[SYSTEMDS-3765] Fix time displacement through function hoisting

This patch fixes issues with time() functions which are used to
measure execution time of parts of a program. When these functions
were used in expressions (e.g., print string concatenation) the normal
DAG compilation might move them before the operation that was actually
measured. Similar to DML function calls, we now hoist these time
functions out of expressions.

src/main/java/org/apache/sysds/parser/StatementBlock.java

@@ -595,6 +595,13 @@ else if( expr instanceof BuiltinFunctionExpression ) {
 			Expression[] clexpr = lexpr.getAllExpr();
 			for( int i=0; i<clexpr.length; i++ )
 				clexpr[i] = rHoistFunctionCallsFromExpressions(clexpr[i], false, tmp, prog);
+			if( !root && lexpr.getOpCode()==Builtins.TIME ) { //core time hoisting
+				String varname = StatementBlockRewriteRule.createCutVarName(true);
+				DataIdentifier di = new DataIdentifier(varname);
+				di.setDataType(lexpr.getDataType());
+				di.setValueType(lexpr.getValueType());
+				tmp.add(new AssignmentStatement(di, lexpr, di));
+			}
 		}
 		else if( expr instanceof ParameterizedBuiltinFunctionExpression ) {
 			ParameterizedBuiltinFunctionExpression lexpr = (ParameterizedBuiltinFunctionExpression) expr;
@@ -612,7 +619,7 @@ else if( expr instanceof FunctionCallIdentifier ) {
 			FunctionCallIdentifier fexpr = (FunctionCallIdentifier) expr;
 			for( ParameterExpression pexpr : fexpr.getParamExprs() )
 				pexpr.setExpr(rHoistFunctionCallsFromExpressions(pexpr.getExpr(), false, tmp, prog));
-			if( !root ) { //core hoisting
+			if( !root ) { //core fcall hoisting
 				String varname = StatementBlockRewriteRule.createCutVarName(true);
 				DataIdentifier di = new DataIdentifier(varname);
 				di.setDataType(fexpr.getDataType());

src/test/java/org/apache/sysds/test/functions/rewrite/RewriteHoistingTimeTest.java

@@ -19,6 +19,7 @@
 
 package org.apache.sysds.test.functions.rewrite;
 
+import org.junit.Assert;
 import org.junit.Test;
 import org.apache.sysds.common.Types.ExecMode;
 import org.apache.sysds.common.Types.ExecType;
@@ -43,9 +44,14 @@ public void setUp() {
 	}
 
 	@Test
-	public void testTimeHoisting() {
+	public void testTimeHoistingCP() {
 		test(TEST_NAME1, ExecType.CP);
 	}
+
+	@Test
+	public void testTimeHoistingSpark() {
+		test(TEST_NAME1, ExecType.SPARK);
+	}
 
 	private void test(String testname, ExecType et)
 	{
@@ -58,11 +64,15 @@ private void test(String testname, ExecType et)
 
 			String HOME = SCRIPT_DIR + TEST_DIR;
 			fullDMLScriptName = HOME + testname + ".dml";
-			programArgs = new String[] { "-explain", "-args",
+			programArgs = new String[] {"-args",
 				String.valueOf(rows), String.valueOf(cols) };
-
-			//FIXME need to hoist time() out of expression similar to function calls
-			runTest(true, false, null, -1); 
+
+			//test that time is not executed before 1k-by-1k rand
+			setOutputBuffering(true);
+			String out = runTest(true, false, null, -1).toString();
+			double time = Double.parseDouble(out.split(";")[1]);
+			System.out.println("Time = "+time+"s");
+			Assert.assertTrue(time>0.001);
 		}
 		finally {
 			resetExecMode(platformOld);

src/test/scripts/functions/rewrite/RewriteTimeHoisting.dml

@@ -22,5 +22,5 @@
 t1 = time();
 X = rand(rows=$1, cols=$2);
 
-print("time = "+(time()-t1)/1e9+"s"+" "+sum(X));
+print(";"+(time()-t1)/1e9+";"+" "+sum(X));