Path: utzoo!utgpu!water!watmath!clyde!ima!necntc!ames!lamaster From: lamaster@ames.arc.nasa.gov (Hugh LaMaster) Newsgroups: comp.arch Subject: Re: Dhrystone 2.1 discounts segment thrashing Keywords: integer benchmark Message-ID: <11722@ames.arc.nasa.gov> Date: 13 Jul 88 17:57:58 GMT References: <517@pcrat.UUCP> <2294@sugar.UUCP> Reply-To: lamaster@ames.arc.nasa.gov.UUCP (Hugh LaMaster) Organization: NASA Ames Research Center, Moffett Field, Calif. Lines: 33 In article <2294@sugar.UUCP> karl@sugar.UUCP (Karl Lehenbauer) writes: >computers in comp.arch may notice that many machines based on the Intel >80286 performed extraordinarily well in the tests, exceeding the performance >of low-end Vaxes, 68000s, etc, and approaching the peformance of 386 machines. >This runs strongly counter to my personal experience with these machines. > VAX-11/750 6.11 13.13 > IBM PC AT 8.13 99.71 >I'd like to see a future version of Dhrystone include a something like this, >whereby a certain amount of processing of an array is performed for different >array sizes, so that the thrashing nature small segmented architectures Rather than try to make Dhrystone the all inclusive benchmark, why not simply treat it for what it is: a simple test of CPU (as opposed to system) speed on simple branch, procedure call, and character intensive code. A much more serious criticism of Dhrystone, and many old and/or simple benchmarks, is that because there is no appearance to a smart compiler of output which depends on execution time calcutions, many smart optimizing compilers may start optimizing all the work away. This used to be a problem even on earlier compilers, such as the FTN compiler on the CDC 7600, in basic blocks inside loops. Globally optimizing compilers make the problem worse. You really need to compute something to print out which depends on all previous calculations in order to solve the problem completely. -- Hugh LaMaster, m/s 233-9, UUCP ames!lamaster NASA Ames Research Center ARPA lamaster@ames.arc.nasa.gov Moffett Field, CA 94035 Phone: (415)694-6117