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Simplify ForDeltaUtil's prefix sum. #14979

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Merged
jpountz merged 1 commit into from
Jul 23, 2025
Merged

Simplify ForDeltaUtil's prefix sum. #14979

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4 changes: 2 additions & 2 deletions lucene/core/src/generated/checksums/generateForDeltaUtil.json
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
{
"lucene/core/src/java/org/apache/lucene/codecs/lucene103/ForDeltaUtil.java": "dc896d5df4b2a091918bfa14b30aad417feaffac",
"lucene/core/src/java/org/apache/lucene/codecs/lucene103/gen_ForDeltaUtil.py": "d622cc9f9a13987a07c2472a1c5b0111a3a7bc62"
"lucene/core/src/java/org/apache/lucene/codecs/lucene103/ForDeltaUtil.java": "7e14917412c0f4e29453c5b604bf4dddf08d40d1",
"lucene/core/src/java/org/apache/lucene/codecs/lucene103/gen_ForDeltaUtil.py": "82845dcc4b25af1b944bffcaf44d1fdf53e126a0"
}
115 changes: 9 additions & 106 deletions lucene/core/src/java/org/apache/lucene/codecs/lucene103/ForDeltaUtil.java
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ private static void prefixSum8(int[] arr, int base) {
// When the number of bits per value is 4 or less, we can sum up all values in a block without
// risking overflowing an 8-bits integer. This allows computing the prefix sum by summing up 4
// values at once.
innerPrefixSum8(arr);
prefixSum(arr, ONE_BLOCK_SIZE_FOURTH, 0);
expand8(arr);
final int l0 = base;
final int l1 = l0 + arr[ONE_BLOCK_SIZE_FOURTH - 1];
Expand All @@ -94,7 +94,7 @@ private static void prefixSum16(int[] arr, int base) {
// When the number of bits per value is 11 or less, we can sum up all values in a block without
// risking overflowing an 16-bits integer. This allows computing the prefix sum by summing up 2
// values at once.
innerPrefixSum16(arr);
prefixSum(arr, HALF_BLOCK_SIZE, 0);
expand16(arr);
final int l0 = base;
final int l1 = base + arr[HALF_BLOCK_SIZE - 1];
Expand All @@ -105,112 +105,15 @@ private static void prefixSum16(int[] arr, int base) {
}

private static void prefixSum32(int[] arr, int base) {
arr[0] += base;
for (int i = 1; i < BLOCK_SIZE; ++i) {
arr[i] += arr[i - 1];
}
}

// For some reason unrolling seems to help
private static void innerPrefixSum8(int[] arr) {
arr[1] += arr[0];
arr[2] += arr[1];
arr[3] += arr[2];
arr[4] += arr[3];
arr[5] += arr[4];
arr[6] += arr[5];
arr[7] += arr[6];
arr[8] += arr[7];
arr[9] += arr[8];
arr[10] += arr[9];
arr[11] += arr[10];
arr[12] += arr[11];
arr[13] += arr[12];
arr[14] += arr[13];
arr[15] += arr[14];
arr[16] += arr[15];
arr[17] += arr[16];
arr[18] += arr[17];
arr[19] += arr[18];
arr[20] += arr[19];
arr[21] += arr[20];
arr[22] += arr[21];
arr[23] += arr[22];
arr[24] += arr[23];
arr[25] += arr[24];
arr[26] += arr[25];
arr[27] += arr[26];
arr[28] += arr[27];
arr[29] += arr[28];
arr[30] += arr[29];
arr[31] += arr[30];
prefixSum(arr, BLOCK_SIZE, base);
}

// For some reason unrolling seems to help
private static void innerPrefixSum16(int[] arr) {
arr[1] += arr[0];
arr[2] += arr[1];
arr[3] += arr[2];
arr[4] += arr[3];
arr[5] += arr[4];
arr[6] += arr[5];
arr[7] += arr[6];
arr[8] += arr[7];
arr[9] += arr[8];
arr[10] += arr[9];
arr[11] += arr[10];
arr[12] += arr[11];
arr[13] += arr[12];
arr[14] += arr[13];
arr[15] += arr[14];
arr[16] += arr[15];
arr[17] += arr[16];
arr[18] += arr[17];
arr[19] += arr[18];
arr[20] += arr[19];
arr[21] += arr[20];
arr[22] += arr[21];
arr[23] += arr[22];
arr[24] += arr[23];
arr[25] += arr[24];
arr[26] += arr[25];
arr[27] += arr[26];
arr[28] += arr[27];
arr[29] += arr[28];
arr[30] += arr[29];
arr[31] += arr[30];
arr[32] += arr[31];
arr[33] += arr[32];
arr[34] += arr[33];
arr[35] += arr[34];
arr[36] += arr[35];
arr[37] += arr[36];
arr[38] += arr[37];
arr[39] += arr[38];
arr[40] += arr[39];
arr[41] += arr[40];
arr[42] += arr[41];
arr[43] += arr[42];
arr[44] += arr[43];
arr[45] += arr[44];
arr[46] += arr[45];
arr[47] += arr[46];
arr[48] += arr[47];
arr[49] += arr[48];
arr[50] += arr[49];
arr[51] += arr[50];
arr[52] += arr[51];
arr[53] += arr[52];
arr[54] += arr[53];
arr[55] += arr[54];
arr[56] += arr[55];
arr[57] += arr[56];
arr[58] += arr[57];
arr[59] += arr[58];
arr[60] += arr[59];
arr[61] += arr[60];
arr[62] += arr[61];
arr[63] += arr[62];
private static void prefixSum(int[] arr, int len, int base) {
int sum = base;
for (int i = 0; i < len; ++i) {
sum += arr[i];
arr[i] = sum;
}
}

private final int[] tmp = new int[BLOCK_SIZE];
Expand Down
115 changes: 9 additions & 106 deletions lucene/core/src/java/org/apache/lucene/codecs/lucene103/gen_ForDeltaUtil.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -101,7 +101,7 @@
// When the number of bits per value is 4 or less, we can sum up all values in a block without
// risking overflowing an 8-bits integer. This allows computing the prefix sum by summing up 4
// values at once.
innerPrefixSum8(arr);
prefixSum(arr, ONE_BLOCK_SIZE_FOURTH, 0);
expand8(arr);
final int l0 = base;
final int l1 = l0 + arr[ONE_BLOCK_SIZE_FOURTH - 1];
Expand All @@ -120,7 +120,7 @@
// When the number of bits per value is 11 or less, we can sum up all values in a block without
// risking overflowing an 16-bits integer. This allows computing the prefix sum by summing up 2
// values at once.
innerPrefixSum16(arr);
prefixSum(arr, HALF_BLOCK_SIZE, 0);
expand16(arr);
final int l0 = base;
final int l1 = base + arr[HALF_BLOCK_SIZE - 1];
Expand All @@ -131,112 +131,15 @@
}

private static void prefixSum32(int[] arr, int base) {
arr[0] += base;
for (int i = 1; i < BLOCK_SIZE; ++i) {
arr[i] += arr[i-1];
}
}

// For some reason unrolling seems to help
private static void innerPrefixSum8(int[] arr) {
arr[1] += arr[0];
arr[2] += arr[1];
arr[3] += arr[2];
arr[4] += arr[3];
arr[5] += arr[4];
arr[6] += arr[5];
arr[7] += arr[6];
arr[8] += arr[7];
arr[9] += arr[8];
arr[10] += arr[9];
arr[11] += arr[10];
arr[12] += arr[11];
arr[13] += arr[12];
arr[14] += arr[13];
arr[15] += arr[14];
arr[16] += arr[15];
arr[17] += arr[16];
arr[18] += arr[17];
arr[19] += arr[18];
arr[20] += arr[19];
arr[21] += arr[20];
arr[22] += arr[21];
arr[23] += arr[22];
arr[24] += arr[23];
arr[25] += arr[24];
arr[26] += arr[25];
arr[27] += arr[26];
arr[28] += arr[27];
arr[29] += arr[28];
arr[30] += arr[29];
arr[31] += arr[30];
prefixSum(arr, BLOCK_SIZE, base);
}

// For some reason unrolling seems to help
private static void innerPrefixSum16(int[] arr) {
arr[1] += arr[0];
arr[2] += arr[1];
arr[3] += arr[2];
arr[4] += arr[3];
arr[5] += arr[4];
arr[6] += arr[5];
arr[7] += arr[6];
arr[8] += arr[7];
arr[9] += arr[8];
arr[10] += arr[9];
arr[11] += arr[10];
arr[12] += arr[11];
arr[13] += arr[12];
arr[14] += arr[13];
arr[15] += arr[14];
arr[16] += arr[15];
arr[17] += arr[16];
arr[18] += arr[17];
arr[19] += arr[18];
arr[20] += arr[19];
arr[21] += arr[20];
arr[22] += arr[21];
arr[23] += arr[22];
arr[24] += arr[23];
arr[25] += arr[24];
arr[26] += arr[25];
arr[27] += arr[26];
arr[28] += arr[27];
arr[29] += arr[28];
arr[30] += arr[29];
arr[31] += arr[30];
arr[32] += arr[31];
arr[33] += arr[32];
arr[34] += arr[33];
arr[35] += arr[34];
arr[36] += arr[35];
arr[37] += arr[36];
arr[38] += arr[37];
arr[39] += arr[38];
arr[40] += arr[39];
arr[41] += arr[40];
arr[42] += arr[41];
arr[43] += arr[42];
arr[44] += arr[43];
arr[45] += arr[44];
arr[46] += arr[45];
arr[47] += arr[46];
arr[48] += arr[47];
arr[49] += arr[48];
arr[50] += arr[49];
arr[51] += arr[50];
arr[52] += arr[51];
arr[53] += arr[52];
arr[54] += arr[53];
arr[55] += arr[54];
arr[56] += arr[55];
arr[57] += arr[56];
arr[58] += arr[57];
arr[59] += arr[58];
arr[60] += arr[59];
arr[61] += arr[60];
arr[62] += arr[61];
arr[63] += arr[62];
private static void prefixSum(int[] arr, int len, int base) {
int sum = base;
for (int i = 0; i < len; ++i) {
sum += arr[i];
arr[i] = sum;
}
}

private final int[] tmp = new int[BLOCK_SIZE];
Expand Down
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