b9b8cecbfc
The folded name logic (despite all attempts to optimize it) was fundamentally an O(n) operation where every field in a struct needed to be linearly scanned in order to find a match. This made unmashaling of unknown fields always O(n). Instead of optimizing the comparison for each field, make it such that we can look up a name in O(1). We accomplish this by maintaining a map keyed by pre-folded names, which we can pre-calculate when processing the struct type. Using a stack-allocated buffer, we can fold the input name and look up its presence in the map. Also, instead of mapping from names to indexes, map directly to a pointer to the field information. The memory cost of this is the same and avoids an extra slice index. The new logic is both simpler and faster. Performance: name old time/op new time/op delta CodeDecoder 2.47ms ± 4% 2.42ms ± 2% -1.83% (p=0.022 n=10+9) UnicodeDecoder 259ns ± 2% 248ns ± 1% -4.32% (p=0.000 n=10+10) DecoderStream 150ns ± 1% 149ns ± 1% ~ (p=0.516 n=10+10) CodeUnmarshal 3.13ms ± 2% 3.09ms ± 2% -1.37% (p=0.022 n=10+9) CodeUnmarshalReuse 2.50ms ± 1% 2.45ms ± 1% -1.96% (p=0.001 n=8+9) UnmarshalString 67.1ns ± 5% 64.5ns ± 5% -3.90% (p=0.005 n=10+10) UnmarshalFloat64 60.1ns ± 4% 58.4ns ± 2% -2.89% (p=0.002 n=10+8) UnmarshalInt64 51.0ns ± 4% 49.2ns ± 1% -3.53% (p=0.001 n=10+8) Issue10335 80.7ns ± 2% 79.2ns ± 1% -1.82% (p=0.016 n=10+8) Issue34127 28.6ns ± 3% 28.8ns ± 3% ~ (p=0.388 n=9+10) Unmapped 177ns ± 2% 177ns ± 2% ~ (p=0.956 n=10+10) Change-Id: I478b2b958f5a63a69c9a991a39cd5ffb43244a2a Reviewed-on: https://go-review.googlesource.com/c/go/+/471196 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Run-TryBot: Joseph Tsai <joetsai@digital-static.net> Auto-Submit: Joseph Tsai <joetsai@digital-static.net> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com> Reviewed-by: Than McIntosh <thanm@google.com> Reviewed-by: Daniel Martí <mvdan@mvdan.cc> |
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README.md
The Go Programming Language
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