Compute Array Index (CAI)

Instruction Syntax

Op Code (Hex) Operand 1 Operand 2 Operand 3 Operand 4
1044 Array index Subscript A Subscript B Dimension
Operand 1: Binary(2) variable scalar.

Operand 2: Binary(2) scalar.

Operand 3: Binary(2) scalar.

Operand 4: Binary(2) constant scalar object or immediate operand.

Description:

This instruction provides the ability to reduce multidimensional array subscript values into a single index value which can then be used in referencing the single-dimensional arrays of the system. This index value is computed by performing the following arithmetic operation on the indicated operands.

ARRAY INDEX = Subscript A + ((Subscript B-1) X Dimension)

The numeric value of the subscript B operand is decreased by 1 and multiplied by the numeric value of the dimension operand. The result of this multiplication is added to the subscript A operand and the sum is placed in the array index operand.

All the operands must be binary with any implicit conversions occurring according to the rules of arithmetic operations documented in Arithmetic Operations. The usual rules of algebra are observed concerning the subtraction, addition, and multiplication of operands.

This instruction provides for mapping multidimensional arrays to single-dimensional arrays. The elements of an array with the dimensions (d1, d2, d3, ..., dn) can be defined as a single-dimensional array with d1*d2*d3*...*dn elements. To reference a specific element of the multidimensional array with subscripts (s1,s2,s3,...sn), it is necessary to convert the multiple subscripts to a single subscript for use in the single-dimensional array. This single subscript can be computed using the following: 

s1+((s2-1)*d1)+(s3-1)*d1*d2)+...+((sn-1)*d*d2*d3*...*dm)
where m = n-1

The CAI instruction is used to form a single index value from two subscript values. To reduce N subscript values into a single index value, N-1 uses of this instruction are necessary.

Assume that S1, S2, and S3 are three subscript values and that D1 is the size of one dimension, D2 is the size of the second dimension, and the D1D2 is the product of D1 and D2. The following two uses of this instruction reduce the three subscripts to a single subscript. 

CAI INDEX, S1, S2, D1      Calculates s1+(s2-1)*d1
CAI INDEX, INDEX, S3, D1D2 Calculates s1+(s2-1)*d1+(s3-1)*d2*d1

Authorization Required

  • None

Lock Enforcement

  • None

Exceptions

  • 06 Addressing
    • 0601 Space Addressing Violation
    • 0602 Boundary Alignment
    • 0603 Range
  • 08 Argument/Parameter
    • 0801 Parameter Reference Violation
  • 0C Computation
    • 0C0A Size
  • 10 Damage Encountered
    • 1004 System Object Damage State
    • 1044 Partial System Object Damage
  • 1C Machine-Dependent
    • 1C03 Machine Storage Limit Exceeded
  • 20 Machine Support
    • 2002 Machine Check
    • 2003 Function Check
  • 22 Object Access
    • 2201 Object Not Found
    • 2202 Object Destroyed
    • 2203 Object Suspended
    • 2208 Object Compressed
    • 220B Object Not Available
  • 24 Pointer Specification
    • 2401 Pointer Does Not Exist
    • 2402 Pointer Type Invalid
  • 2E Resource Control Limit
    • 2E01 User Profile Storage Limit Exceeded
  • 36 Space Management
    • 3601 Space Extension/Truncation
  • 44 Protection Violation
    • 4401 Object Domain or Hardware Storage Protection Violation
    • 4402 Literal Values Cannot Be Changed