Bugfix in strategy generation for multi-objective value iteration (Pareto curve).

Caused by mix of min/max objectives.

Reported on forum:
https://groups.google.com/d/msgid/prismmodelchecker/fb293745-a8ca-482c-a363-93a71a032c92o%40googlegroups.com?utm_medium=email&utm_source=footer

prism/src/sparse/PS_NondetMultiObj.cc

@@ -440,20 +440,13 @@ JNIEXPORT jdoubleArray __jlongpointer JNICALL Java_sparse_PrismSparse_PS_1Nondet
 							if (adv[i] == -1) {
 								adv[i] = j;
 							} else {
-								// otherwise it depends whether we're doing min or max
-								// (but sometimes min is max with negative rewards)
-								bool minAdv = min ? d1>0 : d1<0;
-								// for max, only remember strictly better choices
-								// (this resolves problems with end components)
-								// (note use of absolute values because values may be negative)
-								if (!minAdv) {
-									if (fabs(d1)>fabs(soln[i])) {
-										adv[i] = j;
-									}
-								}
-								// for min, always store the value
-								// (in fact, could do it at the end of value iteration, but we don't)
-								else {
+								// normally, we extract optimal choice differently for max
+								// (only remember strictly better choices)
+								// (which resolves problems with end components)
+								// but here it's hard to know when it is max, due to the
+								// mix of objectives and some being negated
+								// so we just always only pick strictly better ones
+								if ((min&&(d1<soln[i])) || (!min&&(d1>soln[i]))) {
 									adv[i] = j;
 								}
 							}