output data are weighed in hundreds of mega bytes, and the code often massages and stores the reduced data, thus requiring only a very basic interface. Furthermore, coding for those in science is a means to an end (fame and fortune). Often it is necessary for scientific code to be portable, permitting development on the Mac while enabling compilation on the latest Teraflop Cray, or super cluster. This leads to my criteria for the evaluation of the NAG compiler:

  • A streamlined coding environment

  • a good syntax checker

  • an intuitive and easy to use debugger

  • compiler optimization options

  • options to enforce standards compliance

The bulk of scientific computing is performed using two languages: C, and Fortran. Although C has evolved over the past decades with many new scientific libraries, abstraction layers in C++ simplifying the coding process, it is not always the best choice for scientific computing. Many solved computational problems are available on web sites such as http://www.netlib.org. A good fraction of these routines are coded using one of the Fortran flavors. Consequently, the language is likely to remain a scientific favorite for some time. The selection of third party Fortran compilers available for OS X is quite limited, and unfortunately, a good open source compiler for F90 or F95 is not available to date. Current third party contenders such as NAG F95, IBM XL Fortran, and Absoft ProFortran support compilation of source code for the F77, F90, and F95 standards. This review will discuss the NAG compiler for Mac OS X.

Experiences with the NAG Fortran 95 Compiler

The Nag F95 compiler has a multitude of features, such as automatic file preconnection, IEEE 754 support, automatic garbage collection, memory tracing, undefined variable detection, a random number generator that is seeded based on the time of day, etc.. Yet this is all material that can be obtained from the usual propaganda sheets. Once I had the NAG compiler installed and functioning, the fun started. The compiler options are just what one would expect from a Un*x style Fortran compiler. The following options set it apart from other compilers. It can provide compilation feedback that is color-coded, so that compiler warnings, errors, and informational messages are displayed using different colors. This makes it easier to scan the resulting output for compilation problems. Support for conformance checking is included, although apparently only for the Fortran 95 standard. This conformance checking can be performed in the following ways: the compiler can provide warning messages on the use of extensions to Fortran, syntax that was deleted in the transition to F95, and obsolete syntax and commands. One superb feature that NAG provides with its Fortran compilers is runtime garbage collection that can be enabled with "-gc" during the link phase. In the past, the automatic garbage collection has saved me valuable system resources when a routine repetitively needed to allocate and deallocate a number of large dynamic arrays.

The compiler also accepts, and checks HPF directives, but unfortunately does not compile them into the executable. Through the lack of AltiVec (a.k.a. Velocity Engine) library support, it is clear that NAG created the compiler to serve as a general-purpose, platform independent tool. Mac G4 and G5 users must create wrapper functions in C++ to take advantage of the AltiVec routines, a situation that is less than ideal for those looking for Velocity Engine performance improvements. On the other hand, the lack of these additional functions makes the NAG compiler a good (foolproof) compiler to use for porting code to other platforms. An integrated development environment is not provided with the compiler, further gearing the compiler to command-line or emacs jocks (such as myself). At the time of this writing, the compiler was not designed to work with Xcode. This omission may not be a serious stumbling block as NAG does supply its own graphical debugger, upsf95, derived from the open source ups debugger. Information about it can be found at http://ups.sourceforge.net. I found the debugger to work much like graphical implementations of gdbg. For people with dual processor systems, a more serious omission is the lack of parallel processing support.

I suspect that the NAG compiler is still showing some teething pains. Upon installing the compiler on two systems, a dual G5 running Panther and a G3 running Jaguar, I immediately ran into trouble. On the G5, the compiler could not compile a "Hello World" program. Using the "ieee=full" compilation flag changed the executable favorably, but did not entirely fix the problem. In all fairness, I later found that the error occurred every time I compiled as the OEM user after allowing the system to go to sleep. On the G3 with OS X 10.2.8, the code would not compile under the OEM user. Magically, the problems disappeared when I created a non-administrative user account to compile and execute programs. It is possible the problems were caused by other software packages installed on both computers. After the initial frustration, the compiler ran smoothly. I could even compile and execute about 13000 lines of scientific Fortran 90 code originally destined for the SGI platform without problems.

The Bottom Line

Pros:

The compiler functioned well once its quirks were resolved. To me, the debugger felt much like a graphical version of "gdb" and was very usable. The compiler optimized the code noticeably well considering its lack of AltiVec support. The color-coded compilation messages are an excellent touch, and of great benefit to command line compilation. Most important to me, the garbage collection, and cross-platform compatibility functioned superbly.

Cons:

The lack of an IDE or Xcode compatibility forces the user to rely on other editors. Also missing is the ability to compile code for parallel processing. It appears that on some systems, the compiler can potentially act somewhat capriciously. Fortunately, using a non-administrative account with no additional software or haxies installed fixed code generation problems for me.

Recommendations

For anyone who has a favorite editor, and prefers to use make files, this compiler will be worthwhile. If Xcode integration is desired, the NAG F95 compiler is not the tool to use. Perhaps, with properly placed suggestions from users, NAG will support Xcode development in a future release. If you are looking for cross platform compatibility you will most likely also be well served. Before using the compiler I suggest the creating a clean user account. Once this is accomplished, run the compiler from within that account. In any case, this is an excellent practice for computer security.

In Closing

Regardless of the compiler and operating system, the Apple Macintosh would not have been suitable for Sir Isaac Newton. It would likely have rendered him unconscious, or worse, as it fell on his head. Who knows, we might not know about gravity, or calculus, without Newton's contributions. Although most students would be much happier without these, it would also make present day computers unlikely.


Peter Amerl is a PhD physicist who has been coding scientific data reduction routines, and charged particle trajectory simulations for scientific instruments using Fortran 90 and 95 since 1996. Peter started his computing experience in 1982 with the Apple II+, eventually graduating to the Mac+. For a time of about seven years, he turned to the dark side until 1994, when the stability of Linux caught his eye. This fairytale continued until a wondrous discovery - OS X. Now Peter happily codes scientific routines on a G5.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Latest Forum Discussions

See All

Combo Quest (Games)
Combo Quest 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: Combo Quest is an epic, time tap role-playing adventure. In this unique masterpiece, you are a knight on a heroic quest to retrieve... | Read more »
Hero Emblems (Games)
Hero Emblems 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: ** 25% OFF for a limited time to celebrate the release ** ** Note for iPhone 6 user: If it doesn't run fullscreen on your device... | Read more »
Puzzle Blitz (Games)
Puzzle Blitz 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Puzzle Blitz is a frantic puzzle solving race against the clock! Solve as many puzzles as you can, before time runs out! You have... | Read more »
Sky Patrol (Games)
Sky Patrol 1.0.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.1 (iTunes) Description: 'Strategic Twist On The Classic Shooter Genre' - Indie Game Mag... | Read more »
The Princess Bride - The Official Game...
The Princess Bride - The Official Game 1.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: An epic game based on the beloved classic movie? Inconceivable! Play the world of The Princess Bride... | Read more »
Frozen Synapse (Games)
Frozen Synapse 1.0 Device: iOS iPhone Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Frozen Synapse is a multi-award-winning tactical game. (Full cross-play with desktop and tablet versions) 9/10 Edge 9/10 Eurogamer... | Read more »
Space Marshals (Games)
Space Marshals 1.0.1 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.1 (iTunes) Description: ### IMPORTANT ### Please note that iPhone 4 is not supported. Space Marshals is a Sci-fi Wild West adventure taking place... | Read more »
Battle Slimes (Games)
Battle Slimes 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: BATTLE SLIMES is a fun local multiplayer game. Control speedy & bouncy slime blobs as you compete with friends and family.... | Read more »
Spectrum - 3D Avenue (Games)
Spectrum - 3D Avenue 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: "Spectrum is a pretty cool take on twitchy/reaction-based gameplay with enough complexity and style to stand out from the... | Read more »
Drop Wizard (Games)
Drop Wizard 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Bring back the joy of arcade games! Drop Wizard is an action arcade game where you play as Teo, a wizard on a quest to save his... | Read more »

Price Scanner via MacPrices.net

Apple’s M4 Mac minis on sale for record-low p...
B&H Photo has M4 and M4 Pro Mac minis in stock and on sale right now for up to $150 off Apple’s MSRP, each including free 1-2 day shipping to most US addresses. Prices start at only $469: – M4... Read more
Deal Alert! Mac Studio with M4 Max CPU on sal...
B&H Photo has the standard-configuration Mac Studio model with Apple’s M4 Max CPU in stock today and on sale for $300 off MSRP, now $1699 (10-Core CPU and 32GB RAM/512GB SSD). B&H also... Read more

Jobs Board

All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.