Created
April 7, 2017 19:12
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Compressed Sparse Row (CSR) Matrix
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// https://en.wikipedia.org/wiki/Sparse_matrix#Compressed_sparse_row_.28CSR.2C_CRS_or_Yale_format.29 | |
function csr(matrix) { | |
const A = []; | |
const IA = [0]; | |
const JA = []; | |
const nnz = []; | |
for (const [ index, row ] of matrix.entries()) { | |
nnz[index] = 0; | |
for (const [ column, value ] of row.entries()) { | |
if (value !== 0) { | |
A.push(value); | |
JA.push(column); | |
nnz[index] += 1; | |
} | |
} | |
IA[index + 1] = IA[index] + nnz[index]; | |
} | |
return [ A, IA, JA ]; | |
} | |
function uncsr([ A, IA, JA ]) { | |
const result = []; | |
let count = 0; | |
for (const [ index, value ] of IA.entries()) { | |
if (index < IA.length - 1) { | |
result[index] = []; | |
const row = JA.slice(value, IA[index + 1]); | |
for (const pos of row) { | |
result[index][pos] = A[count]; | |
count += 1; | |
} | |
} | |
} | |
return result; | |
} |
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