Engineering topics

Chan, Gordon C.

Publications and source records attributed to Chan, Gordon C..

4 records

NASA NTRS1992

NASTRAN internal improvements for 1992 release

The 1992 NASTRAN release incorporates a number of improvements transparent to users. The NASTRAN executable was made smaller by 70 pct. for the RISC base Unix machines by linking NASTRAN into a single program, freeing some 33 megabytes of system disc space that can be used by NASTRAN for solving larger problems. Some basic matrix operations, such as forward-backward substitution (FBS), multiply-add (MPYAD), matrix transpose, and fast eigensolution extraction routine (FEER), have been made more efficient by including new methods, new logic, new I/O techniques, and, in some cases, new subroutines. Some of the improvements provide ground work ready for system vectorization. These are finite element basic operations, and are used repeatedly in a finite element program such as NASTRAN. Any improvements on these basic operations can be translated into substantial cost and cpu time savings. NASTRAN is also discussed in various computer platforms.

Chan, Gordon C.↗

NASA NTRS1991

Improved NASTRAN plotting

The new 1991 COSMIC/NASTRAN version, compatible with the older versions, tries to remove some old constraints and make it easier to extract information from the plot file. It also includes some useful improvements and new enhancements. New features available in the 1991 version are described. They include a new PLT1 tape with simplified ASCII plot commands and short records, combined hidden and shrunk plot, an x-y-z coordinate system on all structural plots, element offset plot, improved character size control, improved FIND and NOFIND logic, a new NASPLOT post-prosessor to perform screen plotting or generate PostScript files, and a BASIC/NASTPLOT program for PC.

Chan, Gordon C.↗

NASA NTRS1990

NASTRAN migration to UNIX

COSMIC/NASTRAN, as it is supported and maintained by COSMIC, runs on four main-frame computers - CDC, VAX, IBM and UNIVAC. COSMIC/NASTRAN on other computers, such as CRAY, AMDAHL, PRIME, CONVEX, etc., is available commercially from a number of third party organizations. All these computers, with their own one-of-a-kind operating systems, make NASTRAN machine dependent. The job control language (JCL), the file management, and the program execution procedure of these computers are vastly different, although 95 percent of NASTRAN source code was written in standard ANSI FORTRAN 77. The advantage of the UNIX operating system is that it has no machine boundary. UNIX is becoming widely used in many workstations, mini's, super-PC's, and even some main-frame computers. NASTRAN for the UNIX operating system is definitely the way to go in the future, and makes NASTRAN available to a host of computers, big and small. Since 1985, many NASTRAN improvements and enhancements were made to conform to the ANSI FORTRAN 77 standards. A major UNIX migration effort was incorporated into COSMIC NASTRAN 1990 release. As a pioneer work for the UNIX environment, a version of COSMIC 89 NASTRAN was officially released in October 1989 for DEC ULTRIX VAXstation 3100 (with VMS extensions). A COSMIC 90 NASTRAN version for DEC ULTRIX DECstation 3100 (with RISC) is planned for April 1990 release. Both workstations are UNIX based computers. The COSMIC 90 NASTRAN will be made available on a TK50 tape for the DEC ULTRIX workstations. Previously in 1988, an 88 NASTRAN version was tested successfully on a SiliconGraphics workstation.

Chan, Gordon C.↗

NASA NTRS1989

Improved performance in NASTRAN (R)

Three areas of improvement in COSMIC/NASTRAN, 1989 release, were incorporated recently that make the analysis program run faster on large problems. Actual log files and actual timings on a few test samples that were run on IBM, CDC, VAX, and CRAY computers were compiled. The speed improvement is proportional to the problem size and number of continuation cards. Vectorizing certain operations in BANDIT, makes BANDIT run twice as fast in some large problems using structural elements with many node points. BANDIT is a built-in NASTRAN processor that optimizes the structural matrix bandwidth. The VAX matrix packing routine BLDPK was modified so that it is now packing a column of a matrix 3 to 9 times faster. The denser and bigger the matrix, the greater is the speed improvement. This improvement makes a host of routines and modules that involve matrix operation run significantly faster, and saves disc space for dense matrices. A UNIX version, converted from 1988 COSMIC/NASTRAN, was tested successfully on a Silicon Graphics computer using the UNIX V Operating System, with Berkeley 4.3 Extensions. The Utility Modules INPUTT5 and OUTPUT5 were expanded to handle table data, as well as matrices. Both INPUTT5 and OUTPUT5 are general input/output modules that read and write FORTRAN files with or without format. More user informative messages are echoed from PARAMR, PARAMD, and SCALAR modules to ensure proper data values and data types being handled. Two new Utility Modules, GINOFILE and DATABASE, were written for the 1989 release. Seven rigid elements are added to COSMIC/NASTRAN. They are: CRROD, CRBAR, CRTRPLT, CRBE1, CRBE2, CRBE3, and CRSPLINE.

Chan, Gordon C.↗