Exercise 1 The HeapManager in this chapter implements a first-fit mechanism. It uses the first block on the free list that is at least as large as the requested size. Another fairly simple mechanism is called best-fit. As you might guess, the idea is to search the free list for a sufficiently large block that is as close to the requested size as possible. If there is an exact fit on the free list, the best-fit mechanism can stop the search early. Otherwise, it has to search all the way to the end of the free list. This has the advantage that it does not break up large blocks unnecessarily. For example, if there is an exact fit somewhere on the list, the best-fit mechanism will find one, so it will not have to split a block at all. Implement a version of HeapManager with a best-fit mechanism. Start with a renamed copy of the HeapManager class, and then modify the allocate method to implement a best-fit search. (The code for HeapManager is available on the Web site for this book. It includes the coalescing version of deallocate, which is the one you should use.) After this has been tested and works, find a simple sequence of operations for which your best-fit manager succeeds while the first-fit one fails, Hint: There is a sequence that begins like this: mm = new HeapManager (new int [7]); int a mm.allocate (2); int b mm. allocate (1); inte mm. allocate (1); mm.deallocate (a); mm.deallocate (c); By extending this sequence with just two more calls to mm. allocate, you can get something that will succeed for best-fit and fail for first-fit. Although best-fit is often a better placement strategy than first-fit, there are examples for which it is worse. Find a simple sequence of operations for which the first-fit manager succeeds while your best-fit one fails. Hint: There is a sequence that begins like this: mim = new HeapManager (new int [11]); a mm. allocate (4); b = mm. allocate (1); c mm. allocate (3); mm.deallocate (a); mm.deallocate (c); By extending this sequence with just three more calls to mm. allocate, you can get

Exercise 1 The HeapManager in this chapter implements a first-fit mechanism. It uses the first block on the free list that is at least as large as the requested size. Another fairly simple mechanism is called best-fit. As you might guess, the idea is to search the free list for a sufficiently large block that is as close to the requested size as possible. If there is an exact fit on the free list, the best-fit mechanism can stop the search early. Otherwise, it has to search all the way to the end of the free list. This has the advantage that it does not break up large blocks unnecessarily. For example, if there is an exact fit somewhere on the list, the best-fit mechanism will find one, so it will not have to split a block at all. Implement a version of HeapManager with a best-fit mechanism. Start with a renamed copy of the HeapManager class, and then modify the allocate method to implement a best-fit search. (The code for HeapManager is available on the Web site for this book. It includes the coalescing version of deallocate, which is the one you should use.) After this has been tested and works, find a simple sequence of operations for which your best-fit manager succeeds while the first-fit one fails, Hint: There is a sequence that begins like this: mm = new HeapManager (new int [7]); int a mm.allocate (2); int b mm. allocate (1); inte mm. allocate (1); mm.deallocate (a); mm.deallocate (c); By extending this sequence with just two more calls to mm. allocate, you can get something that will succeed for best-fit and fail for first-fit. Although best-fit is often a better placement strategy than first-fit, there are examples for which it is worse. Find a simple sequence of operations for which the first-fit manager succeeds while your best-fit one fails. Hint: There is a sequence that begins like this: mim = new HeapManager (new int [11]); a mm. allocate (4); b = mm. allocate (1); c mm. allocate (3); mm.deallocate (a); mm.deallocate (c); By extending this sequence with just three more calls to mm. allocate, you can get

C++ Programming: From Problem Analysis to Program Design

8th Edition

ISBN:9781337102087

Author:D. S. Malik

Publisher:D. S. Malik

Chapter18: Stacks And Queues

Section: Chapter Questions

Problem 16PE: The implementation of a queue in an array, as given in this chapter, uses the variable count to...

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