1. Elephant, Meet Penguin Stephen J. Gowdy Lawrence Berkeley National Lab For the BaBar Computing Group Bringing up Linux on BaBar

2. Linux - A BaBar Platform Commodity Computing Cheap? Many stages to process System issues (SoftRelTools, etc.) Porting Code base (2+ MLOC) Validation (ongoing) Outline Our reference Linux System Problems C++ Issues Fortran

3. Status Now a supported BaBar platform Adhoc validation done Production starting full validation Goal was to have support by 1st January 2000

4. The BaBar Reference Linux Based on RedHat 6.0 egcs 1.1.2 + patch Patch due to operator new in template class Lesstif 0.88.1 (version not critical) SLAC modification number of symlinks to follow max number of processes

5. Actual Machines Six Dell machines deployed at SLAC Dual Pentium III 550 MHz 1GB memory Two run build queues Mirror of Sun setup Three for interactive use One reserved for production building No batch machines as yet Price per machine similar to Sun for SLAC

6. System Troubles Operating system Missing system functions clock_gettime regcmp regex Missing defines SIGEMT & SIGSYS Online use only (which is only Sun) Build system SoftRelTools allowed easy extension Builds being done for 6 months

7. C++ Issues Extra temporaries Especially while constructing objects in method invocation Templates egcs requires inlined template definitions Some code did not follow guidelines Using operator T* must go via this-> No sync points in iostreams output cout << aMatrix << aMatrix.invert() << endl; egcs bugs Non-public destructors pow function with \O2 iostreams can't read 0x in hex numbers

8. FORTRAN No STRUCTUREs in FORTRAN77 Initially use Portland Compiler for 62 files Now these have been removed Many routines don't use SAVE Possible to overcome globally (compiler switch) Decided to fix these Symbols have different size -no_global to workaround these Performance penalty Cannot concatenating variable length strings Create temporaries

9. Conclusion Linux now deployed as a BaBar platform Complete validation ongoing Users feedback important Collaboration has significant CPU on Linux Not yet used by BaBar Remaining worries Objectivity builds not available for glibc 2.1 Large file support Not critical for our current operation procedures Rules out Linux servers for Objectivity at SLAC