1 // Copyright ©2016 The Gonum Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // +build !noasm,!appengine
9 // func L1Norm(x []float64) float64
10 TEXT ·L1Norm(SB), NOSPLIT, $0
11 MOVQ x_base+0(FP), SI // SI = &x
12 MOVQ x_len+8(FP), CX // CX = len(x)
14 PXOR X0, X0 // p_sum_i = 0
22 CMPQ CX, $0 // if CX == 0 { return 0 }
25 ANDQ $7, BX // BX = len(x) % 8
26 SHRQ $3, CX // CX = floor( len(x) / 8 )
27 JZ absum_tail_start // if CX == 0 { goto absum_tail_start }
30 // p_sum += max( p_sum + x[i], p_sum - x[i] )
31 MOVUPS (SI)(AX*8), X8 // X_i = x[i:i+1]
32 MOVUPS 16(SI)(AX*8), X9
33 MOVUPS 32(SI)(AX*8), X10
34 MOVUPS 48(SI)(AX*8), X11
35 ADDPD X8, X0 // p_sum_i += X_i ( positive values )
39 SUBPD X8, X1 // p_sum_(i+1) -= X_i ( negative values )
43 MAXPD X1, X0 // p_sum_i = max( p_sum_i, p_sum_(i+1) )
47 MOVAPS X0, X1 // p_sum_(i+1) = p_sum_i
52 LOOP absum_loop // } while --CX > 0
54 // p_sum_0 = \sum_{i=1}^{3}( p_sum_(i*2) )
59 // p_sum_0[0] = p_sum_0[0] + p_sum_0[1]
61 SHUFPD $0x3, X0, X0 // lower( p_sum_0 ) = upper( p_sum_0 )
64 JE absum_end // if BX == 0 { goto absum_end }
66 absum_tail_start: // Reset loop registers
67 MOVQ BX, CX // Loop counter: CX = BX
68 XORPS X8, X8 // X_8 = 0
71 // p_sum += max( p_sum + x[i], p_sum - x[i] )
72 MOVSD (SI)(AX*8), X8 // X_8 = x[i]
73 MOVSD X0, X1 // p_sum_1 = p_sum_0
74 ADDSD X8, X0 // p_sum_0 += X_8
75 SUBSD X8, X1 // p_sum_1 -= X_8
76 MAXSD X1, X0 // p_sum_0 = max( p_sum_0, p_sum_1 )
78 LOOP absum_tail // } while --CX > 0
80 absum_end: // return p_sum_0