Optimise Recfile output generation
John Smith commited on 2022-214 13:37:56
Showing 1 changed files, with 12 additions and 6 deletions.
The Recfile-save function was painfully slow, perhaps accidentally quadratic, due to inefficiencies in string concatenation. Replacing a loop with a binary-tree recursion speeds it up greatly -- on my deck, the Recfile generation step now runs >18x faster.
- recrw.lua cd4c51a..b4e74ff
| ... | ... |
@@ -83,18 +83,24 @@ end |
| 83 | 83 |
returns (on success) a string |
| 84 | 84 |
returns (on failure) nil |
| 85 | 85 |
]] |
| 86 |
-local function recs2text(recs) |
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+local function recs2text(recs, si, ei) |
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| 87 | 87 |
local ret = "" |
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- -- go through records |
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- for i, rec in ipairs(recs) do |
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- for label, vl in pairs(rec) do |
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+ si = si or 1 |
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+ ei = ei or #recs |
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+ --[[ |
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+ use recursive (binary-splitting) string building |
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+ this makes stuff way more efficient |
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+ ]] |
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+ if si == ei then |
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+ for label, vl in pairs(recs[si]) do |
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| 91 | 96 |
for j, value in ipairs(vl) do |
| 92 | 97 |
ret = ret .. string.format("\n%s: %s", label, tostring(value):gsub("\n", "\n+ "))
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| 93 | 98 |
end |
| 94 | 99 |
end |
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- ret = ret .. "\n" |
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+ return ret .. "\n" |
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+ else |
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+ return recs2text(recs, si, (si + ei) // 2) .. recs2text(recs, (si + ei) // 2 + 1, ei) |
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| 96 | 103 |
end |
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- return ret |
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| 98 | 104 |
end |
| 99 | 105 |
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| 100 | 106 |
return { read = text2recs, write = recs2text }
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| 101 | 107 |