revert Fix half up in round

Author: JkSelf

velox/expression/tests/ExprTest.cpp

@@ -839,6 +839,14 @@ TEST_F(ExprTest, shortCircuit) {
   assertEqualVectors(expectedResult, result);
 }
 
+TEST_F(ExprTest, round) {
+  vector_size_t size = 4;
+  auto a = makeConstant(-1.0249999999999999, size);
+  auto result = evaluate("round(c0, cast (3 as int))", makeRowVector({a}));
+  auto expectedResult = makeConstant(-1.025, size);
+  assertEqualVectors(expectedResult, result);
+}
+
 // Test common sub-expression (CSE) optimization with encodings.
 // CSE evaluation may happen in different contexts, e.g. original input rows
 // on first evaluation and base vectors uncovered through peeling of encodings

velox/functions/prestosql/ArithmeticImpl.h

@@ -44,15 +44,10 @@ round(const TNum& number, const TDecimals& decimals = 0) {
   }
 
   double factor = std::pow(10, decimals);
-  double variance = 0.1;
   if (number < 0) {
-    return (std::round(
-                std::nextafter(number, number - variance) * factor * -1) /
-            factor) *
-        -1;
+    return (std::round(number * factor * -1) / factor) * -1;
   }
-  return std::round(std::nextafter(number, number + variance) * factor) /
-      factor;
+  return std::round(number * factor) / factor;
 }
 
 // This is used by Velox for floating points plus.