Global Arrays <description><url>http://www.emsl.pnl.gov:2080/docs/global/ga.html</url> The Global Array (GA) toolkit provides an efficient and portable "shared-memory" programming interface for distributed-memory computers. Each process in a MIMD parallel program can asynchronously access logical blocks of physically distributed matrices, without need for explicit cooperation by other processes. Unlike other shared-memory environments, the GA model exposes to the programmer the Non-Uniform Memory Access (NUMA) characteristics of the High Performance Computers and acknowledges that access to remote data is slower than to local data. Very efficient access to the local data is supported. The package is targeted to a class of applications in computational chemistry (specifically, computation of the electronic structure crystalline chemical systems). GA applications may be written in C or Fortran 77. The package includes a tool for trace-based animation and visualization of accesses to distributed arrays. <keywords>virtual shared memory; MIMD machine; nonuniform memory access; distributed array; execution trace visualization; parallel programming library <category>ppt-pplib <environment> PROGRAMMING INTERFACE: Fortran 77, C; only Fortran (1-based) array indexing is supported COMMUNICATION HARNESS: Interrupt-driven communication system on distributed memory message-passing machines TCGMSG (using a data-sever model) on networked workstations PLATFORMS SUPPORTED: Intel Gamma, Delta, Paragon; SP-1; KSR-1; SGI, SUN Workstation clusters <application> Computational chemistry - electronic structure computation of small or crystalline structures </urc>