Assembly Assignment 6 - Lottery

Transcription

1 Assembly Assignment 6 - Lottery Valdemar Örn Erlingsson Pseudo-Code Again, I write in a language I know very well, C++. Writing real code lets me test all functionality before I start. #include <iostream> using namespace std; int getrandom(); void int line[5]; int getrandom() { int r = rand(); //Fetch a random number r = r % 40; // Make sure number is in range r = r+1; // Add one to make range return r; } void getline() { L0: line[0] = getrandom(); //Fetch a random number L1: line[1] = getrandom(); // Note how I roll out the comparison for this part. // Only 5 numbers, easier to handle like // this in assembly, then to use loops! if (line[1] == line[0]) goto L1; L2: line[2] = getrandom(); if (line[2] == line[0]) goto L2; if (line[2] == line[1]) goto L2;

2 L3: L4: line[3] = getrandom(); if (line[3] == line[0]) goto L3; if (line[3] == line[1]) goto L3; if (line[3] == line[2]) goto L3; line[4] = getrandom(); if (line[4] == line[0]) if (line[4] == line[1]) if (line[4] == line[2]) if (line[4] == line[3]) } // Print a line of numbers cout << "\n" << line[0] << "\t" << line[1]; cout << "\t" << line[2] << "\t" << line[3] << "\t" << line[4]; int main() { srand ( time(null) ); // Seed the random generator // Create and print five lines // Print the winning line and bonus number cout << "\n\nwinning numbers (Bonus number)"; int bonus; Bonus: bonus = getrandom(); if (bonus == line[0]) if (bonus == line[1]) if (bonus == line[2]) if (bonus == line[3]) if (bonus == line[4]) cout << "\t(" << bonus << ")\n"; } return 0;

3 Assembly code START ORG $1000 BRA MAIN LINE DS.W 5 * Storage for the numbers of every line SPACE DC.B ' ',0 TAB DC.B 9,0 LEFTBR DC.B '(',0 RIGHTBR DC.B ')',0 WINNER DC.B 'Tonights lottery numbers (Bonus number)',0 NOP MACRO LEA SPACE,A1 * Print blank line MOVE.B #13,D0 ENDM MACRO LEA TAB,A1 * Print tab character MOVE.B #14,D0 ENDM * Random number generator * NextPRN Ninc0 MOVEQ #$AF-$100,d1 MOVEQ #18,d2 MOVE.l d6,d0 ADD.l d0,d0 BCC.s Ninc1 * set EOR value * do this 19 times * get current * shift left 1 bit * branch if bit 32 not set Ninc1 EOR.b d1,d0 DBF d2,ninc0 * loop * do galois LFSR feedback MOVE.l d0,d6 MOVE.l d0,d1 RTS * save back to seed word * Save also to d1 for displaying NextPRN SWAP d1 * the top 16 bits are "a bit more random" * than the lower 16 bits... :) MOVE.w d1,d2 MOVE.l d2,d1 * get rid of upper 16 bits MOVEQ #40,d2 DIVU d2,d1 * divide by 40, remainder (modulus) in * upper 16 bits SWAP d1 * put remainder in lower 16 bits MOVE.w d1,d2 MOVE.l d2,d1 * get rid of upper 16 bits ADDI.L #1,d1 RTS * randum number stored in d1

4 L0 L1 LEA LINE,A6 * Load address of line into A6 * Use A4 as working pointer BEQ L1 L2 BEQ L2 BEQ L2 ADDQ #4,A5 L3 BEQ L3 BEQ L3 CMP (A5),D1 * Compare to (2) BEQ L3 ADDQ #6,A5 L4

5 CMP (A5),D1 * Compare to (2) CMP (A5),D1 * Compare to (3) ADDQ #8,A5 * Print the entire line MOVEQ #2,D2 RTS

6 MAIN seed MOVE.B #8,D0 MOVE d1,d6 * Fetch seconds from midnight for random LEA WINNER,A1 * Print "Tonights lottery numbers.." MOVE.B #13,D0 * Get the winning line BONUS CMP (A5),D1 * Compare to (2) CMP (A5),D1 * Compare to (3) CMP (A5),D1 * Compare to (4) ADDQ #8,A5 MOVE D1,D6 * Keep bonus number in D6 LEA LEFTBR,A1 * Print left bracket MOVE.B #14,D0 MOVE D6,D1 * Print the number MOVE.L #3,D0

7 LEA RIGHTBR,A1 * Print left bracket MOVE.B #13,D0 MOVE.B #9,D0 Halt Simulator END START Notes The code contains alot of repetitions. I do this rather than use loops at some points because it is easier to implement. Also, although code size is larger, execution is faster this way, so it's not all bad. The random number generator was found at I use Trap #8 as the first seed (returns time from midnight). This is decent, but it does not give *good* randomness. Although not specifially mentioned in the project, I have added a check to make sure each number only appears once in every line. This feature takes up almost half the program code, but the same code is repeated several times.