[Java] Choose The Correct RoundingMode For Checking Decimal OutOfBounds

java/src/main/java/ai/rapids/cudf/DecimalUtils.java

@@ -82,13 +82,15 @@ public static ColumnVector lessThan(ColumnView lhs, BigDecimal rhs) {
     int leftScale = lhs.getType().getScale();
     int leftPrecision = lhs.getType().getDecimalMaxPrecision();
 
-    // First we have to round the scalar (rhs) to the same scale as lhs.  Because this is a
-    // less than and it is rhs that we are rounding, we will round away from 0 (UP)
-    // to make sure we always return the correct value.
+    // First we have to round the scalar (rhs) to the same scale as lhs.
+    // Because this is a less-than, and it is rhs that we are rounding, we will round away from 0 (UP) in case rhs is
+    // positive and toward 0 (DOWN) if rhs is negative to make sure we always return the correct value.
     // For example:
-    //      100.1 < 100.19
-    // If we rounded down the rhs 100.19 would become 100.1, and now 100.1 is not < 100.1
-    BigDecimal roundedRhs = rhs.setScale(-leftScale, BigDecimal.ROUND_UP);
+    //      ex:1 100.1 < 100.19
+    //      ex:2 -100.2 < -100.19
+    // In ex:1 If we rounded down the rhs 100.19 would become 100.1, and now 100.1 is not < 100.1
+    // In ex:2 If we rounded up the rhs -100.19 would become -100.2, and now -100.2 is not < -100.2
+    BigDecimal roundedRhs = rhs.setScale(-leftScale, rhs.signum() > 0 ? BigDecimal.ROUND_UP : BigDecimal.ROUND_DOWN);
 
     if (roundedRhs.precision() > leftPrecision) {
       // converting rhs to the same precision as lhs would result in an overflow/error, but
@@ -142,7 +144,16 @@ public static ColumnVector greaterThan(ColumnView lhs, BigDecimal rhs) {
     // For example:
     //      100.2 > 100.19
     // If we rounded up the rhs 100.19 would become 100.2, and now 100.2 is not > 100.2
-    BigDecimal roundedRhs = rhs.setScale(-cvScale, BigDecimal.ROUND_DOWN);
+
+    // First we have to round the scalar (rhs) to the same scale as lhs.
+    // Because this is a greater-than, and it is rhs that we are rounding, we will round towards 0 (DOWN) in case rhs is
+    // positive and away from 0 (UP) if rhs is negative to make sure we always return the correct value.
+    // For example:
+    //      ex:1 100.2 > 100.19
+    //      ex:2 -100.1 > -100.19
+    // In ex:1 If we rounded up the rhs 100.19 would become 100.2, and now 100.2 is not > 100.2
+    // In ex:2 If we rounded down the rhs -100.19 would become -100.1, and now -100.1 is not > -100.1
+    BigDecimal roundedRhs = rhs.setScale(-cvScale, rhs.signum() > 0 ? BigDecimal.ROUND_DOWN : BigDecimal.ROUND_UP);
 
     if (roundedRhs.precision() > maxPrecision) {
       // converting rhs to the same precision as lhs would result in an overflow/error, but

java/src/test/java/ai/rapids/cudf/DecimalUtilsTest.java

@@ -0,0 +1,40 @@
+/*
+ *
+ *  Copyright (c) 2024, NVIDIA CORPORATION.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+
+package ai.rapids.cudf;
+
+import org.junit.jupiter.api.Test;
+
+import java.math.BigDecimal;
+import static ai.rapids.cudf.AssertUtils.assertColumnsAreEqual;
+
+public class DecimalUtilsTest extends CudfTestBase {
+    @Test
+    public void testOutOfBounds() {
+        try (ColumnView cv = ColumnVector.fromDecimals(
+                new BigDecimal("-1E+3"),
+                new BigDecimal("1E+3"),
+                new BigDecimal("9E+1"),
+                new BigDecimal("-9E+1"),
+                new BigDecimal("-91"));
+             ColumnView expected = ColumnVector.fromBooleans(true, true, false, false, true);
+             ColumnView result = DecimalUtils.outOfBounds(cv, 1, -1)) {
+            assertColumnsAreEqual(expected, result);
+        }
+    }
+}