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fix simd accumulator overflow #1

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merged 3 commits into from
Jul 16, 2023
Merged

fix simd accumulator overflow #1

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180dd5a
fix simd accumulator overflow
PeterFaiman Jul 15, 2023
189fe90
fix chunked overflow
PeterFaiman Jul 15, 2023
bf23c93
flush simd accumulator every 128 iterations
PeterFaiman Jul 15, 2023
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15 changes: 11 additions & 4 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ pub fn opt4_simd(input: &str) -> i64 {
let input_v = vld1q_u8(input[block_i * N_LANES..].as_ptr());
let eq_s_v = vandq_u8(input_v, one_v);
acc_v = vaddq_u8(acc_v, eq_s_v);
if block_i % (u8::MAX as usize + 1) == u8::MAX as usize {
if block_i % 128 == 127 {
res += vaddlvq_u8(acc_v) as i64;
acc_v = vmovq_n_u8(0);
}
Expand Down Expand Up @@ -92,7 +92,7 @@ macro_rules! simd_unrolled {
let v_eq_s~I= vandq_u8(v_input~I, one_v);
v_acc~I = vaddq_u8(v_acc~I, v_eq_s~I);
});
if block_i % (u8::MAX as usize + 1) == u8::MAX as usize {
if block_i % 128 == 127 {
seq!(I in 0..$unroll_factor {
res += vaddlvq_u8(v_acc~I) as i64;
v_acc~I = vmovq_n_u8(0);
Expand Down Expand Up @@ -121,7 +121,7 @@ simd_unrolled!(opt5_simd_unrolled_16x, 16);
pub fn opt6_chunk_count(input: &str) -> i64 {
let n_s = input
.as_bytes()
.chunks(256)
.chunks(192)
.map(|chunk| chunk.iter().map(|&b| b & 1).sum::<u8>())
.map(|chunk_total| chunk_total as i64)
.sum::<i64>();
Expand All @@ -131,7 +131,7 @@ pub fn opt6_chunk_count(input: &str) -> i64 {
/// Credit to u/Sharlinator
/// https://www.reddit.com/r/rust/comments/14yvlc9/comment/jrwt29t
pub fn opt6_chunk_exact_count(input: &str) -> i64 {
let iter = input.as_bytes().chunks_exact(256);
let iter = input.as_bytes().chunks_exact(192);
let rest = iter.remainder();
let mut n_s = iter
.map(|chunk| chunk.iter().map(|&b| b & 1).sum::<u8>())
Expand Down Expand Up @@ -187,4 +187,11 @@ mod tests {
let expected = baseline_unicode(&input);
assert_eq_all!(expected, &input);
}

#[test]
fn test_all_s() {
let expected = 1024 * 1024;
let input = "s".repeat(expected);
assert_eq_all!(expected as i64, &input);
}
}