From f17c0389b9c65369a98e91b319f20627131da0bd Mon Sep 17 00:00:00 2001
From: Balazs Komuves <bkomuves@gmail.com>
Date: Sat, 13 Jun 2026 14:20:17 +0200
Subject: [PATCH] add some quick&dirty FFT benchmarks

---
 bench/.gitignore          |   2 +
 bench/bench_fft.nim       | 104 ++++++++++++++++++++++++++++++++++++++
 bench/bench_fft.nimble    |  13 +++++
 bench/nim.cfg             |   1 +
 bench/shared.nim          |  23 +++++++++
 groth16.nimble            |   2 +-
 groth16/bn128/arrays.nim  |  61 ++++++++++++++++++++++
 tests/groth16/testFFT.nim |  54 +++-----------------
 8 files changed, 213 insertions(+), 47 deletions(-)
 create mode 100644 bench/.gitignore
 create mode 100644 bench/bench_fft.nim
 create mode 100644 bench/bench_fft.nimble
 create mode 100644 bench/nim.cfg
 create mode 100644 bench/shared.nim
 create mode 100644 groth16/bn128/arrays.nim

diff --git a/bench/.gitignore b/bench/.gitignore
new file mode 100644
index 0000000..b302f53
--- /dev/null
+++ b/bench/.gitignore
@@ -0,0 +1,2 @@
+.DS_Store
+bench_fft
diff --git a/bench/bench_fft.nim b/bench/bench_fft.nim
new file mode 100644
index 0000000..e3d2d6c
--- /dev/null
+++ b/bench/bench_fft.nim
@@ -0,0 +1,104 @@
+
+#
+# nimble build -d:release
+#
+
+import strformat
+
+import taskpools
+
+import constantine/math/arithmetic
+import constantine/named/properties_fields
+
+import groth16/bn128
+import groth16/bn128/msm
+import groth16/bn128/arrays
+
+import groth16/math/domain
+import groth16/math/ntt
+import groth16/dynamic/group_fft
+
+import shared
+
+#-------------------------------------------------------------------------------
+
+when isMainModule:
+
+  echo "quick & dirty FFT benchmarks"
+  
+  let nthreads: int = 8
+  let N:        int = 8192
+
+  let D = createDomain(N)
+  let xs : seq[Fr[BN254_Snarks]] = randFrSeq(N)
+  let gs : seq[AffG1]            = randG1Seq(N)
+
+  var ys, zs: seq[Fr[BN254_Snarks]]
+  var hs, rs: seq[AffG1]
+
+  var pool = Taskpool.new(nthreads)
+
+  #-----------------------------------------------------------------------------
+
+  echo "\n----------------------------------------"
+  echo "*** scalar multiplications\n"
+
+  hs = newSeq[AffG1](N)
+  withMeasureTime(true , fmt"{N} individual scalar multiplications      "):
+    for i in 0..<N: 
+      hs[i] = xs[i] ** gs[i]
+
+  var sum_naive: AffG1
+  withMeasureTime(true , fmt"naive simulated MSM of size {N}            "):
+    for i in 0..<N: 
+      hs[i] = xs[i] ** gs[i]
+      if i==0:
+        sum_naive = hs[i]
+      else:
+        sum_naive += hs[i]
+
+  var sum_msm: AffG1
+  withMeasureTime(true , fmt"proper MSM of size {N}                     "):
+    sum_msm = msmConstantineG1( xs, gs )
+
+  var sum_multi: AffG1
+  withMeasureTime(true , fmt"multithreaded MSM of size {N} ({nthreads} threads)  "):
+    let sum_multi = msmMultiThreadedG1( xs , gs , pool )
+
+  echo "naive == msm : " & $(sum_naive === sum_msm)
+
+  #-----------------------------------------------------------------------------
+
+  echo "\n----------------------------------------"
+  echo "*** field FFTs\n"
+
+  withMeasureTime(true , fmt"field NTT of size {N}           "): 
+    ys = forwardNTT(xs, D)
+
+  withMeasureTime(true , fmt"unscaled field INTT of size {N} "): 
+    zs = unscaledInverseNTT(ys, D) 
+
+  withMeasureTime(true , fmt"field INTT of size {N}          "): 
+    zs = inverseNTT(ys, D) 
+
+  echo "xs == zs : " & $isEqualFrSeq(xs , zs)
+ 
+  #-----------------------------------------------------------------------------
+
+  echo "\n----------------------------------------"
+  echo "*** group FFTs\n"
+
+  withMeasureTime(true , fmt"group FFT of size {N}           "): 
+    hs = forwardGroupFFT(gs, D)
+
+  withMeasureTime(true , fmt"unscaled group IFFT of size {N} "): 
+    rs = unscaledInverseGroupFFT(hs, D) 
+
+  withMeasureTime(true , fmt"group IFFT of size {N}          "): 
+    rs = inverseGroupFFT(hs, D) 
+
+  echo "gs == rs : " & $isEqualG1Seq(gs , rs)
+
+  echo "\n"
+
+#-------------------------------------------------------------------------------
diff --git a/bench/bench_fft.nimble b/bench/bench_fft.nimble
new file mode 100644
index 0000000..3a38441
--- /dev/null
+++ b/bench/bench_fft.nimble
@@ -0,0 +1,13 @@
+
+version     = "0.0.1"
+author      = "Balazs Komuves"
+description = "FFT benchmarks"
+license     = "MIT OR Apache-2.0"
+
+binDir      = "build"
+bin         = @["bench_fft"]
+
+requires "nim >= 2.2.0"
+requires "https://github.com/status-im/nim-taskpools >= 0.0.5"
+requires "https://github.com/mratsim/constantine"
+requires "groth16 >= 0.1.2"
diff --git a/bench/nim.cfg b/bench/nim.cfg
new file mode 100644
index 0000000..0f840a1
--- /dev/null
+++ b/bench/nim.cfg
@@ -0,0 +1 @@
+--path:".."
diff --git a/bench/shared.nim b/bench/shared.nim
new file mode 100644
index 0000000..ef568d1
--- /dev/null
+++ b/bench/shared.nim
@@ -0,0 +1,23 @@
+
+import strformat
+import times, strutils
+
+#-------------------------------------------------------------------------------
+
+func seconds*(x: float): string = fmt"{x:.4f} seconds"
+
+func quoted*(s: string): string = fmt"`{s:s}`"
+
+template withMeasureTime*(doPrint: bool, text: string, code: untyped) =
+  block:
+    if doPrint:
+      let t0 = epochTime()
+      code
+      let elapsed = epochTime() - t0
+      let elapsedStr = elapsed.formatFloat(format = ffDecimal, precision = 4)
+      echo ( text & " took " & elapsedStr & " seconds" )
+    else:
+      code
+
+#-------------------------------------------------------------------------------
+
diff --git a/groth16.nimble b/groth16.nimble
index ec8762a..be06ac4 100644
--- a/groth16.nimble
+++ b/groth16.nimble
@@ -4,7 +4,7 @@ author      = "Balazs Komuves"
 description = "Groth16 proof system"
 license     = "MIT OR Apache-2.0"
 
-skipDirs    = @["groth16/example"]
+skipDirs    = @["groth16/example","bench"]
 binDir      = "build"
 namedBin    = {"cli/cli_main": "nim-groth16"}.toTable()
 installExt  = @["nim"]
diff --git a/groth16/bn128/arrays.nim b/groth16/bn128/arrays.nim
new file mode 100644
index 0000000..0b65368
--- /dev/null
+++ b/groth16/bn128/arrays.nim
@@ -0,0 +1,61 @@
+
+import constantine/math/arithmetic
+import constantine/named/properties_fields
+
+import groth16/bn128/fields
+import groth16/bn128/curves
+import groth16/bn128/rnd
+
+#-------------------------------------------------------------------------------
+# Fr arrays
+
+proc randFrSeq*(N: int) : seq[Fr[BN254_Snarks]] = 
+  var xs : seq[Fr[BN254_Snarks]] = newSeq[Fr[BN254_Snarks]]( N )
+  for i in 0..<N:
+    xs[i] = randFr()
+  return xs
+
+func isEqualFrSeq*(xs: seq[Fr[BN254_Snarks]], ys: seq[Fr[BN254_Snarks]]): bool =
+  let N = xs.len
+  let M = ys.len
+
+  if N != M:
+    return false
+  else:
+    var ok: bool = true
+    for i in 0..<N:
+      ok = ok and (xs[i] === ys[i])
+    return ok
+
+proc scaleFrSeqInPlace*(s: Fr[BN254_Snarks], arr: var seq[Fr[BN254_Snarks]] ) = 
+  let N = arr.len  
+  for i in 0..<N:
+    arr[i] *= s
+
+#-------------------------------------------------------------------------------
+# G1 arrays
+
+proc randG1Seq*(N: int) : seq[G1] = 
+  var xs : seq[G1] = newSeq[G1]( N )
+  for i in 0..<N:
+    xs[i] = randG1()
+  return xs
+
+func isEqualG1Seq*(xs: seq[G1], ys: seq[G1] ): bool =
+  let N = xs.len
+  let M = ys.len
+
+  if N != M:
+    return false
+  else:
+    var ok: bool = true
+    for i in 0..<N:
+      ok = ok and (xs[i] === ys[i])
+    return ok
+
+proc scaleG1SeqInPlace*(s: Fr[BN254_Snarks], arr: var seq[G1] ) = 
+  let N = arr.len  
+  for i in 0..<N:
+    arr[i] = s ** arr[i]
+
+#-------------------------------------------------------------------------------
diff --git a/tests/groth16/testFFT.nim b/tests/groth16/testFFT.nim
index 6971459..56c23d6 100644
--- a/tests/groth16/testFFT.nim
+++ b/tests/groth16/testFFT.nim
@@ -11,6 +11,7 @@ import groth16/bn128/fields
 import groth16/bn128/curves
 import groth16/bn128/rnd
 import groth16/bn128/debug
+import groth16/bn128/arrays
 
 import groth16/math/domain
 import groth16/math/ntt
@@ -19,51 +20,6 @@ import groth16/dynamic/group_fft
 
 #-------------------------------------------------------------------------------
 
-proc randFrSeq(N: int) : seq[Fr[BN254_Snarks]] = 
-  var xs : seq[Fr[BN254_Snarks]] = newSeq[Fr[BN254_Snarks]]( N )
-  for i in 0..<N:
-    xs[i] = randFr()
-  return xs
-
-proc scaleFrSeqInPlace(s: Fr[BN254_Snarks], arr: var seq[Fr[BN254_Snarks]] ) = 
-  let N = arr.len  
-  for i in 0..<N:
-    arr[i] *= s
-
-func isEqualFrSeq(xs: seq[Fr[BN254_Snarks]], ys: seq[Fr[BN254_Snarks]]): bool =
-  let N = xs.len
-  let M = ys.len
-
-  if N != M:
-    return false
-  else:
-    var ok: bool = true
-    for i in 0..<N:
-      ok = ok and (xs[i] === ys[i])
-    return ok
-
-#---------------------------------------
-
-proc randG1Seq(N: int) : seq[G1] = 
-  var xs : seq[G1] = newSeq[G1]( N )
-  for i in 0..<N:
-    xs[i] = randG1()
-  return xs
-
-func isEqualG1Seq(xs: seq[G1], ys: seq[G1] ): bool =
-  let N = xs.len
-  let M = ys.len
-
-  if N != M:
-    return false
-  else:
-    var ok: bool = true
-    for i in 0..<N:
-      ok = ok and (xs[i] === ys[i])
-    return ok
-
-#-------------------------------------------------------------------------------
-
 suite "field NTT checks":
 
   let D = createDomain(128)
@@ -100,11 +56,17 @@ suite "group FFT checks (for the group G1)":
     let rs = inverseGroupFFT(hs, D) 
     check isEqualG1Seq( gs , rs )
   
-  test "NTT(INTT(xs) == xs":
+  test "FFT(IFFT(xs) == xs":
     let hs = inverseGroupFFT(gs, D)
     let rs = forwardGroupFFT(hs, D) 
     check isEqualG1Seq( gs , rs )
 
+  test "FFT(unscaledIFFT(gs) == N * gs":
+    let hs = unscaledInverseGroupFFT(gs, D)
+    let rs = forwardGroupFFT(hs, D) 
+    var qs = gs
+    scaleG1SeqInPlace(intToFr(N) , qs)
+    check isEqualG1Seq( qs , rs )
 
 #-------------------------------------------------------------------------------