mirror of
https://github.com/metabarcoding/obitools4.git
synced 2026-11-09 09:24:41 +00:00
Eric Coissac
75bb635a6c
Introduces the BandedLCS function for efficient LCS scoring, supporting both scalar and SIMD implementations. Adds comprehensive unit tests, benchmarking utilities, and error handling for sequence constraints.
108 lines
2.8 KiB
Go
108 lines
2.8 KiB
Go
//go:build goexperiment.simd
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package obialign
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import "simd"
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const haveSIMD = true
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func simdLanes() int {
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var probe simd.Uint32s
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return probe.Len()
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}
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// encodeIUPAC writes in dst the 4-bit IUPAC mask of each base of s, reversed
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// if rev is set, followed by zero padding up to len(dst).
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func encodeIUPAC(dst []uint32, s []byte, rev bool) {
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n := len(s)
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for x := range dst {
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dst[x] = 0
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}
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if rev {
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for x, c := range s {
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dst[n-1-x] = uint32(iupacMask[c])
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}
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return
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}
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for x, c := range s {
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dst[x] = uint32(iupacMask[c])
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}
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}
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// encodeBases encodes both sequences once for all the passes of an alignment.
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func encodeBases(ws *bandedLCSWorkspace, a, b []byte) {
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vl := simdLanes()
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ws.aRev = growUint32(ws.aRev, len(a)+vl)
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ws.bCode = growUint32(ws.bCode, len(b)+vl)
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encodeIUPAC(ws.aRev, a, true)
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encodeIUPAC(ws.bCode, b, false)
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}
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// bandedLCSSIMD runs the banded DP along antidiagonals t = i + j. Lane i of
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// the buffer of antidiagonal t holds the cell (i, t-i), so that
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//
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// diag = buffer[t-2][i-1] up = buffer[t-1][i-1] left = buffer[t-1][i]
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//
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// are plain unaligned loads. Along an antidiagonal the offset j-i = t-2i
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// must stay in [kmin, kmax], which gives the window [lo, hi] of rows. The
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// vector loop may run past hi; the lanes beyond are then reset to 0
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// (unavailable), as is the lane just before the window, because the next
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// antidiagonals read them as neighbours. Lane 0 and lane t carry the first
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// row and the first column of the matrix.
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//
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// Requires encodeBases to have been called, lA >= lB >= 1 and kmin <= 0 <=
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// kmax.
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func bandedLCSSIMD(lA, lB, kmin, kmax int, ws *bandedLCSWorkspace) uint32 {
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vl := simdLanes()
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aRev, bCode := ws.aRev, ws.bCode
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size := lB + 2*vl + 2
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for r := range ws.rows {
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ws.rows[r] = growUint32(ws.rows[r], size)
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clear(ws.rows[r])
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}
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p2, p1, cur := ws.rows[0], ws.rows[1], ws.rows[2]
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p2[0] = lcsLenBase // cell (0,0)
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if kmax >= 1 {
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p1[0] = lcsLenBase - 1 // cell (0,1)
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}
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if kmin <= -1 {
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p1[1] = lcsLenBase - 1 // cell (1,0)
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}
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zero := simd.BroadcastUint32s(0)
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one := simd.BroadcastUint32s(1)
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unit := simd.BroadcastUint32s(lcsScoreUnit)
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for t := 2; t <= lA+lB; t++ {
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lo := max(1, t-lA, (t-kmax+1)>>1)
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hi := min(lB, t-1, (t-kmin)>>1)
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for i := lo; i <= hi; i += vl {
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ca := simd.LoadUint32s(aRev[lA-t+i:])
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cb := simd.LoadUint32s(bCode[i-1:])
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inc := unit.Masked(ca.And(cb).NotEqual(zero))
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d := simd.LoadUint32s(p2[i-1:]).Add(inc)
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u := simd.LoadUint32s(p1[i-1:])
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l := simd.LoadUint32s(p1[i:])
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d.Max(u).Max(l).Sub(one).Store(cur[i:])
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}
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zero.Store(cur[hi+1:])
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if lo > 1 {
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cur[lo-1] = 0
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}
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cur[0] = 0
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if t <= lA && t <= kmax {
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cur[0] = lcsLenBase - uint32(t)
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}
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if t <= lB && -t >= kmin {
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cur[t] = lcsLenBase - uint32(t)
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}
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p2, p1, cur = p1, cur, p2
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}
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return p1[lB]
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}
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