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From: chiwanpark <git@git.apache.org>
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Subject: [GitHub] flink pull request #2152: [FLINK-3920] Distributed Linear Algebra: block-bas...
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Message-Id: <20160829040552.6D500E00DB@git1-us-west.apache.org>
Date: Mon, 29 Aug 2016 04:05:52 +0000 (UTC)
archived-at: Mon, 29 Aug 2016 04:05:57 -0000

Github user chiwanpark commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2152#discussion_r76551085
  
    --- Diff: flink-libraries/flink-ml/src/main/scala/org/apache/flink/ml/math/distributed/BlockMapper.scala ---
    @@ -0,0 +1,107 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.flink.ml.math.distributed
    +
    +import org.apache.flink.ml.math.distributed.DistributedMatrix.{MatrixColIndex, MatrixRowIndex}
    +
    +/**
    +  * This class is in charge of handling all the spatial logic required by BlockMatrix.
    +  * It introduces a new space of zero-indexed coordinates (i,j), called "mapped coordinates".
    +  * This is a space where blocks are indexed (starting from zero).
    +  *
    +  * So every coordinate in the original space can be mapped to this space and to the
    +  * corrisponding block.  A block have a row and a column coordinate that explicits
    +  * its position. Every set of coordinates in the mapped space corresponds to a square
    +  * of size rowPerBlock x colsPerBlock.
    +  *
    +  */
    +case class BlockMapper( //original matrix size
    +                       numRows: Int,
    +                       numCols: Int,
    +                       //block size
    +                       rowsPerBlock: Int,
    +                       colsPerBlock: Int) {
    +
    +  require(numRows >= rowsPerBlock && numCols >= colsPerBlock)
    +  val numBlockRows: Int = math.ceil(numRows * 1.0 / rowsPerBlock).toInt
    +  val numBlockCols: Int = math.ceil(numCols * 1.0 / colsPerBlock).toInt
    +  val numBlocks = numBlockCols * numBlockRows
    +
    +  /**
    +    * Translates absolute coordinates to the mapped coordinates of the block
    +    * these coordinates belong to.
    +    * @param i
    +    * @param j
    +    * @return
    +    */
    +  def absCoordToMappedCoord(i: MatrixRowIndex, j: MatrixColIndex): (Int, Int) =
    +    getBlockMappedCoordinates(getBlockIdByCoordinates(i, j))
    +
    +  /**
    +    * Retrieves a block id from original coordinates
    +    * @param i Original row
    +    * @param j Original column
    +    * @return Block ID
    +    */
    +  def getBlockIdByCoordinates(i: MatrixRowIndex, j: MatrixColIndex): Int = {
    +
    +    if (i < 0 || j < 0 || i >= numRows || j >= numCols) {
    +      throw new IllegalArgumentException(s"Invalid coordinates ($i,$j).")
    +    } else {
    +      val mappedRow = i / rowsPerBlock
    +      val mappedColumn = j / colsPerBlock
    +      val res = mappedRow * numBlockCols + mappedColumn
    +
    +      assert(res <= numBlocks)
    +      res
    +    }
    +  }
    +
    +  /**
    +    * Retrieves mapped coordinates for a given block.
    +    * @param blockId
    +    * @return
    +    */
    +  def getBlockMappedCoordinates(blockId: Int): (Int, Int) = {
    +    if (blockId < 0 || blockId > numBlockCols * numBlockRows) {
    +      throw new IllegalArgumentException(
    +          s"BlockId numeration starts from 0. $blockId is not a valid Id"
    +      )
    +    } else {
    +      val i = blockId / numBlockCols
    +      val j = blockId % numBlockCols
    +      (i, j)
    +    }
    +  }
    +
    +  /**
    +    * Retrieves the ID of the block at the given coordinates
    +    * @param i
    +    * @param j
    +    * @return
    +    */
    +  def getBlockIdByMappedCoord(i: Int, j: Int): Int = {
    +
    +    if (i < 0 || j < 0 || i >= numBlockRows || j >= numBlockCols) {
    +      throw new IllegalArgumentException(s"Invalid coordinates ($i,$j).")
    --- End diff --
    
    Please use `require`.


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