codex-storage
/
constantine
mirror of https://github.com/codex-storage/constantine.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Fix 50% perf regression (2x with GCC) on binary GCD based inversion (#135) 

* Fix 50% perf regresion Revert part of #95, fix #134

* Deactivate inversion via addition chain for BW6-761. 2x slower than Euclid
This commit is contained in:
Mamy Ratsimbazafy 2021-01-23 21:44:22 +01:00 committed by GitHub
parent 82819b1b10
commit 5b1d280486
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 30 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
constantine/arithmetic/limbs.nim
View File

@ -246,16 +246,22 @@ func cadd*(a: var Limbs, b: Limbs, ctl: SecretBool): Carry =
## The carry is always computed whether ctl is true or false
##
## Time and memory accesses are the same whether a copy occurs or not
var t = a
result = t.add(b)
a.ccopy(t, ctl)
result = Carry(0)
var sum: SecretWord
for i in 0 ..< a.len:
addC(result, sum, a[i], b[i], result)
ctl.ccopy(a[i], sum)
func cadd*(a: var Limbs, w: SecretWord, ctl: SecretBool): Carry =
func cadd*(a: var Limbs, w: SecretWord, ctl: SecretBool): Borrow =
## Limbs conditional addition, sub a number that fits in a word
## Returns the borrow
var t = a
result = t.add(w)
a.ccopy(t, ctl)
result = Carry(0)
var diff: SecretWord
addC(result, diff, a[0], w, result)
ctl.ccopy(a[0], diff)
for i in 1 ..< a.len:
addC(result, diff, a[i], Zero, result)
ctl.ccopy(a[i], diff)
func csub*(a: var Limbs, b: Limbs, ctl: SecretBool): Borrow =
## Limbs conditional substraction
@ -266,16 +272,22 @@ func csub*(a: var Limbs, b: Limbs, ctl: SecretBool): Borrow =
## The borrow is always computed whether ctl is true or false
##
## Time and memory accesses are the same whether a copy occurs or not
var t = a
result = t.sub(b)
a.ccopy(t, ctl)
result = Borrow(0)
var diff: SecretWord
for i in 0 ..< a.len:
subB(result, diff, a[i], b[i], result)
ctl.ccopy(a[i], diff)
func csub*(a: var Limbs, w: SecretWord, ctl: SecretBool): Borrow =
## Limbs conditional substraction, sub a number that fits in a word
## Returns the borrow
var t = a
result = t.sub(w)
a.ccopy(t, ctl)
result = Borrow(0)
var diff: SecretWord
subB(result, diff, a[0], w, result)
ctl.ccopy(a[0], diff)
for i in 1 ..< a.len:
subB(result, diff, a[i], Zero, result)
ctl.ccopy(a[i], diff)
func cneg*(a: var Limbs, ctl: CTBool) =
## Conditional negation.

7
constantine/curves/zoo_inversions.nim
View File

@ -26,8 +26,11 @@ export
func hasInversionAddchain*(C: static Curve): static bool =
# TODO: For now we don't activate the addition chains
# for Secp256k1
# Performance is slower than GCD
when C in {BN254_Nogami, BN254_Snarks, BLS12_377, BLS12_381, BW6_761}:
# Performance is slower than GCD (to investigate)
# For BW6-761 the addition chain is over 2x slower than Euclid-based inversion
# due to multiplication being so costly with 12 limbs (grows quadratically)
# while Euclid costs grows linearly.
when C in {BN254_Nogami, BN254_Snarks, BLS12_377, BLS12_381}:
true
else:
false