--- ray/src/rt/RcontribSimulManager.cpp	2025/10/16 23:14:31	2.13
+++ ray/src/rt/RcontribSimulManager.cpp	2025/10/17 01:15:53	2.14
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: RcontribSimulManager.cpp,v 2.13 2025/10/16 23:14:31 greg Exp $";
+static const char RCSid[] = "$Id: RcontribSimulManager.cpp,v 2.14 2025/10/17 01:15:53 greg Exp $";
 #endif
 /*
  *  RcontribSimulManager.cpp
@@ -52,6 +52,8 @@ struct RowAssignment {
 	uint32			ac;		// accumulation count
 };
 
+static const char	ROW_DONE[] = "ROW FINISHED\n";
+
 // Get format identifier
 const char *
 formstr(int f)
@@ -625,8 +627,8 @@ RcontribSimulManager::ComputeRecord(const FVECT orig_d
 		return 0;
 	}
 	if (nkids > 0) {			// in parent process?
-		int	k = GetChild();		// updates output rows
-		if (k < 0) return -1;		// can't really happen
+		int	k = GetChild(false);	// updates output rows
+		if (k < 0) return -1;		// someone died?
 		RowAssignment	rass;
 		rass.row = kidRow[k] = rInPos++;
 		rass.ac = accum;
@@ -671,35 +673,40 @@ RcontribSimulManager::GetChild(bool forceWait)
 		return -1;
 						// take inventory
 	int	pn, n = 0;
-	fd_set	writeset, errset;
-	FD_ZERO(&writeset); FD_ZERO(&errset);
+	fd_set	readset, errset;
+	FD_ZERO(&readset); FD_ZERO(&errset);
 	for (pn = nkids; pn--; ) {
 		if (kidRow[pn] < 0) {		// child already ready?
 			if (forceWait) continue;
 			return pn;		// good enough
 		}
-		FD_SET(kid[pn].w, &writeset);	// will check on this one
-		FD_SET(kid[pn].w, &errset);
-		if (kid[pn].w >= n)
-			n = kid[pn].w + 1;
+		FD_SET(kid[pn].r, &readset);	// will check on this one
+		FD_SET(kid[pn].r, &errset);
+		if (kid[pn].r >= n)
+			n = kid[pn].r + 1;
 	}
 	if (!n)					// every child is idle?
 		return -1;
 						// wait on "busy" child(ren)
-	while ((n = select(n, NULL, &writeset, &errset, NULL)) <= 0)
+	while ((n = select(n, &readset, NULL, &errset, NULL)) <= 0)
 		if (errno != EINTR) {
 			error(SYSTEM, "select call failed in GetChild()");
 			return -1;
 		}
+	char	buf[sizeof(ROW_DONE)] = "X";
 	pn = -1;				// get flags set by select
 	for (n = nkids; n--; )
 		if (kidRow[n] >= 0 &&
-				FD_ISSET(kid[n].w, &writeset) |
-				FD_ISSET(kid[n].w, &errset)) {
+				FD_ISSET(kid[n].r, &readset) |
+				FD_ISSET(kid[n].r, &errset)) {
+						// check for error
+			if (FD_ISSET(kid[n].r, &errset) ||
+					read(kid[n].r, buf, sizeof(ROW_DONE)) <= 0 ||
+					memcmp(buf, ROW_DONE, sizeof(ROW_DONE)))
+				return -1;
 						// update output row counts
-			if (!FD_ISSET(kid[n].w, &errset))
-				UpdateRowsDone(kidRow[n]);
-			kidRow[n] = -1;		// flag it available
+			UpdateRowsDone(kidRow[n]);
+			kidRow[n] = -1;		// flag child available
 			pn = n;
 		}
 	return pn;
@@ -750,6 +757,9 @@ RcontribSimulManager::RunChild()
 
 		if (ComputeRecord(vecList) <= 0)
 			exit(1);
+						// signal this row is done
+		if (write(1, ROW_DONE, sizeof(ROW_DONE)) != sizeof(ROW_DONE))
+			exit(1);
 	}
 	if (nr) {
 		error(SYSTEM, "read error in child process");
@@ -775,12 +785,12 @@ RcontribSimulManager::StartKids(int n2go)
 	fflush(stdout);				// shouldn't use, anyway
 	while (nkids < n2go) {
 		kid[nkids] = sp_inactive;
-		kid[nkids].w = dup(1);
-		kid[nkids].flags |= PF_FILT_OUT;
 		int	rv = open_process(&kid[nkids], NULL);
 		if (!rv) {			// in child process?
-			while (nkids-- > 0)
+			while (nkids-- > 0) {
+				close(kid[nkids].r);
 				close(kid[nkids].w);
+			}
 			free(kid); free(kidRow);
 			kid = NULL; kidRow = NULL;
 			RunChild();		// should never return