Add scratchpad
This commit is contained in:
Abdelrahman Said
@@ -0,0 +1,327 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#include "../src/wapp/wapp.h"
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/* ---------------------------------------------------------------------------
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* Pool allocator (arena-backed, intrusive free list)
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* -------------------------------------------------------------------------*/
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typedef struct PrPoolFreeNode PrPoolFreeNode;
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struct PrPoolFreeNode {
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PrPoolFreeNode *next;
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};
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typedef struct {
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WpAllocator *allocator;
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PrPoolFreeNode *free_head;
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u64 slot_size;
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} PrPool;
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static void prPoolInit(PrPool *pool, WpAllocator *arena, u64 slot_size) {
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pool->allocator = arena;
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pool->free_head = NULL;
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pool->slot_size = slot_size;
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}
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static void *prPoolAlloc(PrPool *pool) {
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if (pool->free_head) {
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PrPoolFreeNode *node = pool->free_head;
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pool->free_head = node->next;
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return node;
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}
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return wpMemAllocatorAlloc(pool->allocator, pool->slot_size);
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}
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static void prPoolFree(PrPool *pool, void *slot) {
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if (!slot) { return; }
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PrPoolFreeNode *node = (PrPoolFreeNode *)slot;
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node->next = pool->free_head;
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pool->free_head = node;
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}
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/* ---------------------------------------------------------------------------
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* Graph — unified nodes with values + forward/backward adjacency
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*
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* - Nodes live in a flat array; free slots are linked via next_free.
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* - Each node has a generation counter bumped on free; handles are
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* { index, generation } so stale references are detectable.
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* - Edges are pool-allocated PrEdgeNode structs with both forward
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* and backward linkage so deletion traces both directions.
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* -------------------------------------------------------------------------*/
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#define PR_INVALID_INDEX ((u64)-1)
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typedef struct PrEdgeNode PrEdgeNode;
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struct PrEdgeNode {
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PrEdgeNode *pool_next; /* used by pool free list when freed */
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PrEdgeNode *next_forward; /* chain in source's forward list */
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PrEdgeNode *next_backward; /* chain in target's backward list */
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u64 source_idx;
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u64 target_idx;
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};
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typedef struct {
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u64 index;
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u64 generation;
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} PrHandle;
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typedef struct {
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int value;
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u64 generation; /* bumped on every free */
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u64 next_free; /* free-list index (PR_INVALID_INDEX = active) */
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PrEdgeNode *forward_head; /* outgoing edges */
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PrEdgeNode *backward_head; /* incoming edges */
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} PrGraphNode;
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typedef struct {
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PrGraphNode *nodes; /* WpArray of PrGraphNode */
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u64 max_nodes;
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u64 max_ever; /* highest index ever allocated */
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u64 free_head; /* PR_INVALID_INDEX = empty */
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u64 count; /* active node count */
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PrPool edge_pool;
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} PrGraph;
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/* --- initialisation ---------------------------------------------------- */
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static void prGraphInit(PrGraph *g, WpAllocator *arena, u64 max_nodes) {
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g->nodes = wpArrayAllocCapacity(PrGraphNode, arena, max_nodes, WP_ARRAY_INIT_FILLED);
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g->max_nodes = max_nodes;
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g->max_ever = 0;
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g->free_head = PR_INVALID_INDEX;
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g->count = 0;
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prPoolInit(&g->edge_pool, arena, sizeof(PrEdgeNode));
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/* Build the free list — last slot's next_free stays PR_INVALID_INDEX */
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for (u64 i = 0; i < max_nodes; i++) {
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g->nodes[i].next_free = (i < max_nodes - 1) ? i + 1 : PR_INVALID_INDEX;
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}
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g->free_head = 0;
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}
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/* --- handle validation ------------------------------------------------ */
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static b8 prHandleValid(PrGraph *g, PrHandle h) {
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if (h.index >= g->max_nodes) { return false; }
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PrGraphNode *node = &g->nodes[h.index];
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return node->generation == h.generation && node->next_free == PR_INVALID_INDEX;
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}
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/* --- node management -------------------------------------------------- */
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static PrHandle prNodeAdd(PrGraph *g, int value) {
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if (g->free_head == PR_INVALID_INDEX) {
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return (PrHandle){ PR_INVALID_INDEX, 0 };
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}
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u64 idx = g->free_head;
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PrGraphNode *n = &g->nodes[idx];
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g->free_head = n->next_free;
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n->value = value;
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n->next_free = PR_INVALID_INDEX;
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n->forward_head = NULL;
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n->backward_head = NULL;
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g->count++;
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if (idx >= g->max_ever) { g->max_ever = idx + 1; }
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return (PrHandle){ idx, n->generation };
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}
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static int *prNodeGetValue(PrGraph *g, PrHandle h) {
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if (!prHandleValid(g, h)) { return NULL; }
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return &g->nodes[h.index].value;
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}
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/* --- internal: unlink edge helpers ------------------------------------ */
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static PrEdgeNode *_unlinkForward(PrGraph *g, u64 from_idx, u64 target_idx) {
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PrGraphNode *src = &g->nodes[from_idx];
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PrEdgeNode *prev = NULL;
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PrEdgeNode *curr = src->forward_head;
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while (curr) {
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if (curr->target_idx == target_idx) {
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if (prev) { prev->next_forward = curr->next_forward; }
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else { src->forward_head = curr->next_forward; }
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return curr;
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}
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prev = curr;
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curr = curr->next_forward;
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}
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return NULL;
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}
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static void _unlinkBackward(PrGraph *g, u64 to_idx, u64 source_idx) {
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PrGraphNode *dst = &g->nodes[to_idx];
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PrEdgeNode *prev = NULL;
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PrEdgeNode *curr = dst->backward_head;
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// This is intended to handle cases where the target node might not be the one
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// immediately feeding the node represented by to_idx
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while (curr) {
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if (curr->source_idx == source_idx) {
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if (prev) { prev->next_backward = curr->next_backward; }
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else { dst->backward_head = curr->next_backward; }
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return;
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}
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prev = curr;
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curr = curr->next_backward;
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}
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}
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/* --- edge management -------------------------------------------------- */
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static b8 prEdgeAdd(PrGraph *g, PrHandle from, PrHandle to) {
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if (!prHandleValid(g, from) || !prHandleValid(g, to)) { return false; }
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PrEdgeNode *edge = (PrEdgeNode *)prPoolAlloc(&g->edge_pool);
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if (!edge) { return false; }
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edge->source_idx = from.index;
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edge->target_idx = to.index;
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PrGraphNode *src = &g->nodes[from.index];
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edge->next_forward = src->forward_head;
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src->forward_head = edge;
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PrGraphNode *dst = &g->nodes[to.index];
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edge->next_backward = dst->backward_head;
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dst->backward_head = edge;
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return true;
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}
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/* --- node removal (tears down incident edges) ------------------------- */
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static void prNodeRemove(PrGraph *g, PrHandle h) {
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if (!prHandleValid(g, h)) { return; }
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u64 idx = h.index;
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PrGraphNode *n = &g->nodes[idx];
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/* Free outgoing edges: unlink from each target's backward list */
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PrEdgeNode *edge = n->forward_head;
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while (edge) {
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PrEdgeNode *next = edge->next_forward;
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_unlinkBackward(g, edge->target_idx, idx);
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prPoolFree(&g->edge_pool, edge);
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edge = next;
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}
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/* Free incoming edges: unlink from each source's forward list */
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edge = n->backward_head;
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while (edge) {
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PrEdgeNode *next = edge->next_backward;
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/* edge is also in the source's forward list — unlink by target_idx */
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_unlinkForward(g, edge->source_idx, idx);
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prPoolFree(&g->edge_pool, edge);
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edge = next;
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}
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/* Return node slot to free list with bumped generation */
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n->generation++;
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n->next_free = g->free_head;
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g->free_head = idx;
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g->count--;
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}
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/* --- traversal helpers ------------------------------------------------ */
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static void prDump(PrGraph *g) {
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printf("Active nodes: %llu\n\n", (unsigned long long)g->count);
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for (u64 i = 0; i < g->max_ever; i++) {
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PrGraphNode *n = &g->nodes[i];
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if (n->next_free != PR_INVALID_INDEX) { continue; }
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printf(" [%llu] g=%llu value=%d\n",
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(unsigned long long)i,
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(unsigned long long)n->generation,
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n->value);
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printf(" forward ──▶");
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PrEdgeNode *e = n->forward_head;
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if (!e) { printf(" (none)"); }
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while (e) {
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PrGraphNode *tv = &g->nodes[e->target_idx];
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printf(" %llu[%d]", (unsigned long long)e->target_idx, tv->value);
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e = e->next_forward;
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if (e) { printf(","); }
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}
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printf("\n");
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printf(" backward ◀──");
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e = n->backward_head;
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if (!e) { printf(" (none)"); }
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while (e) {
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PrGraphNode *sv = &g->nodes[e->source_idx];
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printf(" %llu[%d]", (unsigned long long)e->source_idx, sv->value);
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e = e->next_backward;
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if (e) { printf(","); }
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}
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printf("\n");
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}
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}
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/* ---------------------------------------------------------------------------
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* Demo
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* -------------------------------------------------------------------------*/
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int main(void) {
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srand((unsigned)time(NULL));
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WpAllocator arena = wpMemArenaAllocatorInitZero(KiB(64));
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if (wpMemAllocatorInvalid(&arena)) {
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fprintf(stderr, "arena init failed\n");
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return 1;
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}
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PrGraph g;
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prGraphInit(&g, &arena, 16);
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printf("=== Add 6 nodes ===\n");
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PrHandle nodes[10];
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for (u64 i = 0; i < 6; i++) {
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nodes[i] = prNodeAdd(&g, rand() % 100);
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printf(" node[%llu] = handle{%llu g%llu} val=%d\n",
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(unsigned long long)i,
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(unsigned long long)nodes[i].index,
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(unsigned long long)nodes[i].generation,
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*prNodeGetValue(&g, nodes[i]));
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}
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printf("\n=== Add edges: 0→1, 0→2, 1→3, 2→3, 3→4, 4→5 ===\n");
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u64 edge_list[][2] = { {0,1}, {0,2}, {1,3}, {2,3}, {3,4}, {4,5} };
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for (u64 i = 0; i < 6; i++) {
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u64 f = edge_list[i][0], t = edge_list[i][1];
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prEdgeAdd(&g, nodes[f], nodes[t]);
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}
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prDump(&g);
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printf("=== Remove node 2 (index %llu) ===\n",
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(unsigned long long)nodes[2].index);
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prNodeRemove(&g, nodes[2]);
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prDump(&g);
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printf("=== Stale check ===\n");
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printf(" nodes[2] handle{%llu g%llu} valid? %s\n",
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(unsigned long long)nodes[2].index,
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(unsigned long long)nodes[2].generation,
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prHandleValid(&g, nodes[2]) ? "YES" : "NO");
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printf("=== Add edge 5→0 (reuses freed edge slots) ===\n");
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prEdgeAdd(&g, nodes[5], nodes[0]);
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prDump(&g);
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printf("=== Add a new node (reuses freed node slot) ===\n");
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nodes[6] = prNodeAdd(&g, 42);
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printf(" new node = handle{%llu g%llu} val=%d\n",
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(unsigned long long)nodes[6].index,
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(unsigned long long)nodes[6].generation,
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*prNodeGetValue(&g, nodes[6]));
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prDump(&g);
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wpMemArenaAllocatorDestroy(&arena);
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return 0;
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}
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