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Shuffling for 32 bit platforms #7725

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Shuffling for 32 bit platforms #7725

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fb5450e
Fix shuffle_list to work on 32 bit platforms
ec2 Jul 9, 2025
e419687
ruint doesnt allow operations on u64 on 32 bit platforms
ec2 Jul 9, 2025
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3 changes: 1 addition & 2 deletions consensus/swap_or_not_shuffle/src/shuffle_list.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -96,8 +96,7 @@ pub fn shuffle_list(
loop {
buf.set_round(r);

let pivot = buf.raw_pivot() as usize % list_size;

let pivot = (buf.raw_pivot() % list_size as u64) as usize;
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This looks good to me. It should allow us to support lists up to size 2**32 (4B) on 32-bit platforms.

let mirror = (pivot + 1) >> 1;

buf.mix_in_position(pivot >> 8);
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2 changes: 1 addition & 1 deletion consensus/types/src/subnet_id.rs
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Expand Up @@ -105,7 +105,7 @@ impl SubnetId {

let node_id = U256::from_be_slice(&raw_node_id);
// calculate the prefixes used to compute the subnet and shuffling
let node_id_prefix = (node_id >> (NODE_ID_BITS - prefix_bits))
let node_id_prefix = (node_id >> (NODE_ID_BITS - prefix_bits) as u32)
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Rather than casting between u64 I think we may as well just write everything in terms of u32s

diff --git a/consensus/types/src/subnet_id.rs b/consensus/types/src/subnet_id.rs
index 061b295276..5f93161f22 100644
--- a/consensus/types/src/subnet_id.rs
+++ b/consensus/types/src/subnet_id.rs
@@ -11,7 +11,7 @@ const MAX_SUBNET_ID: usize = 64;
 
 /// The number of bits in a Discovery `NodeId`. This is used for binary operations on the node-id
 /// data.
-const NODE_ID_BITS: u64 = 256;
+const NODE_ID_BITS: u32 = 256;
 
 static SUBNET_ID_TO_STRING: LazyLock<Vec<String>> = LazyLock::new(|| {
     let mut v = Vec::with_capacity(MAX_SUBNET_ID);
@@ -101,11 +101,11 @@ impl SubnetId {
         spec: &ChainSpec,
     ) -> impl Iterator<Item = SubnetId> {
         // The bits of the node-id we are using to define the subnets.
-        let prefix_bits = spec.attestation_subnet_prefix_bits as u64;
+        let prefix_bits = spec.attestation_subnet_prefix_bits as u32;
 
         let node_id = U256::from_be_slice(&raw_node_id);
         // calculate the prefixes used to compute the subnet and shuffling
-        let node_id_prefix = (node_id >> (NODE_ID_BITS - prefix_bits) as u32)
+        let node_id_prefix = (node_id >> (NODE_ID_BITS - prefix_bits))
             .as_le_slice()
             .get_u64_le();

.as_le_slice()
.get_u64_le();

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