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Forum Index : Microcontroller and PC projects : Limits of variable names
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| karjo238 Regular Member  Joined: 12/10/2018 Location: New ZealandPosts: 54 |
Just a quick update to my story. I pressed on and managed to get the code running in MMBasic 5. I now just have to think in the new paradigm of coding that it brings along  Many thanks for everybodys help. Joseph. |
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Turbo46 Guru  Joined: 24/12/2017 Location: AustraliaPosts: 1636 |
That's good. Sorry about the sidetrack I caused with the integer thing but I learnt something from it anyway. Don't suppose you'd like to share it? Bill Keep safe. Live long and prosper. |
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thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4245 |
I might be wrong to resurrect this thread and I hate to second guess other programmers, but is there a good reason for this, seems like there are more efficient schemes. e.g. 1. Separate lists for variables beginning A, B, C, ... 2. Having the single character variables stored separately and in fixed locations so they can be looked up with a single indirection. 3. Combine 1 & 2 by having separate lists per leading character sorted alphabetically ... that way a single character variable can be looked up with one indirection and the longer names can be looked up with a binary chop. 4. Hash maps and other more complex data structures. 1 & 2 are what made BBC BASIC so fast compared to its peers. Regards, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3267 |
Some time ago I did a lot of benchmarking of MMBasic to discover where it spent most of its time and then I optimised the parts which wasted most of the time. This provided a useful performance boost. I cannot remember where variable lookup sat in the list but it was not very high. This is because typically most programs don't have that many variables and a linear search does a reasonably good job without the overhead and wasted flash space used by more complicated schemes. Recently Peter Mather discovered a small tweak for the search algorithm which does speed it up somewhat and I will include it in the next release. But for a typical program the overall improvement will be small. Geoff Geoff Graham - http://geoffg.net |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4245 |
Thanks for taking the time to answer Geoff, I guess this has been asked before. I asked because I've just found that the most effective optimisations I can make to my MMBasic (4.5) code are those that reduce variable lookups, of course they also reduce the amount of parsing, so it's not a simple equation. Maybe one of these days the kids will give me time to poke at the C myself so I can satisfy my curiosity Are the optimisations you talk about in MMBasic 4.5 as on the Colour Maximite, or only in MMBasic 5.x on the Micromites? Best wishes, Tom Edited 2020-04-29 20:22 by thwill MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3267 |
Yes, most of the optimisations were made back in V4.5 so they apply to the Maximite family. A couple more have been made since then but they do not make a great difference. My view has always been that interpreted BASIC has an inherent issue with speed and while you can tweak it you will never make it really fast. If fast is what you need then writing in C or assembler is the only real answer. Geoff Geoff Graham - http://geoffg.net |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4245 |
OK, thanks. In my professional capacity I agree with you, but with my hobbyist hat on I think on a modern processor / micro-controller an interpreted language can be fast enough for most purposes (see all the usage of Python, admittedly semi-compiled). Especially if you can fallback to native code for critical routines ... alas not possible on the Maximite Thanks again, Tom MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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