BRIAN%UOFT02.BITNET@wiscvm.wisc.edu (03/28/87)
I'm sure this will come as no surprise to VAX C users, but I have realized substantial savings in execution time by replacing pattern matching and string copying routines with Macro-32 routines that take advantage of the Vaxen's character instructions. In the global sense, the speed improvement is minimal, however, the improvements realized in the specific case of pattern matching appears to the user to make a search pattern execute in a fraction of the time that a vanilla C coding would use. This approach is also used in DEC's TPU, which uses inline Macro-32 escapes from the Bliss code. When one really gets down to it, the next level of improvement would come from replacing the CALLS overhead with the much faster JSB, which is not possible in VAX C. The overhead from CALLS is substantial. Note that in the case of the VAX, the low end processors may not realize this since those machines tend to emulate some of the string op codes. Brian Nelson
meissner@dg_rtp.UUCP (03/31/87)
In article <6156@brl-adm.ARPA> BRIAN%UOFT02.BITNET@wiscvm.wisc.edu writes: > > I'm sure this will come as no surprise to VAX C users, but I have > realized substantial savings in execution time by replacing pattern > matching and string copying routines with Macro-32 routines that take > advantage of the Vaxen's character instructions. In the global sense, > the speed improvement is minimal, however, the improvements realized in > the specific case of pattern matching appears to the user to make a > search pattern execute in a fraction of the time that a vanilla C coding > would use. I don't doubt that you got a speed up, but check out the James Woods version of egrep (volume 4 in mod.sources, and a newer faster version promised real soon). His version (in C, no asm) manages to beat versions that use the VAX instructions in the general case. The new version is supposed to beat the assembly versions in all cases I think. It runs ten times faster than the standard System V egrep on my machine (no that is not a typo!). -- Michael Meissner, Data General Uucp: ...mcnc!rti-sel!dg_rtp!meissner It is 11pm, do you know what your sendmail and uucico are doing?