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tpxb: 16-wide manual unroll - but it does not seem to be faster

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This commit is contained in:
Richard Thier 2025-10-01 04:02:08 +02:00
parent 036725611b
commit 6d79461262
2 changed files with 166 additions and 26 deletions
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188
threepass_xbit.h
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@ -20,6 +20,13 @@ static inline constexpr uint32_t min3u32_xb(uint32_t a, uint32_t b, uint32_t c)
((b <= c) ? b : c); ((b <= c) ? b : c);
} }
static inline void tpxb_process_element(uint32_t num, uint32_t* arr, uint32_t* bucket,
uint32_t shr, uint32_t mask) {
auto bkeyni = (num >> shr) & mask;
auto offset = --bucket[bkeyni];
arr[offset] = num;
}
/** /**
* Simple three-pass (ok: 3 + 1) bottom-up internal radix sort writter for thiersort3 * Simple three-pass (ok: 3 + 1) bottom-up internal radix sort writter for thiersort3
* *
@ -91,44 +98,177 @@ static inline void threepass_xb(uint32_t *a, uint32_t *buf, int n) noexcept {
// Bottom digit a->buf // Bottom digit a->buf
// right-to-left to ensure already sorted digits order we keep for iterations // right-to-left to ensure already sorted digits order we keep for iterations
#pragma GCC unroll 48 #pragma GCC unroll 3
for(uint32_t i = n; i > 0; --i) { for(i = n; i >= 16; i -= 16) {
// Prefetch caches // Prefetch the NEXT block (not current) at optimal distance
//__builtin_prefetch(&a[i-8]); if (i > 17) { // Ensure we don't prefetch out of bounds
// Get num and its new offset / location __builtin_prefetch(&a[i - 17]);
auto num = a[i - 1]; }
if (i > 17*2) { // Ensure we don't prefetch out of bounds
__builtin_prefetch(&a[i - 17*2]);
}
if (i > 17*3) { // Ensure we don't prefetch out of bounds
__builtin_prefetch(&a[i - 17*3]);
}
// Process 16 elements in reverse order
auto num15 = a[i - 1];
auto num14 = a[i - 2];
auto num13 = a[i - 3];
auto num12 = a[i - 4];
auto num11 = a[i - 5];
auto num10 = a[i - 6];
auto num9 = a[i - 7];
auto num8 = a[i - 8];
auto num7 = a[i - 9];
auto num6 = a[i - 10];
auto num5 = a[i - 11];
auto num4 = a[i - 12];
auto num3 = a[i - 13];
auto num2 = a[i - 14];
auto num1 = a[i - 15];
auto num0 = a[i - 16];
// Process all 16 elements (your bucket logic here)
tpxb_process_element(num15, buf, bucket3, shr3, mask3);
tpxb_process_element(num14, buf, bucket3, shr3, mask3);
tpxb_process_element(num13, buf, bucket3, shr3, mask3);
tpxb_process_element(num12, buf, bucket3, shr3, mask3);
tpxb_process_element(num11, buf, bucket3, shr3, mask3);
tpxb_process_element(num10, buf, bucket3, shr3, mask3);
tpxb_process_element(num9, buf, bucket3, shr3, mask3);
tpxb_process_element(num8, buf, bucket3, shr3, mask3);
tpxb_process_element(num7, buf, bucket3, shr3, mask3);
tpxb_process_element(num6, buf, bucket3, shr3, mask3);
tpxb_process_element(num5, buf, bucket3, shr3, mask3);
tpxb_process_element(num4, buf, bucket3, shr3, mask3);
tpxb_process_element(num3, buf, bucket3, shr3, mask3);
tpxb_process_element(num2, buf, bucket3, shr3, mask3);
tpxb_process_element(num1, buf, bucket3, shr3, mask3);
tpxb_process_element(num0, buf, bucket3, shr3, mask3);
}
// Handle remainder (less than 16 elements)
for(uint32_t j = i; j > 0; --j) {
auto num = a[j - 1];
auto bkeyni = (num >> shr3) & mask3; auto bkeyni = (num >> shr3) & mask3;
auto offset = --bucket3[bkeyni]; auto offset = --bucket3[bkeyni];
// Add to the proper target location
buf[offset] = num; buf[offset] = num;
} }
// Mid digit buf->a // Mid digit buf->a
// right-to-left to ensure already sorted digits order we keep for iterations // right-to-left to ensure already sorted digits order we keep for iterations
#pragma GCC unroll 48 #pragma GCC unroll 3
for(uint32_t i = n; i > 0; --i) { for(i = n; i >= 16; i -= 16) {
// Prefetch caches // Prefetch the NEXT block (not current) at optimal distance
//__builtin_prefetch(&buf[i-8]); if (i > 17) { // Ensure we don't prefetch out of bounds
// Get num and its new offset / location __builtin_prefetch(&buf[i - 17]);
auto num = buf[i - 1]; }
if (i > 17*2) { // Ensure we don't prefetch out of bounds
__builtin_prefetch(&buf[i - 17*2]);
}
if (i > 17*3) { // Ensure we don't prefetch out of bounds
__builtin_prefetch(&buf[i - 17*3]);
}
// Process 16 elements in reverse order
auto num15 = buf[i - 1];
auto num14 = buf[i - 2];
auto num13 = buf[i - 3];
auto num12 = buf[i - 4];
auto num11 = buf[i - 5];
auto num10 = buf[i - 6];
auto num9 = buf[i - 7];
auto num8 = buf[i - 8];
auto num7 = buf[i - 9];
auto num6 = buf[i - 10];
auto num5 = buf[i - 11];
auto num4 = buf[i - 12];
auto num3 = buf[i - 13];
auto num2 = buf[i - 14];
auto num1 = buf[i - 15];
auto num0 = buf[i - 16];
// Process all 16 elements (your bucket logic here)
tpxb_process_element(num15, a, bucket2, shr2, mask2);
tpxb_process_element(num14, a, bucket2, shr2, mask2);
tpxb_process_element(num13, a, bucket2, shr2, mask2);
tpxb_process_element(num12, a, bucket2, shr2, mask2);
tpxb_process_element(num11, a, bucket2, shr2, mask2);
tpxb_process_element(num10, a, bucket2, shr2, mask2);
tpxb_process_element(num9, a, bucket2, shr2, mask2);
tpxb_process_element(num8, a, bucket2, shr2, mask2);
tpxb_process_element(num7, a, bucket2, shr2, mask2);
tpxb_process_element(num6, a, bucket2, shr2, mask2);
tpxb_process_element(num5, a, bucket2, shr2, mask2);
tpxb_process_element(num4, a, bucket2, shr2, mask2);
tpxb_process_element(num3, a, bucket2, shr2, mask2);
tpxb_process_element(num2, a, bucket2, shr2, mask2);
tpxb_process_element(num1, a, bucket2, shr2, mask2);
tpxb_process_element(num0, a, bucket2, shr2, mask2);
}
// Handle remainder (less than 16 elements)
for(uint32_t j = i; j > 0; --j) {
auto num = buf[j - 1];
auto bkeyni = (num >> shr2) & mask2; auto bkeyni = (num >> shr2) & mask2;
auto offset = --bucket2[bkeyni]; auto offset = --bucket2[bkeyni];
// Add to the proper target location
a[offset] = num; a[offset] = num;
} }
// Top digit a->buf // Top digit a->buf
// right-to-left to ensure already sorted digits order we keep for iterations // right-to-left to ensure already sorted digits order we keep for iterations
#pragma GCC unroll 48 #pragma GCC unroll 3
for(uint32_t i = n; i > 0; --i) { for(i = n; i >= 16; i -= 16) {
// Prefetch caches // Prefetch the NEXT block (not current) at optimal distance
// __builtin_prefetch(&a[i-16]); if (i > 17) { // Ensure we don't prefetch out of bounds
// Get num and its new offset / location __builtin_prefetch(&a[i - 17]);
auto num = a[i - 1]; }
if (i > 17*2) { // Ensure we don't prefetch out of bounds
__builtin_prefetch(&a[i - 17*2]);
}
if (i > 17*3) { // Ensure we don't prefetch out of bounds
__builtin_prefetch(&a[i - 17*3]);
}
// Process 16 elements in reverse order
auto num15 = a[i - 1];
auto num14 = a[i - 2];
auto num13 = a[i - 3];
auto num12 = a[i - 4];
auto num11 = a[i - 5];
auto num10 = a[i - 6];
auto num9 = a[i - 7];
auto num8 = a[i - 8];
auto num7 = a[i - 9];
auto num6 = a[i - 10];
auto num5 = a[i - 11];
auto num4 = a[i - 12];
auto num3 = a[i - 13];
auto num2 = a[i - 14];
auto num1 = a[i - 15];
auto num0 = a[i - 16];
// Process all 16 elements (your bucket logic here)
tpxb_process_element(num15, buf, bucket1, shr1, mask1);
tpxb_process_element(num14, buf, bucket1, shr1, mask1);
tpxb_process_element(num13, buf, bucket1, shr1, mask1);
tpxb_process_element(num12, buf, bucket1, shr1, mask1);
tpxb_process_element(num11, buf, bucket1, shr1, mask1);
tpxb_process_element(num10, buf, bucket1, shr1, mask1);
tpxb_process_element(num9, buf, bucket1, shr1, mask1);
tpxb_process_element(num8, buf, bucket1, shr1, mask1);
tpxb_process_element(num7, buf, bucket1, shr1, mask1);
tpxb_process_element(num6, buf, bucket1, shr1, mask1);
tpxb_process_element(num5, buf, bucket1, shr1, mask1);
tpxb_process_element(num4, buf, bucket1, shr1, mask1);
tpxb_process_element(num3, buf, bucket1, shr1, mask1);
tpxb_process_element(num2, buf, bucket1, shr1, mask1);
tpxb_process_element(num1, buf, bucket1, shr1, mask1);
tpxb_process_element(num0, buf, bucket1, shr1, mask1);
}
// Handle remainder (less than 16 elements)
for(uint32_t j = i; j > 0; --j) {
auto num = a[j - 1];
auto bkeyni = (num >> shr1) & mask1; auto bkeyni = (num >> shr1) & mask1;
auto offset = --bucket1[bkeyni]; auto offset = --bucket1[bkeyni];
// Add to the proper target location
buf[offset] = num; buf[offset] = num;
} }
} }

4
ypsu.cpp
View File

@ -895,8 +895,8 @@ int main(int argc, char **argv) {
printf("Sorting %d elements:\n\n", n); printf("Sorting %d elements:\n\n", n);
// Uncomment this for profiling and alg! // Uncomment this for profiling and alg!
measure_single(n); // measure_single(n);
return 0; // return 0;
for (auto inputtype : inputtypes) { for (auto inputtype : inputtypes) {
printf("%10s", inputtype.c_str()); printf("%10s", inputtype.c_str());