Parallel pippenger from blst (#211)

grandinetech · Apr 6, 2023 · c4d4893 · c4d4893
2 parents 2079928 + 7e3941f
commit c4d4893
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Showing 2 changed files with 42 additions and 15 deletions.
diff --git a/blst-from-scratch/src/kzg_proofs.rs b/blst-from-scratch/src/kzg_proofs.rs
@@ -1,51 +1,76 @@
 extern crate alloc;
 
+#[cfg(not(feature = "parallel"))]
 use alloc::vec;
 use alloc::vec::Vec;
+#[cfg(not(feature = "parallel"))]
 use core::ptr;
 
+#[cfg(feature = "parallel")]
+use blst::p1_affines;
+#[cfg(not(feature = "parallel"))]
 use blst::{
-    blst_fp12_is_one, blst_p1, blst_p1_affine, blst_p1_cneg, blst_p1_to_affine,
     blst_p1s_mult_pippenger, blst_p1s_mult_pippenger_scratch_sizeof, blst_p1s_to_affine,
-    blst_p2_affine, blst_p2_to_affine, blst_scalar, limb_t, Pairing,
+    blst_scalar, limb_t,
 };
+
+use blst::{
+    blst_fp12_is_one, blst_p1, blst_p1_affine, blst_p1_cneg, blst_p1_to_affine, blst_p2_affine,
+    blst_p2_to_affine, Pairing,
+};
+
 use kzg::{G1Mul, G1};
 
-use crate::consts::G1_IDENTITY;
 use crate::types::fr::FsFr;
 use crate::types::g1::FsG1;
 use crate::types::g2::FsG2;
 
-pub fn g1_linear_combination(out: &mut FsG1, p: &[FsG1], coeffs: &[FsFr], len: usize) {
+pub fn g1_linear_combination(out: &mut FsG1, points: &[FsG1], scalars: &[FsFr], len: usize) {
     if len < 8 {
-        // Direct approach
-        let mut tmp;
-        *out = G1_IDENTITY;
+        *out = FsG1::default();
         for i in 0..len {
-            tmp = p[i].mul(&coeffs[i]);
+            let tmp = points[i].mul(&scalars[i]);
             *out = out.add_or_dbl(&tmp);
         }
-    } else {
+        return;
+    }
+
+    #[cfg(feature = "parallel")]
+    {
+        let points = unsafe { core::slice::from_raw_parts(points.as_ptr() as *const blst_p1, len) };
+        let points = p1_affines::from(points);
+
+        let mut scalar_bytes: Vec<u8> = Vec::with_capacity(len * 32);
+        for bytes in scalars.iter().map(|b| b.to_scalar()) {
+            scalar_bytes.extend_from_slice(&bytes);
+        }
+
+        let res = points.mult(scalar_bytes.as_slice(), 255);
+        *out = FsG1(res)
+    }
+
+    #[cfg(not(feature = "parallel"))]
+    {
         let mut scratch: Vec<u8>;
         unsafe {
             scratch = vec![0u8; blst_p1s_mult_pippenger_scratch_sizeof(len) as usize];
         }
 
         let mut p_affine = vec![blst_p1_affine::default(); len];
-        let mut scalars = vec![blst_scalar::default(); len];
+        let mut p_scalars = vec![blst_scalar::default(); len];
 
-        let p_arg: [*const blst_p1; 2] = [&p[0].0, ptr::null()];
+        let p_arg: [*const blst_p1; 2] = [&points[0].0, ptr::null()];
         unsafe {
             blst_p1s_to_affine(p_affine.as_mut_ptr(), p_arg.as_ptr(), len);
         }
 
         for i in 0..len {
-            scalars[i] = blst_scalar {
-                b: coeffs[i].to_scalar(),
+            p_scalars[i] = blst_scalar {
+                b: scalars[i].to_scalar(),
             };
         }
 
-        let scalars_arg: [*const blst_scalar; 2] = [scalars.as_ptr(), ptr::null()];
+        let scalars_arg: [*const blst_scalar; 2] = [p_scalars.as_ptr(), ptr::null()];
         let points_arg: [*const blst_p1_affine; 2] = [p_affine.as_ptr(), ptr::null()];
         unsafe {
             blst_p1s_mult_pippenger(

diff --git a/blst-from-scratch/src/types/g2.rs b/blst-from-scratch/src/types/g2.rs
@@ -2,7 +2,9 @@ use blst::{
     blst_fp2, blst_p2, blst_p2_add_or_double, blst_p2_cneg, blst_p2_double, blst_p2_is_equal,
     blst_p2_mult, blst_scalar, blst_scalar_from_fr,
 };
-use kzg::{Fr, G2Mul, G2};
+#[cfg(feature = "std")]
+use kzg::Fr;
+use kzg::{G2Mul, G2};
 
 use crate::consts::{G2_GENERATOR, G2_NEGATIVE_GENERATOR};
 use crate::types::fr::FsFr;