[Microbit-Python] memory error

[David Whale]

I only had a 1K ZX81 and it forced me to learn machine code so I could make
everything fit :)

I'm *guessing* that MicroPython has a fixup table, so that the variable
names and function names are only stored in RAM once - i.e. each reference
to a function name or variable name in the bytecode is actually an index
into a string table with the actual name in it? Perhaps a one-way hash
could be used to turn any given name into a shorter hash that is actually
used for the lookup?

Cheers

D


___________________________________________________________
David Whale, B.Sc (Hons), MIET
*Software Engineer and IET Schools Liaison Officer, Essex*

email:  dwhale at theiet.org
twitter: @whaleygeek
blog:  blog.whaleygeek.co.uk

Co-author of the new book "Adventures in Minecraft" <http://amzn.to/ZGfxZG>
- lets get kids coding!


On 2 October 2015 at 18:06, Alan <alainjackson at hotmail.com> wrote:

> Hi,
>
> Am I right in thinking the size of variable names also makes a difference?
> It seemed to, although I didn't test that scientifically.
>
> 3KB is a bit small. I know, however big the memory we'd always want more.
> And I did grow up programming a ZX81, so this is 3 times as big! You'd
> think I'd be happy with that.
>
> Cheers,
>
> Alan
>
> > Date: Fri, 2 Oct 2015 16:07:02 +0100
>
> > From: damien.p.george at gmail.com
> > To: microbit at python.org
> > Subject: Re: [Microbit-Python] memory error
> >
> > Hi Alan,
> >
> > Yes, doc strings do take up memory, so in our case (when trying to
> > reduce memory usage) it's better to make them comments (which are just
> > skipped over by the tokeniser).
> >
> > The example you give with lots of prints does indeed take up all the
> > memory, so that's why it gives a MemoryError. It's not easy to fix
> > this, the microbit is just really low on RAM! We could compile the
> > python script to flash (instead of RAM) but that needs a bit of effort
> > to get working.
> >
> > Cheers,
> > Damien.
> >
> >
> > On Thu, Oct 1, 2015 at 2:52 AM, Alan <alainjackson at hotmail.com> wrote:
> > > Hi,
> > >
> > > Another little trick I've realised is that if I put a large,
> explanatory
> > > comment at the top of the file using """...""" it of course goes into a
> > > docstring... which takes up memory!
> > >
> > > If I use # style comments instead, it doesn't seem to take up memory.
> > >
> > > Cheers,
> > >
> > > Alan
> > >
> > > ________________________________
> > > From: alainjackson at hotmail.com
> > > To: microbit at python.org
> > > Date: Thu, 1 Oct 2015 00:32:14 +0000
> > >
> > > Subject: Re: [Microbit-Python] memory error
> > >
> > > Hi,
> > >
> > > I didn't save the version of my code that got the memory error.
> > >
> > > But I've just now created a small, pathological example.
> > >
> > > The code below, which is 3kB on the disk, will create the following
> error:
> > >
> > >>>> MemoryError:
> > > Micro Python v1.4.5-68-g3a2171e on 2015-09-04; micro:bit with nRF51822
> > > Type "help()" for more information.
> > >
> > > But if you delete the last line, it will run fine.
> > >
> > >
> > >
> > >
> > > """
> > > Testing how much memory for python code the microbit has.
> > > """
> > >
> > > from microbit import *
> > >
> > >
> > >
> > >
> > >
> display.print("123456789022345678903234567890423456789052345678906234567890723456789082345678909234567890")
> > >
> display.print("a12345678902234567890323456789042345678905234567890623456789072345678908234567890923456789")
> > >
> display.print("ba1234567890223456789032345678904234567890523456789062345678907234567890823456789092345678")
> > >
> display.print("cba123456789022345678903234567890423456789052345678906234567890723456789082345678909234567")
> > >
> display.print("dcba12345678902234567890323456789042345678905234567890623456789072345678908234567890923456")
> > >
> display.print("ecba12345678902234567890323456789042345678905234567890623456789072345678908234567890923456")
> > >
> display.print("fecba1234567890223456789032345678904234567890523456789062345678907234567890823456789092345")
> > >
> display.print("gfecba123456789022345678903234567890423456789052345678906234567890723456789082345678909234")
> > >
> display.print("hgfecba12345678902234567890323456789042345678905234567890623456789072345678908234567890923")
> > >
> display.print("ihgfecba1234567890223456789032345678904234567890523456789062345678907234567890823456789092")
> > >
> display.print("123456789022345678903234567890423456789052345678906234567890723456789082345678909234567890")
> > >
> display.print("a12345678902234567890323456789042345678905234567890623456789072345678908234567890923456789")
> > >
> display.print("ba1234567890223456789032345678904234567890523456789062345678907234567890823456789092345678")
> > >
> display.print("cba123456789022345678903234567890423456789052345678906234567890723456789082345678909234567")
> > >
> display.print("dcba12345678902234567890323456789042345678905234567890623456789072345678908234567890923456")
> > >
> display.print("ecba12345678902234567890323456789042345678905234567890623456789072345678908234567890923456")
> > >
> display.print("fecba1234567890223456789032345678904234567890523456789062345678907234567890823456789092345")
> > >
> display.print("gfecba123456789022345678903234567890423456789052345678906234567890723456789082345678909234")
> > >
> display.print("hgfecba12345678902234567890323456789042345678905234567890623456789072345678908234567890923")
> > >
> display.print("ihgfecba1234567890223456789032345678904234567890523456789062345678907234567890823456789092")
> > >
> display.print("123456789022345678903234567890423456789052345678906234567890723456789082345678909234567890")
> > >
> display.print("a12345678902234567890323456789042345678905234567890623456789072345678908234567890923456789")
> > >
> display.print("ba1234567890223456789032345678904234567890523456789062345678907234567890823456789092345678")
> > >
> display.print("cba123456789022345678903234567890423456789052345678906234567890723456789082345678909234567")
> > >
> display.print("dcba12345678902234567890323456789042345678905234567890623456789072345678908234567890923456")
> > >
> display.print("ecba12345678902234567890323456789042345678905234567890623456789072345678908234567890923456")
> > >
> display.print("fecba1234567890223456789032345678904234567890523456789062345678907234567890823456789092345")
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >> Date: Wed, 30 Sep 2015 12:01:57 +0100
> > >> From: damien.p.george at gmail.com
> > >> To: microbit at python.org
> > >> Subject: Re: [Microbit-Python] memory error
> > >>
> > >> Hi Alan,
> > >>
> > >> Can you post your code?
> > >>
> > >> On Wed, Sep 30, 2015 at 2:14 AM, Alan <alainjackson at hotmail.com>
> wrote:
> > >> > Hi,
> > >> >
> > >> > How much memory does the Microbit have for a python program?
> > >> >
> > >> > I've written a small program about 105 lines long. It's 3kB on my
> hard
> > >> > disk.
> > >> > It runs ok now but when it was 115 lines long and 3.2kB I kept
> getting
> > >> > memory allocation errors as soon as I pressed the reset button. If I
> > >> > commented about 10 lines out of my program it would run and it
> didn't
> > >> > seem
> > >> > to matter which 10 lines. So I assumed it was out of program memory?
> > >> >
> > >> > Cheers,
> > >> >
> > >> > Alan
> > >> >
> > >> > _______________________________________________
> > >> > Microbit mailing list
> > >> > Microbit at python.org
> > >> > https://mail.python.org/mailman/listinfo/microbit
> > >> >
> > >> _______________________________________________
> > >> Microbit mailing list
> > >> Microbit at python.org
> > >> https://mail.python.org/mailman/listinfo/microbit
> > >
> > > _______________________________________________ Microbit mailing list
> > > Microbit at python.org https://mail.python.org/mailman/listinfo/microbit
> > >
> > > _______________________________________________
> > > Microbit mailing list
> > > Microbit at python.org
> > > https://mail.python.org/mailman/listinfo/microbit
> > >
> > _______________________________________________
> > Microbit mailing list
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> > https://mail.python.org/mailman/listinfo/microbit
>
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