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⚡ Bolt: [td_to_vakt performans iyileştirmesi] #34

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⚡ Bolt: [td_to_vakt performans iyileştirmesi] #34

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15 changes: 6 additions & 9 deletions .jules/bolt.md
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Original file line number Diff line number Diff line change
@@ -1,10 +1,7 @@
## 2026-05-03 - [Optimize XML Parsing via Lazy Initialization]
**Learning:** In C++ codebases like Vasati that heavily rely on parsing large XML datasets (e.g., `Vakitler.xml` using `pugixml`), parsing the document repeatedly upon every instantiation of a core class (`zaman`) creates a massive performance bottleneck.
**Action:** Implemented lazy initialization (a `static bool is_loaded` flag along with making `pugi::xml_document` and `pugi::xml_node` static members) so that the XML document is loaded only once per program lifecycle. This simple change yields a roughly ~3x performance boost for object instantiation (from ~3.8s down to ~1.1s for 10000 object instantiations).
## 2026-05-08 - [XML Parsing Optimization]
**Learning:** Parsing the XML document in the constructor of `zaman` class without caching causes a significant performance bottleneck (around 40ms per 100 instantiations). Repeatedly loading the file creates high overhead.
**Action:** Used a C++11 method-local magic static and an immediately invoked lambda to cache the `cityinfo` XML node (`zaman::sehir`), reducing 100 instantiations from ~40ms to ~14ms.
## 2024-05-24 - `zaman::td_to_vakt` and String Allocation Optimization
**Learning:** In C++, frequently called formatting functions like `td_to_vakt` and `zaman::sat_turk_v_d` that use multiple `std::to_string` allocations and string concatenations (`+` or `.append()`) suffer from high memory allocation overhead, creating severe memory and CPU bottlenecks.
**Action:** Replace dynamic allocations inside highly-called utility functions with manual, fixed-size stack buffers (`char buf[]`) and direct ASCII arithmetic (`'0' + value`) to entirely bypass temporary string objects. This reduces execution time significantly in string formatting benchmarks.

## 2024-05-11 - [XML Lookup Optimization]
**Learning:** Repeatedly calling `pugi::xml_node::find_child_by_attribute` to look up prayer times by `dayofyear` is an O(N) linear search bottleneck that slows down `zaman` class instantiations.
**Action:** Replaced it with an O(1) array lookup. Since `dayofyear` acts as a sequential 0-based index (0-365), we can cache the `const char*` text of each `prayertimes` node into a static `cached_nodes[400]` array using a magic static block. This reduced instantiation time nearly by half.
## 2024-05-24 - `zaman::td_to_vakt` and String Allocation Optimization
**Learning:** In C++, frequently called formatting functions like `td_to_vakt` and `zaman::sat_turk_v_d` that use multiple `std::to_string` allocations and string concatenations (`+` or `.append()`) suffer from high memory allocation overhead, creating severe memory and CPU bottlenecks.
**Action:** Replace dynamic allocations inside highly-called utility functions with manual, fixed-size stack buffers (`char buf[]`) and direct ASCII arithmetic (`'0' + value`) to entirely bypass temporary string objects. This reduces execution time significantly in string formatting benchmarks.
44 changes: 26 additions & 18 deletions src/src-class/Zaman.cpp
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Expand Up @@ -70,7 +70,26 @@ unsigned int zaman::vakt_to_td(const std::string& vakt)

std::string zaman::td_to_vakt(unsigned int td)
{
return std::to_string(int(td / 60) % 12) + ":" + std::to_string(int(td % 60));
// ⚡ Bolt Optimizasyonu: std::to_string() yerine sabit boyutlu stack buffer kullanarak
// heap tahsisi ve string birleştirme masrafını (allocation overhead) ortadan kaldırdık.
char buf[6];
int h = int(td / 60) % 12;
int m = int(td % 60);
int pos = 0;
if (h >= 10) {
buf[pos++] = '0' + (h / 10);
buf[pos++] = '0' + (h % 10);
} else {
buf[pos++] = '0' + h;
}
buf[pos++] = ':';
if (m >= 10) {
buf[pos++] = '0' + (m / 10);
buf[pos++] = '0' + (m % 10);
} else {
buf[pos++] = '0' + m;
}
return std::string(buf, pos);
}

void zaman::vkt_h_v_d()
Expand All @@ -89,7 +108,7 @@ void zaman::vkt_h_v_d()

char buffer[5];

static const pugi::xml_node* cached_nodes = []() {
static const char** cached_nodes_text = []() {
static pugi::xml_document doc;
if (!doc.load_file("include/XML/Vakitler.xml") && !doc.load_file("vakitler.xml")) {
throw std::runtime_error("XML load failed");
Expand All @@ -99,28 +118,17 @@ void zaman::vkt_h_v_d()
throw std::runtime_error("Missing cityinfo node");
}

// ⚡ Bolt Optimizasyonu: XML düğümlerini 'dayofyear' özniteliğine göre önbelleğe alarak O(1) erişim sağla (O(N) doğrusal arama yerine)
// Her nesne örneği oluşturulduğunda O(N) doğrusal arama darboğazını ortadan kaldırır
static pugi::xml_node nodes[400];
static const char* texts[400] = {nullptr};
for (pugi::xml_node pt = node.child("prayertimes"); pt; pt = pt.next_sibling("prayertimes")) {
int day = pt.attribute("dayofyear").as_int(-1);
if (day >= 0 && day < 400) {
nodes[day] = pt;
texts[day] = pt.text().get();
}
}
return nodes;
}();

static const char* cached_nodes[400] = {nullptr};
static bool cached_nodes_init = []() {
for (pugi::xml_node pt = cached_sehir.child("prayertimes"); pt; pt = pt.next_sibling("prayertimes")) {
int day = std::atoi(pt.attribute("dayofyear").value());
if (day >= 0 && day < 400) cached_nodes[day] = pt.text().get();
}
return true;
return texts;
}();

zaman::xml_bu_gun = (zaman::h_rakam_gun_senenin >= 0 && zaman::h_rakam_gun_senenin < 400 && cached_nodes[zaman::h_rakam_gun_senenin]) ? cached_nodes[zaman::h_rakam_gun_senenin] : "";
zaman::xml_bu_gun = (zaman::h_rakam_gun_senenin >= 0 && zaman::h_rakam_gun_senenin < 400 && cached_nodes_text[zaman::h_rakam_gun_senenin]) ? cached_nodes_text[zaman::h_rakam_gun_senenin] : "";

zaman::h_aksam = zaman::xml_bu_gun.substr(50, 6);
zaman::h_istibak_nucum = zaman::xml_bu_gun.substr(56, 6);
Expand All @@ -130,7 +138,7 @@ void zaman::vkt_h_v_d()
//buradaka kodları yeniliyoruz çünkü bir sonraki gün kılacağız verileri:

int next_day = zaman::h_rakam_gun_senenin + 1;
zaman::xml_bu_gun = (next_day >= 0 && next_day < 400 && cached_nodes[next_day]) ? cached_nodes[next_day] : "";
zaman::xml_bu_gun = (next_day >= 0 && next_day < 400 && cached_nodes_text[next_day]) ? cached_nodes_text[next_day] : "";

zaman::h_imsak = zaman::xml_bu_gun.substr(0, 4) ;
zaman::h_sabah = zaman::xml_bu_gun.substr(5, 5) ;
Expand Down