com.johnsnowlabs.ml.crf.SparseArray.scala Maven / Gradle / Ivy
/*
* Copyright 2017-2022 John Snow Labs
*
* Licensed 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 com.johnsnowlabs.ml.crf
class SparseArray(val values: Array[(Int, Float)]) {
var prev = -1
for ((idx, _) <- values) {
require(idx > prev, s"index must be sorted $prev must be lower $idx")
prev = idx
}
def apply(idx: Int): Float = binSearch(idx)
private def binSearch(idx: Int, l: Int = 0, r: Int = values.length - 1): Float = {
val mid = (l + r) / 2
if (l > r)
0f
else if (idx == values(mid)._1)
values(mid)._2
else if (idx < values(mid)._1)
binSearch(idx, l, mid - 1)
else
binSearch(idx, mid + 1, r)
}
}
object SparseArray {
implicit class SeqWrapper(values: Seq[(Int, Float)]) {
def toSparse(): SparseArray = {
new SparseArray(values.sortBy(_._1).toArray)
}
}
}