Matrix CSR Single Row Storage Span Tool

Description

Select row and return its start, next pointer as endExclusive, and their difference as count.

Compressed sparse-row storage locates each row between two pointer offsets. Repeated pointers represent empty rows, while a missing column search needs a distinct sentinel.

Select row and return its start, next pointer as endExclusive, and their difference as count.

When to use this tool

Use Matrix CSR Single Row Storage Span when you need one CSR row span or local lookup.

How to use the tool and how it works

Enter rowPointers, row. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read start, endExclusive, count. Use the output convention below.

Require rowPointers starting at zero, nonnegative and nondecreasing, with at least two entries. Select row and return its start, next pointer as endExclusive, and their difference as count.^[1]

Input field	Meaning and units	Accepted input
rowPointers	Row Pointers	Required. Array of safe integer; maximum items 256.
row	Row	Required. Safe integer; minimum 0.

Output field	Interpretation	Returned shape
start	Start	Required. Safe integer.
endExclusive	End boundary excluded from the represented span.	Required. Safe integer.
count	Count	Required. Safe integer.

json

{
  "input": {
    "rowPointers": [
      0,
      2,
      2,
      5
    ],
    "row": 1
  },
  "output": {
    "start": 2,
    "endExclusive": 2,
    "count": 0
  }
}

Limitations and assumptions

This validates the pointer layout only; column indices, value-array lengths, and duplicate entries are not checked.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Validate pointer, column, and value arrays together, including shape, sorting, and duplicate-entry policy.

References

Calculation and input contract: matrix/matrix-csr-single-row-storage-span — tool.io

Similar or alternative tools

Matrix CSR Row Column Local Offset
Search columnIndices only within [rowStart, rowEnd).
Matrix Symmetric Band Storage Offset
Use distance = column - row.