add: compute matrix (#6550)

* add: compute matrix

* rm unsused imports

* rm unused imports 2

* rm bin

* rm unused line

* improve doc

* rid space on proc sig

* review 1

* added seeded PRNG

* randomize blob count as well, with smaller seed

* review 2

AllTests-mainnet.md

@@ -536,6 +536,11 @@ OK: 5/5 Fail: 0/5 Skip: 0/5
 + EIP7594: Extended Sample Count                                                             OK
 ```
 OK: 1/1 Fail: 0/1 Skip: 0/1
+## EIP-7594 Unit Tests
+```diff
++ EIP-7594: Compute Matrix                                                                   OK
+```
+OK: 1/1 Fail: 0/1 Skip: 0/1
 ## EL Configuration
 ```diff
 + Empty config file                                                                          OK
@@ -1119,4 +1124,4 @@ OK: 2/2 Fail: 0/2 Skip: 0/2
 OK: 9/9 Fail: 0/9 Skip: 0/9
 
 ---TOTAL---
-OK: 760/765 Fail: 0/765 Skip: 5/765
+OK: 761/766 Fail: 0/766 Skip: 5/766

beacon_chain/spec/eip7594_helpers.nim

@@ -99,6 +99,27 @@ func get_custody_column_list*(node_id: NodeId,
 
   sortedColumnIndexList(ColumnIndex(columns_per_subnet), subnet_ids)
 
+# https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.5/specs/_features/eip7594/das-core.md#compute_matrix
+proc compute_matrix*(blobs: seq[KzgBlob]): Result[seq[MatrixEntry], cstring] =
+  ## `compute_matrix` helper demonstrates the relationship
+  ## between blobs and the `MatrixEntries`
+  var extended_matrix: seq[MatrixEntry]
+
+  for blbIdx, blob in blobs.pairs:
+    let cellsAndProofs = computeCellsAndKzgProofs(blob)
+    if not cellsAndProofs.isOk:
+      return err("Computing Extended Matrix: Issue computing cells and proofs")
+
+    for i in 0..<eip7594.CELLS_PER_EXT_BLOB:
+      extended_matrix.add(MatrixEntry(
+        cell: cellsAndProofs.get.cells[i],
+        kzg_proof: cellsAndProofs.get.proofs[i],
+        row_index: blbIdx.uint64,
+        column_index: i.uint64
+      ))
+
+  ok(extended_matrix)
+
 # https://github.com/ethereum/consensus-specs/blob/v1.5.0-alpha.5/specs/_features/eip7594/peer-sampling.md#get_extended_sample_count
 func get_extended_sample_count*(samples_per_slot: int,
                                 allowed_failures: int):

tests/test_eip7594_helpers.nim

@@ -9,8 +9,62 @@
 {.used.}
 
 import
+  std/random,
   unittest2,
-  ../beacon_chain/spec/[helpers, eip7594_helpers]
+  results,
+  kzg4844/[kzg_abi, kzg],
+  ./consensus_spec/[os_ops, fixtures_utils],
+  ../beacon_chain/spec/[helpers, eip7594_helpers],
+  ../beacon_chain/spec/datatypes/[eip7594, deneb]
+
+from std/strutils import rsplit
+
+block:
+  template sourceDir: string = currentSourcePath.rsplit(DirSep, 1)[0]
+  doAssert loadTrustedSetup(
+    sourceDir &
+      "/../vendor/nim-kzg4844/kzg4844/csources/src/trusted_setup.txt", 0).isOk
+
+# 114 is the MSB (most/max significant byte)
+# such that BLS modulus does not overflow
+const MAX_TOP_BYTE = 114
+
+proc createSampleKzgBlobs(n: int, seed: int): seq[KzgBlob] =
+  var
+    blobs: seq[KzgBlob] = @[]
+    # Initialize the PRNG with the given seed
+    rng = initRand(seed)
+  for blobIndex in 0..<n:
+    var blob: array[int(BYTES_PER_BLOB), byte]
+    # Fill the blob with random bytes using the seeded PRNG
+    for byteIndex in 0..<int(BYTES_PER_BLOB):
+      blob[byteIndex] = rng.rand(byte)
+    # Adjust bytes according to the given condition
+    for byteIndex in 0..<int(BYTES_PER_BLOB):
+      if blob[byteIndex] > MAX_TOP_BYTE and
+         byteIndex mod kzg_abi.BYTES_PER_FIELD_ELEMENT == 0:
+        blob[byteIndex] = MAX_TOP_BYTE
+    blobs.add(KzgBlob(bytes: blob))
+  blobs
+
+iterator chunks[T](lst: seq[T], n: int): seq[T] =
+  ## Iterator that yields N-sized chunks from the list.
+  for i in countup(0, len(lst) - 1, n):
+    yield lst[i..min(i + n - 1, len(lst) - 1)]
+
+suite "EIP-7594 Unit Tests":
+  test "EIP-7594: Compute Matrix":
+    proc testComputeExtendedMatrix() =
+      var
+        rng = initRand(126)
+        blob_count = rng.rand(1..(deneb.MAX_BLOB_COMMITMENTS_PER_BLOCK.int))
+      let
+        input_blobs = createSampleKzgBlobs(blob_count, rng.rand(int))
+        extended_matrix = compute_matrix(input_blobs)
+      doAssert extended_matrix.get.len == kzg_abi.CELLS_PER_EXT_BLOB * blob_count
+      for row in chunks(extended_matrix.get, kzg_abi.CELLS_PER_EXT_BLOB):
+        doAssert len(row) == kzg_abi.CELLS_PER_EXT_BLOB
+    testComputeExtendedMatrix()
 
 suite "EIP-7594 Sampling Tests":
   test "EIP7594: Extended Sample Count":
@@ -44,3 +98,5 @@ suite "EIP-7594 Sampling Tests":
         check: get_extended_sample_count(
             samplesPerSlot, allowed_failures) == extendedSampleCount
     testExtendedSampleCount()
+
+doAssert freeTrustedSetup().isOk