[NTG-context] supp-ran.lua makes code unable to work in ConTeXt

[Hans Hagen]

On 5/1/2020 6:12 AM, Jairo A. del Rio wrote:
> I've adapted the following code to make mazes in LuaLaTeX and ConTeXt: 
> https://www.rosettacode.org/wiki/Maze_generation#Lua
> 
> I defined a modified version to make content visible to TeX and I saved 
> in a file named maze.lua:
> 
> function make_maze_tex(w, h, m)
>    w = w or 16
>    h = h or 8
> 
>    local map = initialize_grid(w*2+1, h*2+1)
> 
>    function walk(x, y)
>      map[y][x] = false
> 
>      local d = { 1, 2, 3, 4 }
>      shuffle(d)
>      for i, dirnum in ipairs(d) do
>        local xx = x + dirs[dirnum].x
>        local yy = y + dirs[dirnum].y
>        if map[yy] and map[yy][xx] then
>          map[avg(y, yy)][avg(x, xx)] = false
>          walk(xx, yy)
>        end
>      end
>    end
> 
>    walk(math.random(1, w)*2, math.random(1, h)*2)
> 
>   tex.print([[\bgroup]])
>   tex.print([[\baselineskip ]]..m)
>    local s = {}
>    for i = 1, h*2+1 do
>      --table.insert(s, [[\hbox{]])
>      tex.print([[\hbox{]])
>      for j = 1, w*2+1 do
>       -- table.insert(s, [[\hbox{]])
>        if (j == 1 and i == 2) or (j == 2*w + 1 and i == 2*h) then
>          tex.print([[\hskip ]]..m)
>        elseif map[i][j] then
>          --table.insert(s, [[\vrule width ]]..m..[[ height ]]..m)
>          tex.print([[\vrule width ]]..m..[[ height ]]..m)
>        else
>          --table.insert(s, [[\hskip ]]..m)
>          tex.print([[\hskip ]]..m)
>        end
>      --  table.insert(s, [[}]].."\n")
>      end
>      --table.insert(s, [[}]])
>    tex.print([[}]])
>    end
>   --tex.print(table.concat(s))
>   tex.print([[\egroup]])
> end
> 
> And I executed the folowing in LuaLaTeX and ConTeXt:
> 
> %\documentclass{article}
> %\usepackage{luacode}
> %\begin{document}
> \starttext
> %\begin{luacode*}
> \startluacode
> mz = dofile("maze.lua")
> local count = 0
> for i=10,109 do
> count = count + 1
> tex.print([[\subject{Laberinto ]]..count..[[}]])
> mz.make_maze_tex(i, i, [[\dimexpr\textwidth/]]..(2*i+1)..[[\relax]])
> tex.print([[\pagebreak]])
> end
> %\end{luacode*}
> \stopluacode
> %\end{document}
> \stoptext
> 
> Whereas it works very fast in LuaLaTeX it crashes on ConTeXt and outputs 
> the following:

btw, fast is relative ... no problem making the code twice as fast

it is actually a nice example for the cld manual ... attached some 
output from a first 'improvement' (that version runs some 50-60% faster 
so you have a challenge ... actually, it could be a nice challenge for 
others on this list: how to make this one contextish and so, maybe we 
should have a challenge every few weeks)

> token call, execute: 
> ...ext/tex/texmf-context/tex/context/base/mkiv/supp-ran.lua:30: C stack 
> overflow 
> 
> Why does it happen? I guess it has something to do with math.randomseed, 
> but I don't know how to avoid this error message.
no, it's just lua running out of stack space so it depends on the binary 
(and als the initial random value)

luatex 1.13 uses lua 5.3 which has a large stack but depending on the 
compiler/linker settings and platform (it's 1000000 but depending on the 
situatation you get a message or crash when that doesn't work out)

luajittex has a limited stack of 8000 so it will also crash

luametatex uses lua 5.4 which uses a bit different stack model and can't 
go that high (it has a default of 2000 but i will bnump that to 6000 
which still seems to work ok, that way i get upto a 120 maze)

(new lmtx upload later this weekend)

Hans

-----------------------------------------------------------------
                                           Hans Hagen | PRAGMA ADE
               Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
        tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
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