qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-23 16:10:05 -07:00
Code Releases Activity

math/big: reduce amount of copying in Montgomery multiplication

Browse Source 
Instead shifting the accumulator every iteration of the loop, shift
once in the end. This significantly improves performance on arm64.

On arm64:

name                  old time/op    new time/op    delta
RSA2048Decrypt          3.33ms ± 0%    2.63ms ± 0%  -20.94%  (p=0.000 n=11+11)
RSA2048Sign             4.22ms ± 0%    3.55ms ± 0%  -15.89%  (p=0.000 n=11+11)
3PrimeRSA2048Decrypt    1.95ms ± 0%    1.59ms ± 0%  -18.59%  (p=0.000 n=11+11)

On Skylake:

name                    old time/op  new time/op  delta
RSA2048Decrypt-8        1.73ms ± 2%  1.55ms ± 2%  -10.19%  (p=0.000 n=10+10)
RSA2048Sign-8           2.17ms ± 2%  2.00ms ± 2%   -7.93%  (p=0.000 n=10+10)
3PrimeRSA2048Decrypt-8  1.10ms ± 2%  0.96ms ± 2%  -13.03%  (p=0.000 n=10+9)

Change-Id: I5786191a1a09e4217fdb1acfd90880d35c5855f7
Reviewed-on: https://go-review.googlesource.com/99838
Run-TryBot: Vlad Krasnov <vlad@cloudflare.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
This commit is contained in:
Vlad Krasnov 2018-03-09 17:14:49 +00:00 committed by Robert Griesemer
parent 4b837c7023
commit 26d74e8b65
1 changed files with 9 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
src/math/big/nat.go
View File

@ -213,18 +213,17 @@ func (z nat) montgomery(x, y, m nat, k Word, n int) nat {
if len(x) != n || len(y) != n || len(m) != n {
panic("math/big: mismatched montgomery number lengths")
}
z = z.make(n)
z = z.make(n * 2)
z.clear()
var c Word
for i := 0; i < n; i++ {
d := y[i]
c2 := addMulVVW(z, x, d)
t := z[0] * k
c3 := addMulVVW(z, m, t)
copy(z, z[1:])
c2 := addMulVVW(z[i:n+i], x, d)
t := z[i] * k
c3 := addMulVVW(z[i:n+i], m, t)
cx := c + c2
cy := cx + c3
z[n-1] = cy
z[n+i] = cy
if cx < c2 || cy < c3 {
c = 1
} else {
@ -232,9 +231,11 @@ func (z nat) montgomery(x, y, m nat, k Word, n int) nat {
}
}
if c != 0 {
subVV(z, z, m)
subVV(z[:n], z[n:], m)
} else {
copy(z[:n], z[n:])
}
return z
return z[:n]
}
// Fast version of z[0:n+n>>1].add(z[0:n+n>>1], x[0:n]) w/o bounds checks.