added hints

hints.txt

+-a pipeline needs to be a stage, too, to allow the composition of stages
+-instead of using work-stealing, sort the input in desc order to process the most computationally intensive elements first (load-balancing)
+-for a novice programmer, it is difficult to select the best choice and combination of patterns to maximize performance
+-
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necessary stage types.txt

+[conditional stages]
+-switch (more general than if)
+
+[split and join stages]
+-distributor
+	-necessary to distribute tasks to multiple threads
+-merge
+	-necessary to merge multiple tcp input streams to a single one
+
+[trigger-based stages]
+-aggregation
+	-necessary for trace aggregation
+-cache
+	-necessary to measure performance without being influenced by I/O delay
+
+[stages with internal states]
+-counting
+	-necessary to measure the throughput with multiple threads
+
+[]
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