Franz mentions Wirth's metric for compiler quality: Speed of self compilation. I first heard this idea, in a slightly different form, from Vickie Markstein (pa

Franz mentions Wirth's metric for compiler quality: Speed of self compilation. I first heard this idea, in a slightly different form, from Vickie Markstein (part of IBM's 801 team) in early '88. She suggested using this idea as an acid test for optimizations. For example, if the compiler with value numbering compiled itself faster than the compiler without value numbering, then she'd say value numbering was worthwhile. Given the organization of the 801 team, it's possible the idea was due to John Cocke or one of the other members. Doesn't matter much, I think. I've never had the opportunity to test optimizations using this approach, but I think it would be a fun way to approach the question of adding optimizations to something fast & simple like the Oberon compiler, the Plan 9 compiler, or the Go compiler. Indeed, for a _system_, like Oberon or Plan 9, where everything is compiled with the same compiler, we could go a step further and try adding the optimization, rebuilding everything, then timing the new compiler. That way any benefits the optimization brought to handling I/O and such would be properly credited and we'd (hopefully) see a steady improvement in the programmer's experience. Preston