ECE 2035 Programming HW/SW Systems Fall problems, 5 pages Exam Three 20 November 2013

Transcription

1 Instructions: This is a closed book, closed note exam. Calculators are not permitted. If you have a question, raise your hand and I will come to you. Please work the exam in pencil and do not separate the pages of the exam. For maximum credit, show your work. Good Luck! Your Name (please print) total

2 Problem 1 (2 parts, 24 points) Heap and Hash Table Part A (16 points) Consider an open hash table composed of a four-bucket table, with each bucket containing a variable length list. Each list entry has three slots <key, value, next> corresponding to the three word groupings in the entries section. The hash function is key mod four. Inserted entries are appended to the end of a bucket list. Deallocated entries are maintained on a LIFO free list. When the free list is empty, new entry objects are allocated from heap memory. Accesses are listed as <op, key, [value]>. Simulate the access trace below and draw the ending state. Assume the hash table already contains 3 elements as shown and the heap pointer is initially 5052 and the free pointer is initially 0. Heap Pointer 5052 Free List 0000 Buckets Entries Hash Table Access Trace # op key value 1 insert remove 5005 n/a 3 insert insert Part B (8 points) Consider a different hash table that uses 11 buckets, each containing a list of entries. The hash table contains a total of 594 entries evenly distributed across the hash table buckets. Assume that computing the hash function takes an average of four operations and comparing two keys takes an average of six operations. Ignore effects of spatial and temporal reference locality. Suppose that twothirds of keys looked up are found in the hash table and one-third are not found. How many operations would be required for the average lookup in the hash table if each bucket list is unsorted versus sorted? number of operations when each bucket list is unsorted: number of operations when each bucket list is sorted: 2

3 Problem 2 (6 parts, 24 points) Complete the following C code by following the steps below: int Inc(int x) return(x+7); int Dec(int y) return(y-5); typedef int ScoreCard(int points, int penalties) { Function Pointers, Interrupts, Concurrency UpdatePts(points, ); /* part B */...rest of ScoreCard's body... Part A (6 points) Create a local variable, called Update, in ScoreCard that is a function pointer that points to Dec if penalties>0 and to Inc otherwise. Define the function pointer type with typedef. Part B (2 points) Pass this function pointer to the subroutine UpdatePts as its second parameter. Part C (3 points) Suppose Inc and Dec are defined in instruction memory starting at the following addresses: Inc: 1000 Dec: 1200 What are the values of the two input parameters to UpdatePts if ScoreCard(56, 2) is called? Value of Parameter 1: Value of Parameter 2: Part D (4 points) Classify each of the following types of interrupts. Interrupt Asynchronous Synchronous NonMaskable (NMI) Mouse click Divide by zero Ctrl-Alt-Del Page fault Part E (6 points) Name at least 3 items that are private to each thread in a multicore system Part F (3 points) What issue can arise if two threads share a global variable? 3

4 Problem 3 (4 parts, 30 points) Heap Management Below is a snapshot of heap storage. The heap has been allocated contiguously beginning at address 6000, with no gaps between objects using a heap manager implemented in C. addr value addr value addr value addr value addr value addr value Below is a portion of the heap manager: L-1 char Heap[HEAPSIZE]; L-2 char *HeapPtr = Heap; L-3 void **FreePtr = NULL; L-4 L-5 void Free(void *ObjectPtr) { L-6 int ObjectSize; L-7 void **ThisPtr = FreePtr; L-8 void **LastPtr = (void **) &FreePtr; L-9 ObjectSize = *(-1 + (int *) ObjectPtr); L-10 L-11 while (ThisPtr!= NULL && ObjectSize > *((int *) ThisPtr - 1)) { L-12 LastPtr = ThisPtr; L-13 ThisPtr = (void **) *ThisPtr; L-14 L-15 * (void **) ObjectPtr = ThisPtr; L-16 *LastPtr = ObjectPtr; L-17 Assume HeapPtr = 6168 and FreePtr = 6080 and FreePtr is located at address Part A: (2 points) Circle all object size words in the snapshot above. Part B: (4 points) List the base addresses of the heap objects that are on the free list in the order they appear on the free list. Part C (4 points) Based on the free list after part B, if an object of size 5 bytes is allocated, what address will be returned? How many bytes of slack (if any) will result? Address: Slack: Part D: (20 points) Suppose the following function call is made: Free(p), where p=6052. Given the snapshot of heap above, what is the value of the following at each of the indicated locations in the code? ThisPtr LastPtr *LastPtr *ObjectPtr ObjectSize at L-10 at L-17 4

5 Problem 4 (7 parts, 22 points) Complete the following C code by following the steps below: typedef struct Stats { float ERA; int RBI; double Salary; struct Stats *Next; Stats; Stats *Team = NULL; void Add_Player(float Pitching, int Runs, double Pay){ Dynamic Allocation on Heap ; /* part B*/ if ( ){ /* part D */ printf( Error: Insufficient space. ); exit(1); ; /* part F*/ ; /* part F*/ Part A (3 pts) Add a local variable called NewPlayer to Add_Player that is a pointer to a Stats object. Part B (4 points) Allocate space for a Stats structure using malloc and make NewPlayer point to the object allocated. Be sure to include appropriate type casting to avoid type errors. Part C (4 points) How many bytes are allocated in Part B for the Stas structure, excluding its size header? Assume a 32-bit system. bytes Part D (3 pts) Fill in the test for whether malloc found enough space which controls the print statement. Part E (4 pts) Initialize the fields (ERA, RBI, Salary) of the newly allocated Stats object to the values of the 3 input parameters (Pitching, Runs, Pay, respectively). Part F (4 points) Push the newly allocated Stats object onto the front of the list of Stats objects pointed to by the global variable Team. 5