rct: avoid repeated unnecessary conversions when accummulating

src/ringct/rctOps.cpp

@@ -252,6 +252,25 @@ namespace rct {
       return k;
     }
 
+    rct::key addKeys(const keyV &A) {
+      if (A.empty())
+        return rct::identity();
+      ge_p3 p3, tmp;
+      CHECK_AND_ASSERT_THROW_MES_L1(ge_frombytes_vartime(&p3, A[0].bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
+      for (size_t i = 1; i < A.size(); ++i)
+      {
+        CHECK_AND_ASSERT_THROW_MES_L1(ge_frombytes_vartime(&tmp, A[i].bytes) == 0, "ge_frombytes_vartime failed at "+boost::lexical_cast<std::string>(__LINE__));
+        ge_cached p2;
+        ge_p3_to_cached(&p2, &tmp);
+        ge_p1p1 p1;
+        ge_add(&p1, &p3, &p2);
+        ge_p1p1_to_p3(&p3, &p1);
+      }
+      rct::key res;
+      ge_p3_tobytes(res.bytes, &p3);
+      return res;
+    }
+
     //addKeys1
     //aGB = aG + B where a is a scalar, G is the basepoint, and B is a point
     void addKeys1(key &aGB, const key &a, const key & B) {

src/ringct/rctOps.h

@@ -132,6 +132,7 @@ namespace rct {
     //for curve points: AB = A + B
     void addKeys(key &AB, const key &A, const key &B);
     rct::key addKeys(const key &A, const key &B);
+    rct::key addKeys(const keyV &A);
     //aGB = aG + B where a is a scalar, G is the basepoint, and B is a point
     void addKeys1(key &aGB, const key &a, const key & B);
     //aGbB = aG + bB where a, b are scalars, G is the basepoint and B is a point

src/ringct/rctSigs.cpp

@@ -963,18 +963,16 @@ namespace rct {
           const bool bulletproof = is_rct_bulletproof(rv.type);
           const keyV &pseudoOuts = bulletproof ? rv.p.pseudoOuts : rv.pseudoOuts;
 
-          key sumOutpks = identity();
+          rct::keyV masks(rv.outPk.size());
           for (size_t i = 0; i < rv.outPk.size(); i++) {
-            addKeys(sumOutpks, sumOutpks, rv.outPk[i].mask);
+            masks[i] = rv.outPk[i].mask;
           }
+          key sumOutpks = addKeys(masks);
           DP(sumOutpks);
-          key txnFeeKey = scalarmultH(d2h(rv.txnFee));
+          const key txnFeeKey = scalarmultH(d2h(rv.txnFee));
           addKeys(sumOutpks, txnFeeKey, sumOutpks);
 
-          key sumPseudoOuts = identity();
-          for (size_t i = 0 ; i < pseudoOuts.size() ; i++) {
-            addKeys(sumPseudoOuts, sumPseudoOuts, pseudoOuts[i]);
-          }
+          key sumPseudoOuts = addKeys(pseudoOuts);
           DP(sumPseudoOuts);
 
           //check pseudoOuts vs Outs..