Yes, Raul. It was a stupid J expression. Wasn't thinking about what I wrote, but I was thinking about what I was told when I first learned APL, "Often it is better to go ahead and calculate a result, then throw it away, than try to figure out if you really need the calculation".
I brought up AVX because it makes that observation even more true. Working with the IBM 370 vector unit many years ago, it could process arrays at what was an unbelievable speed at that time. Of course, not any more. But it was extremely important to "not interrupt the pipeline". Setting up a vector unit operation was expensive but once going it flew. It presented a dilemma because the setting up an instruction was expensive and it didn't work well for short vectors. But it was implemented into APL2. It worked well, but made even more true what I first learned in APL for the 1130, where (I think) the game of APL one-liners began. Hopefully, the instruction setup for AVX is easier and more efficient than the 370 vector unit, but even so, it is probably very important to not interrupt the instruction and let it run on as long of vectors as it can. So, I was trying to illustrate the effort to remove numbers from the vector that wouldn't be used in the final result. It would be so much trouble and require so much compressing and expanding that it would be better to "just calculate the result and throw it away later". The idea of skipping calculation that will never be used is useful in some cases, but can easily spend more time determining whether to skip than going ahead with the calculation. This is particularly true in the world of arrays. Making it an important requirement only works in a scalar world, and is questionable even then and easily made incorrect as hardware is enhanced. On Wed, Nov 8, 2017 at 2:15 AM, Erling Hellenäs <[email protected]> wrote: > I don't need anything. The discussion was not about any question of mine. > The discussion ended, so I guess the people having questions got their > answers. /Erling > > > Den 2017-11-08 kl. 10:02, skrev Raul Miller: > >> Please let me know what you need beyond the information I laid out in >> http://jsoftware.com/pipermail/programming/2017-November/049599.html >> >> Thanks, >> >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
