[SYSTEMDS-2944] Fix incorrect nnz propagation of unary hops

This patch fixes an issue identified in #1862, where despite no NaNs,
the numbers of sum(X!=0) and sum(X==0) did not add up to the number
of cells because we incorrectly propagated the nnz for X and rewrote
sum(X!=0) to obtain the nnz from the metadata, while sum(X==0) was
actually executed.

src/main/java/org/apache/sysds/hops/UnaryOp.java

@@ -558,13 +558,10 @@ else if(_op == OpOp1.TYPEOF || _op == OpOp1.DETECTSCHEMA || _op == OpOp1.COLNAME
 		{
 			// If output is a Matrix then this operation is of type (B = op(A))
 			// Dimensions of B are same as that of A, and sparsity may/maynot change
+			// note: round, sin, cos can introduce new zeros for non-zero inputs
 			setDim1( input.getDim1() );
 			setDim2( input.getDim2() );
-			// cosh(0)=cos(0)=1, acos(0)=1.5707963267948966
-			if( _op==OpOp1.ABS || _op==OpOp1.SIN || _op==OpOp1.TAN  
-				|| _op==OpOp1.SINH || _op==OpOp1.TANH
-				|| _op==OpOp1.ASIN || _op==OpOp1.ATAN
-				|| _op==OpOp1.SQRT || _op==OpOp1.ROUND || _op==OpOp1.SPROP
+			if( _op==OpOp1.ABS || _op==OpOp1.SQRT || _op==OpOp1.SPROP
 				|| _op==OpOp1.COMPRESS || _op==OpOp1.DECOMPRESS || _op==OpOp1.LOCAL) //sparsity preserving
 			{
 				setNnz( input.getNnz() );

src/test/java/org/apache/sysds/test/functions/misc/NNZPropagationTest.java

@@ -0,0 +1,67 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.sysds.test.functions.misc;
+
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.Map;
+
+import org.apache.sysds.runtime.matrix.data.MatrixValue.CellIndex;
+import org.apache.sysds.test.AutomatedTestBase;
+import org.apache.sysds.test.TestConfiguration;
+import org.apache.sysds.test.TestUtils;
+
+public class NNZPropagationTest extends AutomatedTestBase 
+{
+	private final static String TEST_NAME1 = "nnzUnary";
+	private final static String TEST_DIR = "functions/misc/";
+	private final static String TEST_CLASS_DIR = TEST_DIR + NNZPropagationTest.class.getSimpleName() + "/";
+
+	@Override
+	public void setUp() {
+		TestUtils.clearAssertionInformation();
+		addTestConfiguration( TEST_NAME1, new TestConfiguration(TEST_CLASS_DIR, TEST_NAME1, new String[]{"R"}));
+	}
+
+	@Test
+	public void testNnzUnary() {
+		runExistsTest(TEST_NAME1, 14967, 5033);
+	}
+
+	private void runExistsTest(String testName, int expNNZ, int expNZ) {
+		TestConfiguration config = getTestConfiguration(testName);
+		loadTestConfiguration(config);
+		String HOME = SCRIPT_DIR + TEST_DIR;
+		fullDMLScriptName = HOME + testName + ".dml";
+		programArgs = new String[]{"-explain","-args", output("R") };
+
+		//run script and compare output
+		runTest(true, false, null, -1); 
+
+		//compare results
+		Map<CellIndex, Double> ret = readDMLMatrixFromOutputDir("R");
+		Double nnonzero = ret.get(new CellIndex(1,1));
+		Double nzero = ret.get(new CellIndex(2,1));
+		Assert.assertEquals(expNNZ, nnonzero, 1e-14);
+		Assert.assertEquals(expNZ, nzero, 1e-14);
+	}
+}

src/test/scripts/functions/misc/nnzUnary.dml

@@ -0,0 +1,25 @@
+#-------------------------------------------------------------
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+#
+#-------------------------------------------------------------
+
+X = round(rand(rows=10000, cols=2, min=-2, max=2, seed=7))
+R = as.matrix(list(sum(X!=0), sum(X==0)))
+write(R, $1);
+