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Turns out that passing dom::element by reference can be a performance killer. (#1086)

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* Turns out that passing dom::element by reference can be a performance killer.

* Tweaking.
This commit is contained in:
Daniel Lemire
2020-08-01 10:31:47 -04:00
committed by GitHub
parent 54ed24f481
commit 2f92a34bb7
2 changed files with 10 additions and 3 deletions
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benchmark/parseandstatcompetition.cpp
+3 -2
View File
@@ -131,7 +131,7 @@ struct Stat {
size_t stringLength; // Number of code units in all strings
};
static void GenStatPlus(Stat &stat, const dom::element &v) {
static void GenStatPlus(Stat &stat, const dom::element v) {
switch (v.type()) {
case dom::element_type::ARRAY:
for (dom::element child : dom::array(v)) {
@@ -142,7 +142,8 @@ static void GenStatPlus(Stat &stat, const dom::element &v) {
break;
case dom::element_type::OBJECT:
for (dom::key_value_pair kv : dom::object(v)) {
GenStatPlus(stat, dom::element(kv.value));
GenStatPlus(stat, kv.value);
stat.stringLength += kv.key.size();
stat.memberCount++;
stat.stringCount++;
}
doc/performance.md
+7 -1
View File
@@ -12,7 +12,7 @@ are still some scenarios where tuning can enhance performance.
* [Number parsing](#number-parsing)
* [Visual Studio](#visual-studio)
* [Downclocking](#downclocking)
* [Best Use of the DOM API](#best-use-of-the-dom-api)
Reusing the parser for maximum efficiency
-----------------------------------------
@@ -181,3 +181,9 @@ On some Intel processors, using SIMD instructions in a sustained manner on the s
The simdjson library does not currently support AVX-512 instructions and it does not make use of heavy 256-bit instructions. We do use vectorized multiplications, but only using 128-bit registers. Thus there should be no downclocking due to simdjson on recent processors.
You may still be worried about which SIMD instruction set is used by simdjson. Thankfully, [you can always determine and change which architecture-specific implementation is used](implementation-selection.md) by simdjson. Thus even if your CPU supports AVX2, you do not need to use AVX2. You are in control.
Best Use of the DOM API
-------------------------
The simdjson API provides access to the JSON DOM (document-object-model) content as a tree of `dom::element` instances, each representing an object, an array or an atomic type (null, true, false, number). These `dom::element` instances are lightweight objects (e.g., spanning 16 bytes) and it might be advantageous to pass them by value, as opposed to passing them by reference or by pointer.