rct: add a zeroCommit cache for common pre-rct case

This is called for every pre-rct output at blockchain sync time,
and a lot of them wil hit the cache, saving a scalarmult each.

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/unit_tests/ringct.cpp b/tests/unit_tests/ringct.cpp
index 3877ef785..52bdb00cf 100644
--- a/tests/unit_tests/ringct.cpp
+++ b/tests/unit_tests/ringct.cpp
@@ -1086,6 +1086,25 @@ TEST(ringct, zeroCommmit)
   ASSERT_EQ(z, manual);
 }
 
+static rct::key uncachedZeroCommit(uint64_t amount)
+{
+  const rct::key am = rct::d2h(amount);
+  const rct::key bH = rct::scalarmultH(am);
+  return rct::addKeys(rct::G, bH);
+}
+
+TEST(ringct, zeroCommitCache)
+{
+  ASSERT_EQ(rct::zeroCommit(0), uncachedZeroCommit(0));
+  ASSERT_EQ(rct::zeroCommit(1), uncachedZeroCommit(1));
+  ASSERT_EQ(rct::zeroCommit(2), uncachedZeroCommit(2));
+  ASSERT_EQ(rct::zeroCommit(10), uncachedZeroCommit(10));
+  ASSERT_EQ(rct::zeroCommit(200), uncachedZeroCommit(200));
+  ASSERT_EQ(rct::zeroCommit(1000000000), uncachedZeroCommit(1000000000));
+  ASSERT_EQ(rct::zeroCommit(3000000000000), uncachedZeroCommit(3000000000000));
+  ASSERT_EQ(rct::zeroCommit(900000000000000), uncachedZeroCommit(900000000000000));
+}
+
 TEST(ringct, H)
 {
   ge_p3 p3;