fix(optim): refuse non-finite bounds in differential evolution

Assisted-by: DeepSeek V4.1 Flash

optim/devolution.go

@@ -58,8 +58,12 @@ func MinimiseDifferentialEvolution(f func(*core.Array) (float64, error),
 		return nil, 0, base.Errf("%s: complex bounds are not supported", name)
 	}
 	for i := range n {
-		if !(upper.FloatAt(i) > lower.FloatAt(i)) {
-			return nil, 0, base.Errf("%s: bound %d runs from %g to %g", name, i, lower.FloatAt(i), upper.FloatAt(i))
+		lo, up := lower.FloatAt(i), upper.FloatAt(i)
+		// An infinite side has no uniform draw: the population would be
+		// born NaN and the best point would come back NaN with no error,
+		// so a non-finite bound is degenerate exactly as a crossed one is.
+		if math.IsNaN(lo) || math.IsNaN(up) || math.IsInf(lo, 0) || math.IsInf(up, 0) || !(up > lo) {
+			return nil, 0, base.Errf("%s: bound %d runs from %g to %g", name, i, lo, up)
 		}
 	}
 	pop := opts.Population