CS 366 - Vector Processing with SPIM

Due: Wednesday December 4, 2002 at 11:59 pm

This project may be done in groups of two or three students. Your program must clearly list the names and email addresses of all members of your group.

Each student must electronically submit his/her own assignment using the UNIX turnin command on the CS Department's computers. Use the project name of spim2 with the turnin command.

This program is to be written in assembly language that will run under the SPIM/XPSIM software. This program must use functions under the conventions described for the MIPS machine. This program will also use the base displacement addressing mode for access to the vectors. These vectors will be vectors in 3 dimensions: x, y and z. The vectors will be written using the parenthesized notation of (i, j, k) where i is the coefficent in the x direction, j is the coefficent in the y direction and k is the coefficent in the z direction. This program will only use integer coefficents.

In addition to input and output, the program will perform the following operations:

Cross Product
Dot Product
Vector Addition
Scalar Multiplication

Each vector is to be maintained as a "structure" of three integer values. This structure will use the base displacement addressing mode to access the different coefficents of the vector. Assume the register $4 has the address of the structure, the x coefficent will be accessed using 0($4), the y coefficent will be accessed by using 4($4) and the z coefficent will be accessed by using 8($4).

The program is to maintain three vector in three structures as described above. Failure to do so will result in a grade of zero for the assignment. These vectors will all be initialized to the value of (0, 0, 0) when the program starts. We shall refer to these vectors as A, B and C. The operations of Dot Product and Scalar Multiplication both use a scalar value that we shall refer to as S. The scalar value will also be an integer value. The usage of these three vectors and the scalar for these operations is:

Cross Product C <- A x B
Dot Product S <- A . B
Vector Addition C <- A + B
Scalar Multiplication C <- S(A)

This program is to run in a loop. Each time though the loop the following prompt should appear. Note the values i, j, k, m, n, o, p, q and r should be replaced with the actual coefficents of the vectors A, B and C.

	The current vector values are:
	   A: (i, j, k)
	   B: (m, n, o)
	   C: (p, q, r)
	
	Select one of the following operations:
	   1. Change value for vector A
	   2. Change value for vector B
	   3. Compute Cross Product
	   4. Compute Dot Product
	   5. Compute Vector Addition
	   6. Compute Scalar Multiplication
	   7. List information about this program's authors
	   8. Exit the program
	
	Enter choice:

If a invalid choice is given (outside of the range from 1 to 8), print an error message and reprompt.
When option 1 or 2 is selected (Change value for vector A or B), this program is to call a function with the proper parameter values and then give the following prompt:
```
	Select one of the following
	   1. Change vector to the current value of vector A
	   2. Change vector to the current value of vector B
	   3. Change vector to the current value of vector C
	   4. Input new coefficent values
	   5. Leave vector values unchanged
	
	Enter choice:
```
The same function is to called for either option. Based on the choice entered, the function will perform the proper task. The addresses of the vectors A, B and C must be passed as parameters as must the address of the vector to be changed (note: this means that the address of either A or B will be passed twice). If option 4 (Input new values) is selected, prompt the user for three integer values (or call another function that prompt for three integers or perhaps call another function three times that will prompt for a single integer each time). After the function completes, redisplay the main prompt.
When option 3, 4, 5 or 6 is selected, call a function to perform the task, print out the result, return from the function and redisplay the main prompt. Each of this functions must pass the address of the needed vectors as parameters. The operation of Scalar Multiplication requires use of a integer value. This function must prompt for this integer value (or call another function to prompt for the integer value). The functions for Cross Product, Vector Addition and Scalar Multiplication must update the vector C whose address must be supplied via a parameter.
When option 7 is selected, call a function that will print out the names and email addresses of each person in your group and that the program was created for CS 366. After the function completes, redisplay the main prompt.
When option 8 is selected, stop executing the program.

Your program must be well commented and should use blank lines to separate logical sections of your code. Your program must have a large comment at the top of the program describing what the program does and who wrote the program. Also each function in your program must have a large comment at its beginning stating the purpose of the function and what is in each parameter and return value and where each parameter and return value is implemented (i.e. in a register or on the stack. If a register is used, specify which register is being used).

All data items that are being used by any function must be passed to that function via a parameter. All data items that are being returned from a function must be returned using the specified return registers or via a pass-by-reference parameter. This means that all access to data section is forbidden except in the main section of your program. Any program that violates this will receive a grade of zero for the assignment. There is one exception to this rule static textual output can be accessed directly from the data section in any function. Examples of "static textual output" include prompts for input and output used to make output of data more readable.

Alternative Register Names in SPIM

This is from Figure 9.9 in the Goodman&Miller text
Register Name	Alternative Name	Description
$0		the value 0
$1	$at	reserved by the assembler
$2 - $3	$v0 - $v1	expression evaluation and function results
$4 - $7	$a0 - $a3	the first four parameters - not preserved across procedure calls
$8 - $15	$t0 - $t7	temporaries - not preserved across procedure calls
$16 - $23	$s0 - $s7	saved values - preserved across procedure calls
$24 - $25	$t8 - $t9	temporaries - not preserved across procedure calls
$26 - $27	$k0 - $k	reserved for use by the operating system
$28	$gp	global pointer
$29	$sp	stack pointer
$30	$s8	saved value - preserved across procedure calls
$31	$ra	return address
$f0 - $f2		floating point function results
$f4 - $f10		temporaries - not preserved across procedure calls
$f12 - $f14		the first two floating point parameters - not preserved across procedure calls
$f16 - $18		temporaries - not preserved across procedure calls
$f20 - $f30		saved values - preserved across procedure calls

Input and Output in SPIM

I/O is done in SPIM using the syscall opcode. For each I/O operation, a specific value is placed in the $2 register (also referred to as $v0). Depending on the I/O operation to be performed, other registers may be involved. The following table lists the possible syscall services.

Service	System Call Code placed in $2/$v0	Arguments	Results
print_int	1	$a0 = integer
print_float	2	$f12 = float
print_double	3	$f12 = double
print_string	4	$a0 = address of string
read_int	5		integer (in $v0)
read_float	6		float (in $f0)
read_double	7		double (in $f0)
read_string	8	$a0 = address of string buffer $a1 = length of string buffer
sbrk	9	$a0 = amount	address (in $v0)
exit	10

The print_string service expects the address to start a null-terminated character string. The directive .asciiz creates a null-terminated character string.
The read_int, read_float and read_double services read an entire line of input up to and including the newline character.
The read_string service has the same semantices as the UNIX library routine fgets.
- It reads up to n-1 characters into a buffer and terminates the string with a null character.
- If fewer than n-1 characters are in the current line, it reads up to and including the newline and terminates the string with a null character.
The sbrk service returns the address to a block of memory containing n additional bytes. This would be used for dynamic memory allocation.
The exit service stops a program from running.

Spim Input/Output Example Program

The following special characters are used with character strings in SPIM. The special characters follow the C language convention:

Character Encoding Sequence
Newline \n
Tab \t
Double quote \"

Cross Product	C <- A x B
Dot Product	S <- A . B
Vector Addition	C <- A + B
Scalar Multiplication	C <- S(A)