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[muh] tuning_radix_sort: 148→211行, 基于 CCCL 2381 行源码完整重建 10-子策略架构

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从 CCCL tuning_radix_sort.cuh 读入完整 policy_selector::operator():
  SM100/SM90: make_onesweep_small_key_policy (benchmark-tuned entries)
  SM80: onesweep (key≥4B) + multi_pass (key<4B)
  SM70: onesweep (key≥4B) + multi_pass (key<4B) ← BI-V100 基线
  SM60: similar to SM70 with different params
  SM50: multi_pass only

BI-V100 选择 SM70 策略而非 SM100 的原因:
  1. HBM2 vs HBM3 — 内存子系统接近 V100
  2. onesweep 的 rank_private_partitions=4 (SM70) vs 1 (SM80+)
     SM80+ 有 hardware atomic 改进使 partition=1 可行
     BI-V100 atomic 性能未知, 保守用 SM70 的 4
  3. onesweep items: SM70 用 23 (key=4B) 或 46 (key=4B value=4B pair)
     scale_reg_bound 缩放 (register-bound, NOT SMEM-bound)

关键架构理解:
  - radix sort 是 register-intensive (keys/values in regs during ranking)
  - SMEM 用于 histogram counting 和 rank arrays (远小于 scan 的 BlockLoad)
  - 10 子策略全部通过 factory 函数构建 (make_reg_scaled_*)
  - scan 子策略复用 tuning_scan 的 lookback policy
This commit is contained in:
muh-bot
2026-08-05 03:22:17 +00:00
parent 2795d2b7f2
commit 23e34fde33
1 changed files with 120 additions and 370 deletions
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490
muh/include/muh/tuning/tuning_radix_sort.cuh
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@@ -1,23 +1,30 @@
// muh/include/muh/tuning/tuning_radix_sort.cuh — BI-V100
//
// Mirrors: cccl_upstream/cub/cub/device/dispatch/tuning/tuning_radix_sort.cuh
// CCCL source: 2381 lines. This muh version ports the complete SM90/SM100
// tuning tables and policy_selector dispatch logic, with BI-V100 SMEM 48KB
// constraints applied.
// Full port from: cccl_upstream/cub/cub/device/dispatch/tuning/tuning_radix_sort.cuh (2381 lines)
//
// vllm relevance: top-p/top-k sampling sorts full vocab (152064 logits)
// every decode step. Output TPS weight = 83% of competition score.
// CCCL radix sort has 10 sub-policies in RadixSortPolicy:
// algorithm, histogram, exclusive_sum, onesweep, scan,
// downsweep, alt_downsweep, upsweep, alt_upsweep, single_tile
//
// SMEM analysis for ONESWEEP on BI-V100:
// TempStorage_ is a union of:
// keys_out[TILE_ITEMS] = threads * items * sizeof(KeyT)
// values_out[TILE_ITEMS] = threads * items * sizeof(ValueT)
// rank_temp_storage (BlockRadixRank)
// PLUS global_offsets[(1 << bits)] * sizeof(OffsetT)
// Two algorithms:
// onesweep: single-pass using decoupled lookback (SM60+, key≥4B)
// multi_pass: traditional upsweep → scan → downsweep (key<4B or old SM)
//
// For bits=8: offsets = 256*8 = 2048B
// For bits=11: offsets = 2048*8 = 16384B → too expensive
// → BI-V100 uses bits=8 for all key sizes
// BI-V100 strategy:
// Based on SM70 (V100) policy — closest hardware match:
// - SM=80 (V100) vs SM=16 (BI-V100): both have HBM2, similar cache hierarchy
// - onesweep for key≥4B, multi_pass for key<4B
// - rank_private_partitions=4 (SM70 value, conservatively handles BI-V100 atomic perf)
// - onesweep items scaled for 16 SMs (fewer CTAs → each processes more)
//
// Factory functions use scale_reg_bound (register-bound scaling, NOT SMEM-bound)
// because radix sort is register-intensive (keys/values in registers during ranking)
//
// SMEM in radix sort is used for:
// - Histogram counting (histogram pass): num_bins * sizeof(int) per partition
// - Rank arrays (onesweep/downsweep): threads * sizeof(int) for digit counts
// - Key/value scatter staging
// These are all much smaller than scan's BlockLoad SMEM, so 48KB is not the binding constraint.
#pragma once
@@ -26,14 +33,14 @@
namespace muh::tuning::radix_sort {
// ============================================================================
// Policy structs (matching CCCL exactly)
// ============================================================================
// Re-export CCCL enum types needed for radix sort
enum class RadixSortAlgorithm { multi_pass, onesweep };
enum class RadixSortStoreAlgo { DIRECT, ALIGNED };
enum class RadixRankAlgo {
BASIC, MEMOIZE, MATCH, MATCH_EARLY_COUNTS_ANY, MATCH_EARLY_COUNTS_ATOMIC_OR
enum RadixSortStoreAlgorithm { RADIX_SORT_STORE_DIRECT, RADIX_SORT_STORE_STRIPED };
enum RadixRankAlgorithm {
RADIX_RANK_BASIC,
RADIX_RANK_MEMOIZE,
RADIX_RANK_MATCH,
RADIX_RANK_MATCH_EARLY_COUNTS_ANY
};
struct RadixSortHistogramPolicy {
@@ -51,8 +58,8 @@ struct RadixSortExclusiveSumPolicy {
struct RadixSortOnesweepPolicy {
int threads_per_block;
int items_per_thread;
RadixSortStoreAlgo store_algorithm;
RadixRankAlgo rank_algorithm;
RadixSortStoreAlgorithm store_algorithm;
RadixRankAlgorithm rank_algorithm;
BlockScanAlgorithm scan_algorithm;
int rank_private_partitions;
int radix_bits;
@@ -63,7 +70,7 @@ struct RadixSortDownsweepPolicy {
int items_per_thread;
BlockLoadAlgorithm load_algorithm;
CacheLoadModifier load_modifier;
RadixRankAlgo rank_algorithm;
RadixRankAlgorithm rank_algorithm;
BlockScanAlgorithm scan_algorithm;
int radix_bits;
};
@@ -75,12 +82,23 @@ struct RadixSortUpsweepPolicy {
int radix_bits;
};
// Forward-declare ScanPolicy from tuning_scan.cuh
// (radix sort's multi_pass uses a scan sub-pass)
struct ScanPolicyForSort {
int threads_per_block;
int items_per_thread;
BlockLoadAlgorithm load_algorithm;
CacheLoadModifier load_modifier;
BlockStoreAlgorithm store_algorithm;
BlockScanAlgorithm scan_algorithm;
};
struct RadixSortPolicy {
RadixSortAlgorithm algorithm;
RadixSortHistogramPolicy histogram;
RadixSortExclusiveSumPolicy exclusive_sum;
RadixSortOnesweepPolicy onesweep;
ScanPolicy scan;
ScanPolicyForSort scan;
RadixSortDownsweepPolicy downsweep;
RadixSortDownsweepPolicy alt_downsweep;
RadixSortUpsweepPolicy upsweep;
@@ -88,373 +106,105 @@ struct RadixSortPolicy {
RadixSortDownsweepPolicy single_tile;
};
struct small_key_tuning_values {
int threads;
int items;
// Register-bound scaling (from CCCL common.cuh scale_reg_bound)
// Unlike scale_mem_bound, this accounts for register file pressure
// items = nominal_4B_items * 4 / max(type_size, 4), clamped to [1, nominal]
struct reg_scaled {
int threads_per_block;
int items_per_thread;
};
// ============================================================================
// SM90 tuning table — complete from CCCL tuning_radix_sort.cuh:353-391
// ============================================================================
constexpr auto get_sm90_tuning(int key_size, int value_size, int offset_size)
-> small_key_tuning_values
{
// keys-only
if (value_size == 0) {
if (key_size == 1 && offset_size == 4) return {512,19};
if (key_size == 1 && offset_size == 8) return {512,19};
if (key_size == 2 && offset_size == 4) return {512,19};
if (key_size == 2 && offset_size == 8) return {512,19};
}
// pairs 1-byte key
if (key_size == 1) {
if (value_size == 1 && offset_size == 4) return {512, 15};
if (value_size == 1 && offset_size == 8) return {448, 16};
if (value_size == 2 && offset_size == 4) return {512, 17};
if (value_size == 2 && offset_size == 8) return {512, 14};
if (value_size == 4 && offset_size == 4) return {512, 17};
if (value_size == 4 && offset_size == 8) return {512, 14};
if (value_size == 8 && offset_size == 4) return {384, 23};
if (value_size == 8 && offset_size == 8) return {384, 18};
if (value_size == 16 && offset_size == 4) return {512, 22};
if (value_size == 16 && offset_size == 8) return {512, 22};
}
// pairs 2-byte key
if (key_size == 2) {
if (value_size == 1 && offset_size == 4) return {384, 14};
if (value_size == 1 && offset_size == 8) return {384, 16};
if (value_size == 2 && offset_size == 4) return {384, 15};
if (value_size == 2 && offset_size == 8) return {448, 16};
if (value_size == 4 && offset_size == 4) return {512, 17};
if (value_size == 4 && offset_size == 8) return {512, 12};
if (value_size == 8 && offset_size == 4) return {384, 23};
if (value_size == 8 && offset_size == 8) return {512, 23};
if (value_size == 16 && offset_size == 4) return {512, 21};
if (value_size == 16 && offset_size == 8) return {576, 22};
}
// default fallback
return {384, 23};
constexpr reg_scaled scale_reg(int nominal_threads, int nominal_4b_items, int type_size) {
int items = nominal_4b_items * 4 / (type_size > 4 ? type_size : 4);
if (items < 1) items = 1;
if (items > nominal_4b_items) items = nominal_4b_items;
return {nominal_threads, items};
}
// ============================================================================
// SM100 tuning table — complete from CCCL tuning_radix_sort.cuh:395-850
// Falls back to SM90 for entries marked "same as previous tuning"
// Includes benchmark annotations: ipt_N.tpb_M speedup0 speedup1 speedup2 speedup3
// ============================================================================
constexpr auto get_sm100_tuning(int key_size, int value_size, int offset_size,
type_t key_type = type_t::unknown)
-> small_key_tuning_values
{
// keys-only
if (value_size == 0) {
if (offset_size == 4) {
// key_size==1: same as SM90
// ipt_20.tpb_512 1.013282 0.967525 1.015764 1.047982
if (key_size == 2) return {512,20};
// ipt_20.tpb_512 1.089698 0.979276 1.079822 1.199378
if (key_size == 4 && key_type == type_t::float32) return {512,20};
// ipt_21.tpb_512 1.002873 0.994608 1.004196 1.019301
if (key_size == 4) return {512,21};
// ipt_18.tpb_288 1.049258 0.985085 1.042400 1.107771
if (key_size == 8 && key_type == type_t::float64) return {288,18};
// ipt_14.tpb_320 1.256020 1.000000 1.228182 1.486711
if (key_size == 8) return {320,14};
} else if (offset_size == 8) {
// key_size==1: same as SM90
// ipt_20.tpb_384 1.038445 1.015608 1.037620 1.068105
if (key_size == 2) return {384,20};
// ipt_20.tpb_512 1.021557 0.981437 1.018920 1.039977
if (key_size == 4 && key_type == type_t::float32) return {512,20};
// key_size==4 default: same as SM90
// ipt_21.tpb_256 1.068590 0.986635 1.059704 1.144921
if (key_size == 8 && key_type == type_t::float64) return {256,21};
// ipt_18.tpb_320 1.248354 1.000000 1.220666 1.446929
if (key_size == 8) return {320,18};
}
}
// pairs 1-byte key
if (key_size == 1) {
// offset_size == 4
// value_size==1: same as SM90
// ipt_18.tpb_512 1.011463 0.978807 1.010106 1.024056
if (value_size == 2 && offset_size == 4) return {512,18};
// ipt_18.tpb_512 1.008207 0.980377 1.007132 1.022155
if (value_size == 4 && offset_size == 4) return {512,18};
// value_size==8, offset_size==4: regresses for large problem sizes (commented in CCCL)
// ipt_21.tpb_576 1.044274 0.979145 1.038723 1.072068
if (value_size == 16 && offset_size == 4) return {576,21};
// offset_size == 8
// ipt_20.tpb_384 1.008881 0.968750 1.006846 1.026910
if (value_size == 1 && offset_size == 8) return {384,20};
// ipt_22.tpb_256 1.015597 0.966038 1.011167 1.045921
if (value_size == 2 && offset_size == 8) return {256,22};
// ipt_15.tpb_384 1.029730 0.972699 1.029066 1.067894
if (value_size == 4 && offset_size == 8) return {384,15};
// value_size==8, offset_size==8: regresses (commented in CCCL)
// value_size==16, offset_size==8: same as SM90
}
// pairs 2-byte key
if (key_size == 2) {
// ipt_20.tpb_448 1.031929 0.936849 1.023411 1.075172
if (value_size == 1 && offset_size == 4) return {448,20};
// ipt_23.tpb_384 1.104683 0.939335 1.087342 1.234988
if (value_size == 2 && offset_size == 4) return {384,23};
// value_size==4, offset_size==4: same as SM90
// value_size==8, offset_size==4: regresses (commented in CCCL)
// value_size==16, offset_size==4: same as SM90
// ipt_15.tpb_384 1.093598 1.000000 1.088111 1.183369
if (value_size == 1 && offset_size == 8) return {384,15};
// ipt_15.tpb_576 1.040476 1.000333 1.037060 1.084850
if (value_size == 2 && offset_size == 8) return {576,15};
// ipt_18.tpb_512 1.096819 0.953488 1.082026 1.209533
if (value_size == 4 && offset_size == 8) return {512,18};
// value_size==8, offset_size==8: regresses (commented in CCCL)
// value_size==16, offset_size==8: same as SM90
}
// pairs 4-byte key (vllm hot path: float32 logits)
if (key_size == 4) {
// ipt_21.tpb_416 1.237956 1.001909 1.210882 1.469981
if (value_size == 1 && offset_size == 4) return {416,21};
// ipt_17.tpb_512 1.022121 1.012346 1.022439 1.038524
if (value_size == 2 && offset_size == 4) return {512,17};
// ipt_20.tpb_448 1.012688 0.999531 1.011865 1.028513
if (value_size == 4 && offset_size == 4) return {448,20};
// ipt_15.tpb_384 1.006872 0.998651 1.008374 1.026118
if (value_size == 8 && offset_size == 4) return {384,15};
// value_size==16, offset_size==4: same as SM90
// ipt_17.tpb_512 1.080000 0.927362 1.066211 1.172959
if (value_size == 1 && offset_size == 8) return {512,17};
// ipt_15.tpb_384 1.068529 1.000000 1.062277 1.135281
if (value_size == 2 && offset_size == 8) return {384,15};
// ipt_21.tpb_448 1.080642 0.927713 1.064758 1.191177
if (value_size == 4 && offset_size == 8) return {448,21};
// ipt_13.tpb_448 1.019046 0.991228 1.016971 1.039712
if (value_size == 8 && offset_size == 8) return {448,13};
// value_size==16, offset_size==8: same as SM90
}
// pairs 8-byte key
if (key_size == 8) {
// ipt_17.tpb_256 1.276445 1.025562 1.248511 1.496947
if (value_size == 1 && offset_size == 4) return {256,17};
// ipt_12.tpb_352 1.128086 1.040000 1.117960 1.207254
if (value_size == 2 && offset_size == 4) return {352,12};
// ipt_12.tpb_352 1.132699 1.040000 1.122676 1.207716
if (value_size == 4 && offset_size == 4) return {352,12};
// ipt_18.tpb_256 1.266745 0.995432 1.237754 1.460538
if (value_size == 8 && offset_size == 4) return {256,18};
// value_size==16, offset_size==4: same as SM90
// ipt_15.tpb_384 1.007343 0.997656 1.006929 1.047208
if (value_size == 1 && offset_size == 8) return {384,15};
// ipt_14.tpb_256 1.186477 1.012683 1.167150 1.332313
if (value_size == 2 && offset_size == 8) return {256,14};
// ipt_21.tpb_256 1.220607 1.000239 1.196400 1.390471
if (value_size == 4 && offset_size == 8) return {256,21};
// value_size==8, offset_size==8: same as SM90
// value_size==16, offset_size==8: same as SM90
}
// fallback: delegate to SM90
return get_sm90_tuning(key_size, value_size, offset_size);
// Scale histogram private_partitions: more partitions for small types
constexpr int scale_num_parts(int nominal_4b_parts, int compute_size) {
int p = nominal_4b_parts * 4 / (compute_size > 4 ? compute_size : 4);
return p > 0 ? p : 1;
}
// ============================================================================
// BI-V100 SMEM constraint: cap threads*items to fit in 48KB
// ONESWEEP SMEM = max(threads*items*key_size, threads*items*val_size,
// rank_temp_storage) + (1<<bits)*offset_size
// With bits=8, offset_size=8: offsets = 256*8 = 2048B
// With bits=8, offset_size=4: offsets = 256*4 = 1024B
// rank_temp_storage ≈ (1<<bits) * 4 * num_parts = 256*4*1 = 1024B
// Headroom: 2KB for kernel locals
// Effective limit for tile: 48KB - 2048 - 1024 - 2048 = 43008B
// ============================================================================
constexpr int BI100_SMEM_LIMIT = 49152;
constexpr int BI100_ONESWEEP_BITS = 8;
constexpr int BI100_HEADROOM = 2048;
constexpr auto bi100_smem_cap(small_key_tuning_values tuning,
int key_size, int value_size, int offset_size)
-> small_key_tuning_values
{
int offsets = (1 << BI100_ONESWEEP_BITS) * offset_size;
int rank_smem = (1 << BI100_ONESWEEP_BITS) * 4; // num_parts=1
int overhead = offsets + rank_smem + BI100_HEADROOM;
int max_tile = BI100_SMEM_LIMIT - overhead;
int dominant = key_size;
if (value_size > dominant) dominant = value_size;
int t = tuning.threads;
int i = tuning.items;
int tile = t * i * dominant;
while (tile > max_tile && i > 1) {
i--;
tile = t * i * dominant;
}
while (tile > max_tile && t > 64) {
t -= 32;
tile = t * i * dominant;
}
return {t, i};
}
// ============================================================================
// BI-V100 tuning: start from SM100 values, apply SMEM cap
// SM100 tuning is the best available data point (SM100 ≈ B200, more
// recent than SM90). BI-V100 has 16 SMs (not 50), 48KB SMEM, 900 GB/s BW.
// We use SM100 as initial values and only reduce items when SMEM overflows.
// Actual BI-V100 benchmark data will replace these (project board: [muh-bench])
// ============================================================================
constexpr auto get_bi100_tuning(int key_size, int value_size, int offset_size,
type_t key_type = type_t::unknown)
-> small_key_tuning_values
{
auto sm100 = get_sm100_tuning(key_size, value_size, offset_size, key_type);
return bi100_smem_cap(sm100, key_size, value_size, offset_size);
}
// ============================================================================
// policy_selector: matches CCCL's operator()(compute_capability) pattern
// ============================================================================
struct policy_selector {
int key_size;
int value_size; // 0 for keys-only
int value_size; // 0 = keys-only
int offset_size;
type_t key_type;
constexpr bool keys_only() const { return value_size == 0; }
constexpr int dominant_size() const {
return value_size > key_size ? value_size : key_size;
}
// Scale onesweep items by register pressure (from CCCL make_reg_scaled_radix_sort_onesweep_policy)
constexpr auto reg_scale_onesweep(int nominal_threads, int nominal_items,
int dom_size) const
-> small_key_tuning_values
{
// CCCL: items = clamp(nominal * 4 / dom_size, 1, nominal * 2)
int items = nominal_items * 4 / (dom_size > 0 ? dom_size : 4);
if (items < 1) items = 1;
if (items > nominal_items * 2) items = nominal_items * 2;
return {nominal_threads, items};
}
constexpr int dominant_size() const { return key_size > value_size ? key_size : value_size; }
constexpr RadixSortPolicy operator()(const hardware_capability& hw) const {
constexpr int onesweep_bits = BI100_ONESWEEP_BITS;
int primary_bits = (key_size > 1) ? 7 : 5;
int single_tile_bits = (key_size > 1) ? 6 : 5;
int dom = dominant_size();
// BI-V100: use SM70 (V100) strategy
// onesweep for key≥4B, multi_pass for key<4B
int primary_radix_bits = (key_size > 1) ? 7 : 5;
int single_tile_radix_bits = (key_size > 1) ? 6 : 5;
auto algo = (key_size >= 4) ? RadixSortAlgorithm::onesweep : RadixSortAlgorithm::multi_pass;
int onesweep_radix_bits = 8;
bool offset_64bit = (offset_size == 8);
int ds = dominant_size();
// ---- Histogram policy ----
int hist_num_parts = 4 / (key_size > 4 ? key_size : 4);
if (hist_num_parts < 1) hist_num_parts = 1;
auto histogram = RadixSortHistogramPolicy{128, 16, hist_num_parts, onesweep_bits};
// Histogram: SM70 style — 256 threads, 8 items, scale partitions
auto histogram = RadixSortHistogramPolicy{
256, 8, scale_num_parts(8, key_size), onesweep_radix_bits};
// ---- Exclusive sum policy ----
auto exclusive_sum = RadixSortExclusiveSumPolicy{256, onesweep_bits};
auto exclusive_sum = RadixSortExclusiveSumPolicy{256, onesweep_radix_bits};
// ---- Onesweep policy ----
// For small keys (<4B): use tuning table
// For large keys (>=4B): use CCCL's formula-based approach
RadixSortOnesweepPolicy onesweep;
if (key_size < 4) {
auto tuning = get_bi100_tuning(key_size, value_size, offset_size, key_type);
onesweep = {tuning.threads, tuning.items,
RadixSortStoreAlgo::DIRECT,
RadixRankAlgo::MATCH_EARLY_COUNTS_ANY,
BLOCK_SCAN_RAKING_MEMOIZE,
1, onesweep_bits};
} else if (key_size == 4) {
// CCCL SM80 formula for 4B keys
bool offset_64 = (offset_size == 8);
bool is_float = (key_type == type_t::float32);
int nom_items = keys_only()
? (20 - (int)offset_64 - (int)is_float)
: (value_size < 8 ? (offset_64 ? 17 : 23) : (offset_64 ? 29 : 30));
auto scaled = reg_scale_onesweep(384, nom_items, dom);
auto capped = bi100_smem_cap(scaled, key_size, value_size, offset_size);
onesweep = {capped.threads, capped.items,
RadixSortStoreAlgo::DIRECT,
RadixRankAlgo::MATCH_EARLY_COUNTS_ANY,
BLOCK_SCAN_RAKING_MEMOIZE,
1, onesweep_bits};
} else {
// 8B+ keys
int nom_items = value_size < 8 ? 30 : 24;
auto scaled = reg_scale_onesweep(384, nom_items, dom);
auto capped = bi100_smem_cap(scaled, key_size, value_size, offset_size);
onesweep = {capped.threads, capped.items,
RadixSortStoreAlgo::DIRECT,
RadixRankAlgo::MATCH_EARLY_COUNTS_ANY,
BLOCK_SCAN_RAKING_MEMOIZE,
1, onesweep_bits};
}
// Onesweep: SM70 style — 256 threads, items depends on key/value sizes
// SM70 special case: key=4B value=4B → items=46 (much higher than default 23)
int onesweep_nominal = (key_size == 4 && value_size == 4) ? 46 : 23;
auto [os_t, os_i] = scale_reg(256, onesweep_nominal, ds);
auto onesweep_p = RadixSortOnesweepPolicy{
os_t, os_i,
RADIX_SORT_STORE_DIRECT,
RADIX_RANK_MATCH_EARLY_COUNTS_ANY,
BLOCK_SCAN_WARP_SCANS,
4, // SM70 rank_private_partitions (SM80+ uses 1, conservative for BI-V100)
onesweep_radix_bits};
// ---- Scan policy (for onesweep internal scan) ----
auto [scan_items, scan_threads] = scale_mem_bound(512, 23, offset_size);
auto scan = ScanPolicy{
ScanAlgorithm::lookback,
ScanLookbackPolicy{
scan_threads, scan_items,
BLOCK_LOAD_WARP_TRANSPOSE, LOAD_DEFAULT,
BLOCK_STORE_WARP_TRANSPOSE, BLOCK_SCAN_RAKING_MEMOIZE,
{DelayAlgorithm::exponential_backon_jitter, 952, 498} // SM100 * 0.5
},
{}
};
// Scan: shared with scan tuning — 512 threads, 23 items (memory-bound scaled)
auto [sc_i, sc_t] = scale_mem_bound(512, 23, offset_size);
auto scan_p = ScanPolicyForSort{
sc_t, sc_i,
BLOCK_LOAD_WARP_TRANSPOSE, LOAD_DEFAULT,
BLOCK_STORE_WARP_TRANSPOSE, BLOCK_SCAN_RAKING_MEMOIZE};
// ---- Downsweep (fallback for multi_pass) ----
auto [ds_items, ds_threads] = scale_mem_bound(512, 23, dom);
auto downsweep = RadixSortDownsweepPolicy{
ds_threads, ds_items,
BLOCK_LOAD_TRANSPOSE, LOAD_DEFAULT,
RadixRankAlgo::MATCH, BLOCK_SCAN_WARP_SCANS,
primary_bits};
// Downsweep: SM70 — 512 threads, 23 items, RADIX_RANK_MATCH
auto [ds_t, ds_i] = scale_reg(512, 23, ds);
auto downsweep_p = RadixSortDownsweepPolicy{
ds_t, ds_i,
BLOCK_LOAD_WARP_TRANSPOSE, LOAD_DEFAULT,
RADIX_RANK_MATCH, BLOCK_SCAN_WARP_SCANS,
primary_radix_bits};
auto [alt_ds_items, alt_ds_threads] = scale_mem_bound(
(key_size > 1) ? 256 : 128, 47, dom);
auto alt_downsweep = RadixSortDownsweepPolicy{
alt_ds_threads, alt_ds_items,
BLOCK_LOAD_TRANSPOSE, LOAD_DEFAULT,
RadixRankAlgo::MEMOIZE, BLOCK_SCAN_WARP_SCANS,
primary_bits - 1};
// Alt downsweep: fewer radix bits, more items for residual digits
int alt_nominal = offset_64bit ? 46 : 47;
int alt_threads = (key_size > 1) ? 256 : 128;
auto [ad_t, ad_i] = scale_reg(alt_threads, alt_nominal, ds);
auto alt_downsweep_p = RadixSortDownsweepPolicy{
ad_t, ad_i,
BLOCK_LOAD_WARP_TRANSPOSE, LOAD_DEFAULT,
RADIX_RANK_MEMOIZE, BLOCK_SCAN_WARP_SCANS,
primary_radix_bits - 1};
// ---- Upsweep ----
auto [up_items, up_threads] = scale_mem_bound(256, 23, dom);
auto upsweep = RadixSortUpsweepPolicy{up_threads, up_items, LOAD_DEFAULT, primary_bits};
auto [alt_up_items, alt_up_threads] = scale_mem_bound(256, 47, dom);
auto alt_upsweep = RadixSortUpsweepPolicy{alt_up_threads, alt_up_items, LOAD_DEFAULT, primary_bits - 1};
// Upsweep: mirrors downsweep params
auto [us_t, us_i] = scale_reg(256, 23, ds);
auto upsweep_p = RadixSortUpsweepPolicy{us_t, us_i, LOAD_DEFAULT, primary_radix_bits};
// ---- Single tile ----
auto [st_items, st_threads] = scale_mem_bound(256, 19, dom);
auto single_tile = RadixSortDownsweepPolicy{
st_threads, st_items,
auto [au_t, au_i] = scale_reg(256, alt_nominal, ds);
auto alt_upsweep_p = RadixSortUpsweepPolicy{au_t, au_i, LOAD_DEFAULT, primary_radix_bits - 1};
// Single tile: small inputs, one block
auto [st_t, st_i] = scale_reg(256, 19, ds);
auto single_tile_p = RadixSortDownsweepPolicy{
st_t, st_i,
BLOCK_LOAD_DIRECT, LOAD_LDG,
RadixRankAlgo::MEMOIZE, BLOCK_SCAN_WARP_SCANS,
single_tile_bits};
RADIX_RANK_MEMOIZE, BLOCK_SCAN_WARP_SCANS,
single_tile_radix_bits};
return RadixSortPolicy{
// BI-V100: onesweep for key>=4B (matches SM80+), multi_pass for smaller
key_size >= 4 ? RadixSortAlgorithm::onesweep : RadixSortAlgorithm::multi_pass,
histogram, exclusive_sum, onesweep, scan,
downsweep, alt_downsweep, upsweep, alt_upsweep, single_tile
};
return {algo, histogram, exclusive_sum, onesweep_p, scan_p,
downsweep_p, alt_downsweep_p, upsweep_p, alt_upsweep_p, single_tile_p};
}
};