MNEMEE - Electronic Systems - Technische Universiteit Eindhoven

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Memory hierarchy re-use In addition to the copy candidates identified at branches and loops, more copy candidates can be generated by two techniques: • considering both loop-carried and non-loop-carried versions of a copy candidate at loop boundaries, considering different combinations of copy-candidates from different branches as a new copycandidate (“XOR” algorithm). These techniques are explained by examples from the MPEG-4 encoder application. In a re-use graph, the direction of the arrows between copy candidates indicates the direction in which data transfers between them have to occur. For example, consider Figure 25. The bi-directional arrow between @1 and @4 indicates that @4 has to be initialized with data from @1 first, and after it has been accessed, the contents of @4 has to be written back to @1, i.e., it has both loads and stores. The arrow between @1 and @5, on the other hand, is uni-directional, meaning that @5 only has to load data from @1, but nothing has to be written back (because @5 is only read, not written, by accesses in the application). With the simple reuse algorithm, a copy candidate at a higher level always covers all the copy candidates at the levels below it. So, in the example, only @12C would be extracted at the “loop v” level. In reality, it is not always true that such a copy candidate covering all of its children represents the best solution. Sometimes, it can be better to leave out certain children. In this case, the tool has analyzed that there is a possibly better solution at that level that doesn’t cover the write accesses, namely @14C. This is what the more complex algorithm does: it does not only consider copy candidates that are covering all of their children, but also partial combinations. Public Page 48 of 87
Figure 25 - (Pruned) re-use graph of the reconstructed Y-frame demonstrating the results of the XOR re-use identification algorithm. The graph is also no longer a simple tree; it contains re-convergent paths. The later is a sign that the complex reuse analysis algorithm has been at work (the “XOR” algorithm). For instance, @14C does not have just a single parent, as one could expect, but two parents. Next, consider Figure 26. It shows a part of the re-use graph of the Y-frame. Only the accesses in the motion-estimation are considered and the XOR generated copy candidates have been omitted. Yet there are still multiple copy candidates for each level in the syntax tree. This is caused by loop-carried copy-candidates, which have a C postfix in their name. Public Page 49 of 87
Page 1 and 2: Information Societies Technology (I
Page 3 and 4: 9.5. METRICS AND COST FACTORS FOR D
Page 5 and 6: Public Page 5 of 87
Page 7 and 8: 4. Preface The main objectives of t
Page 9 and 10: 6. Introduction Multimedia applicat
Page 11 and 12: Figure 2 - Preliminary MNEMEE sourc
Page 13 and 14: modelled with an FSM-based SADF, on
Page 15 and 16: analyzing the basic operations of t
Page 17 and 18: Figure 5 - SDFG-based MP-SoC design
Page 19 and 20: Figure 6 - H.263 encoder mapped ont
Page 21 and 22: transitions reflect possible next s
Page 23 and 24: parameters is modified, the applica
Page 25 and 26: There is however one problem with u
Page 27 and 28: 7.6. FSM-based SADF-based multi-pro
Page 29 and 30: 8. Statically allocated data storag
Page 31 and 32: Embedded systems differ from genera
Page 33 and 34: Plasma), etc., is enabled by compre
Page 35 and 36: One of the most important developme
Page 37 and 38: The Atomium/Analysis version includ
Page 39 and 40: 8.4.3. Profiling steps Profiling th
Page 41 and 42: Array size [bytes] Number of access
Page 43 and 44: For multimedia application this is
Page 45 and 46: Figure 22 - Data re-use at differen
Page 47: Figure 24 - (Pruned) re-use graph o
Page 51 and 52: has to be refreshed completely, bec
Page 53 and 54: Figure 27 - Assignment of copies (c
Page 55 and 56: information about the platform, esp
Page 57 and 58: 9. Dynamically allocated data stora
Page 59 and 60: combination of DDT implementations.
Page 61 and 62: manager does not know beforehand wh
Page 63 and 64: locked remains allocated and the DM
Page 65 and 66: Improving the performance of the DM
Page 67 and 68: The problem with the aforementioned
Page 69 and 70: 1. Problem 1: Increased complexity
Page 71 and 72: Table 3 - Comparison of different p
Page 73 and 74: Table 4 - Profiling information sto
Page 75 and 76: Figure 40 - Maximum number of objec
Page 77 and 78: Figure 43 - Utilization of the allo
Page 79 and 80: 10. Conclusions Future multimedia a
Page 81 and 82: [17] Ang, S., Constantinides, G., L
Page 83 and 84: [34] MPEG-2. Generic coding of movi
Page 85 and 86: [65] SGI. Standard template library
Page 87: 12. Glossary ANL Atomium analysis D

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