BlockMatrix

class pyspark.mllib.linalg.distributed.BlockMatrix(blocks, rowsPerBlock, colsPerBlock, numRows=0, numCols=0)

Represents a distributed matrix in blocks of local matrices.

Parameters

blockspyspark.RDD

An RDD of sub-matrix blocks ((blockRowIndex, blockColIndex), sub-matrix) that form this distributed matrix. If multiple blocks with the same index exist, the results for operations like add and multiply will be unpredictable.

rowsPerBlockint

Number of rows that make up each block. The blocks forming the final rows are not required to have the given number of rows.

colsPerBlockint

Number of columns that make up each block. The blocks forming the final columns are not required to have the given number of columns.

numRowsint, optional

Number of rows of this matrix. If the supplied value is less than or equal to zero, the number of rows will be calculated when numRows is invoked.

numColsint, optional

Number of columns of this matrix. If the supplied value is less than or equal to zero, the number of columns will be calculated when numCols is invoked.

Methods

add(other)	Adds two block matrices together.
cache()	Caches the underlying RDD.
multiply(other)	Left multiplies this BlockMatrix by other, another BlockMatrix.
numCols()	Get or compute the number of cols.
numRows()	Get or compute the number of rows.
persist(storageLevel)	Persists the underlying RDD with the specified storage level.
subtract(other)	Subtracts the given block matrix other from this block matrix: this - other.
toCoordinateMatrix()	Convert this matrix to a CoordinateMatrix.
toIndexedRowMatrix()	Convert this matrix to an IndexedRowMatrix.
toLocalMatrix()	Collect the distributed matrix on the driver as a DenseMatrix.
transpose()	Transpose this BlockMatrix.
validate()	Validates the block matrix info against the matrix data (blocks) and throws an exception if any error is found.

Attributes

blocks	The RDD of sub-matrix blocks ((blockRowIndex, blockColIndex), sub-matrix) that form this distributed matrix.
colsPerBlock	Number of columns that make up each block.
numColBlocks	Number of columns of blocks in the BlockMatrix.
numRowBlocks	Number of rows of blocks in the BlockMatrix.
rowsPerBlock	Number of rows that make up each block.

Methods Documentation

add(other)

Adds two block matrices together. The matrices must have the same size and matching rowsPerBlock and colsPerBlock values. If one of the sub matrix blocks that are being added is a SparseMatrix, the resulting sub matrix block will also be a SparseMatrix, even if it is being added to a DenseMatrix. If two dense sub matrix blocks are added, the output block will also be a DenseMatrix.

Examples

>>> dm1 = Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])
>>> dm2 = Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12])
>>> sm = Matrices.sparse(3, 2, [0, 1, 3], [0, 1, 2], [7, 11, 12])
>>> blocks1 = sc.parallelize([((0, 0), dm1), ((1, 0), dm2)])
>>> blocks2 = sc.parallelize([((0, 0), dm1), ((1, 0), dm2)])
>>> blocks3 = sc.parallelize([((0, 0), sm), ((1, 0), dm2)])
>>> mat1 = BlockMatrix(blocks1, 3, 2)
>>> mat2 = BlockMatrix(blocks2, 3, 2)
>>> mat3 = BlockMatrix(blocks3, 3, 2)

>>> mat1.add(mat2).toLocalMatrix()
DenseMatrix(6, 2, [2.0, 4.0, 6.0, 14.0, 16.0, 18.0, 8.0, 10.0, 12.0, 20.0, 22.0, 24.0], 0)

>>> mat1.add(mat3).toLocalMatrix()
DenseMatrix(6, 2, [8.0, 2.0, 3.0, 14.0, 16.0, 18.0, 4.0, 16.0, 18.0, 20.0, 22.0, 24.0], 0)

cache()

Caches the underlying RDD.

New in version 2.0.0.

multiply(other)

Left multiplies this BlockMatrix by other, another BlockMatrix. The colsPerBlock of this matrix must equal the rowsPerBlock of other. If other contains any SparseMatrix blocks, they will have to be converted to DenseMatrix blocks. The output BlockMatrix will only consist of DenseMatrix blocks. This may cause some performance issues until support for multiplying two sparse matrices is added.

Examples

>>> dm1 = Matrices.dense(2, 3, [1, 2, 3, 4, 5, 6])
>>> dm2 = Matrices.dense(2, 3, [7, 8, 9, 10, 11, 12])
>>> dm3 = Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])
>>> dm4 = Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12])
>>> sm = Matrices.sparse(3, 2, [0, 1, 3], [0, 1, 2], [7, 11, 12])
>>> blocks1 = sc.parallelize([((0, 0), dm1), ((0, 1), dm2)])
>>> blocks2 = sc.parallelize([((0, 0), dm3), ((1, 0), dm4)])
>>> blocks3 = sc.parallelize([((0, 0), sm), ((1, 0), dm4)])
>>> mat1 = BlockMatrix(blocks1, 2, 3)
>>> mat2 = BlockMatrix(blocks2, 3, 2)
>>> mat3 = BlockMatrix(blocks3, 3, 2)

>>> mat1.multiply(mat2).toLocalMatrix()
DenseMatrix(2, 2, [242.0, 272.0, 350.0, 398.0], 0)

>>> mat1.multiply(mat3).toLocalMatrix()
DenseMatrix(2, 2, [227.0, 258.0, 394.0, 450.0], 0)

numCols()

Get or compute the number of cols.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])

>>> mat = BlockMatrix(blocks, 3, 2)
>>> print(mat.numCols())
2

>>> mat = BlockMatrix(blocks, 3, 2, 7, 6)
>>> print(mat.numCols())
6

numRows()

Get or compute the number of rows.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])

>>> mat = BlockMatrix(blocks, 3, 2)
>>> print(mat.numRows())
6

>>> mat = BlockMatrix(blocks, 3, 2, 7, 6)
>>> print(mat.numRows())
7

persist(storageLevel)

Persists the underlying RDD with the specified storage level.

New in version 2.0.0.

subtract(other)

Subtracts the given block matrix other from this block matrix: this - other. The matrices must have the same size and matching rowsPerBlock and colsPerBlock values. If one of the sub matrix blocks that are being subtracted is a SparseMatrix, the resulting sub matrix block will also be a SparseMatrix, even if it is being subtracted from a DenseMatrix. If two dense sub matrix blocks are subtracted, the output block will also be a DenseMatrix.

New in version 2.0.0.

Examples

>>> dm1 = Matrices.dense(3, 2, [3, 1, 5, 4, 6, 2])
>>> dm2 = Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12])
>>> sm = Matrices.sparse(3, 2, [0, 1, 3], [0, 1, 2], [1, 2, 3])
>>> blocks1 = sc.parallelize([((0, 0), dm1), ((1, 0), dm2)])
>>> blocks2 = sc.parallelize([((0, 0), dm2), ((1, 0), dm1)])
>>> blocks3 = sc.parallelize([((0, 0), sm), ((1, 0), dm2)])
>>> mat1 = BlockMatrix(blocks1, 3, 2)
>>> mat2 = BlockMatrix(blocks2, 3, 2)
>>> mat3 = BlockMatrix(blocks3, 3, 2)

>>> mat1.subtract(mat2).toLocalMatrix()
DenseMatrix(6, 2, [-4.0, -7.0, -4.0, 4.0, 7.0, 4.0, -6.0, -5.0, -10.0, 6.0, 5.0, 10.0], 0)

>>> mat2.subtract(mat3).toLocalMatrix()
DenseMatrix(6, 2, [6.0, 8.0, 9.0, -4.0, -7.0, -4.0, 10.0, 9.0, 9.0, -6.0, -5.0, -10.0], 0)

toCoordinateMatrix()

Convert this matrix to a CoordinateMatrix.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(1, 2, [1, 2])),
...                          ((1, 0), Matrices.dense(1, 2, [7, 8]))])
>>> mat = BlockMatrix(blocks, 1, 2).toCoordinateMatrix()
>>> mat.entries.take(3)
[MatrixEntry(0, 0, 1.0), MatrixEntry(0, 1, 2.0), MatrixEntry(1, 0, 7.0)]

toIndexedRowMatrix()

Convert this matrix to an IndexedRowMatrix.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2).toIndexedRowMatrix()

>>> # This BlockMatrix will have 6 effective rows, due to
>>> # having two sub-matrix blocks stacked, each with 3 rows.
>>> # The ensuing IndexedRowMatrix will also have 6 rows.
>>> print(mat.numRows())
6

>>> # This BlockMatrix will have 2 effective columns, due to
>>> # having two sub-matrix blocks stacked, each with 2 columns.
>>> # The ensuing IndexedRowMatrix will also have 2 columns.
>>> print(mat.numCols())
2

toLocalMatrix()

Collect the distributed matrix on the driver as a DenseMatrix.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2).toLocalMatrix()

>>> # This BlockMatrix will have 6 effective rows, due to
>>> # having two sub-matrix blocks stacked, each with 3 rows.
>>> # The ensuing DenseMatrix will also have 6 rows.
>>> print(mat.numRows)
6

>>> # This BlockMatrix will have 2 effective columns, due to
>>> # having two sub-matrix blocks stacked, each with 2
>>> # columns. The ensuing DenseMatrix will also have 2 columns.
>>> print(mat.numCols)
2

transpose()

Transpose this BlockMatrix. Returns a new BlockMatrix instance sharing the same underlying data. Is a lazy operation.

New in version 2.0.0.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2)

>>> mat_transposed = mat.transpose()
>>> mat_transposed.toLocalMatrix()
DenseMatrix(2, 6, [1.0, 4.0, 2.0, 5.0, 3.0, 6.0, 7.0, 10.0, 8.0, 11.0, 9.0, 12.0], 0)

validate()

Validates the block matrix info against the matrix data (blocks) and throws an exception if any error is found.

New in version 2.0.0.

Attributes Documentation

blocks

The RDD of sub-matrix blocks ((blockRowIndex, blockColIndex), sub-matrix) that form this distributed matrix.

Examples

>>> mat = BlockMatrix(
...     sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                     ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))]), 3, 2)
>>> blocks = mat.blocks
>>> blocks.first()
((0, 0), DenseMatrix(3, 2, [1.0, 2.0, 3.0, 4.0, 5.0, 6.0], 0))

colsPerBlock

Number of columns that make up each block.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2)
>>> mat.colsPerBlock
2

numColBlocks

Number of columns of blocks in the BlockMatrix.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2)
>>> mat.numColBlocks
1

numRowBlocks

Number of rows of blocks in the BlockMatrix.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2)
>>> mat.numRowBlocks
2

rowsPerBlock

Number of rows that make up each block.

Examples

>>> blocks = sc.parallelize([((0, 0), Matrices.dense(3, 2, [1, 2, 3, 4, 5, 6])),
...                          ((1, 0), Matrices.dense(3, 2, [7, 8, 9, 10, 11, 12]))])
>>> mat = BlockMatrix(blocks, 3, 2)
>>> mat.rowsPerBlock
3

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