Difference between revisions of "Slices"

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This assignment has been replaced by [[Ranges]].
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credit for this assignment: Finn Voichick and Dennis Cosgrove
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=Motivation=
 
=Motivation=
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Coarsening, or n-way split as we tend to call it in this course, comes up a fair amount.  This studio has you implement a utility that you can use over and over throughout the semester.
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Coarsening, or n-way split as we tend to call it in this course, comes up a fair amount.  In this studio, we will create our Slices class, that allows us to split up our data n-times (depending on what value we pass in) in a consistent organized fashion. This makes sure that each thread is balanced in the work that it does, minimizing the Critical Path Length.
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Since we will be utilizing this class throughout the semester in different studios and assignments, it is important that data is split up in a specific way. The tests should help make sure your solution is in working order.
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=Mistakes To Avoid=
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{{warning | Do NOT Parallelize}}
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This studio is about creating an easier way to split data so that it can be worked on in parallel. The splitting of the data is still done sequentially. That means at no point in this studio should you be using async() or finish().
  
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In order to support future testing well, we are strict about exactly how the data is split up among the slices.
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=Code To Investigate=
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[https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/IndexedRange.html class IndexedRange]
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:[https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/IndexedRange.html#%3Cinit%3E(int,int,int) constructor].
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<pre>public IndexedRange(int sliceIndexId, int minInclusive, int maxExclusive)</pre>
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This class has everything you need for [[Nucleobase_Counting#Coarsening_N-Way_Split|n-way split]] problems, specifically: [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/IndexedRange.html#getSliceIndexId() getSliceIndexId()], [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/IndexedRange.html#getMinInclusive() getMinInclusive()], and [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/IndexedRange.html#getMaxExclusive() getMaxExclusive()].
  
 
=Code to Implement=
 
=Code to Implement=
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{{CodeToImplement|Slices|createNSlicesForArrayObject|slices.studio}}
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{{CodeToImplement|Slices|createNSlices|slices.studio}}
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==createNSlices==
  
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==createNSlicesForArrayObject==
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{{Sequential|public static List<IndexedRange> createNSlices(int minInclusive, int maxExclusive, int numSlices)}}
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In order to support primitive arrays (e.g. byte[], int[], et cetera) and non-primitive arrays (e.g. Object[]) we provide all of the public methods, each which simply call the single method requiring implementation:
 
  
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{{Sequential|createNSlicesForArrayObject}}
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Given a range [minInclusive, maxExclusive) and a number of slices to make, return a List of IndexedRanges. Understanding what a IndexedRange is and how it is used is important when writing this solution.
  
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<nowiki> public static <T> List<Slice<T[]>> createNSlices(T[] data, int numSlices) {
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The goal is to have each slice's range be the entire array when put together, with no overlap. Some examples are giving below. Working through more examples can be a helpful way of figuring out what code to write if you get stuck.
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<byte[]>> createNSlices(byte[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<char[]>> createNSlices(char[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<short[]>> createNSlices(short[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<int[]>> createNSlices(int[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<long[]>> createNSlices(long[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<float[]>> createNSlices(float[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}
 
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public static List<Slice<double[]>> createNSlices(double[] data, int numSlices) {
 
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return createNSlicesForArrayObject(data, numSlices);
 
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}</nowiki>
 
  
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To pull this off we will need to use the [https://docs.oracle.com/javase/8/docs/api/java/lang/reflect/Array.html#getLength-java.lang.Object- Array.getLength(Object)] method.
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{{ tip | In a slice, the minimum is inclusive and the maximum is exclusive. This means for two slices next to each other, slice1.getMaxExclusive() is equal to slice2.getMinInclusive(). }}
  
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=Strict Specification=
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==Strict Specification==
 
We are overly strict about the specification of how the data '''must''' be sliced up.  This is to allow to accurately compare results intermediate results throughout the semester.
 
We are overly strict about the specification of how the data '''must''' be sliced up.  This is to allow to accurately compare results intermediate results throughout the semester.
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==Example: array.length=7; numSlices=4==
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Distribute the remainder 1 each to the lower end slices.
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'''Example: array.length=8; numSlices=4'''
  
 
{| class="wikitable"
 
{| class="wikitable"
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|C
 
|C
 
|C
 
|C
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|D
 
|D
 
|D
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|}
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{| class="wikitable"
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|-
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!Slice ID !! Min Inclusive !! Max Exclusive
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|-
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|0 || 0 || 2
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|-
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|1 || 2 || 4
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|-
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|2 || 4 || 6
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|-
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|3 || 6 || 8
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|}
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'''Example: array.length=7; numSlices=4'''
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Distribute the remainder 1 each to the lower end slices (the first few slices or the lower index slices).
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{| class="wikitable"
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|A
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|A
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|B
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|B
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|C
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|C
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|D
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|}
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{| class="wikitable"
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|-
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!Slice ID !! Min Inclusive !! Max Exclusive
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|-
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|0 || 0 || 2
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|-
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|1 || 2 || 4
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|-
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|2 || 4 || 6
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|-
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|3 || 6 || 7
 
|}
 
|}
  
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</s>
 
</s>
  
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=Mistakes To Avoid=
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Giving all the remainder to one slice defeats the purpose of balancing the workload!
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{{warning | Do NOT Parallelize}}
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==Convenience Methods==
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 +
In order to support primitive arrays (e.g. byte[], int[], et cetera) and non-primitive arrays (e.g. Object[]) we provide all of the public methods, each which simply call the single method requiring implementation:
 +
 
 +
<nowiki> public static <C> List<IndexedRange> createNSlices(C[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}
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public static List<IndexedRange> createNSlices(byte[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}
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public static List<IndexedRange> createNSlices(char[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}
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public static List<IndexedRange> createNSlices(short[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}
  
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{{warning | Do NOT Copy The Data Into SubArrays}}
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public static List<IndexedRange> createNSlices(int[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}
  
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=class Slice<T>=
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public static List<IndexedRange> createNSlices(long[] data, int numSlices) {
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use: [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/Slice.html class Slice]
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return createNSlices(0, data.length, numSlices);
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}
  
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This class has everything you need for [[Nucleobase_Counting#Coarsening_N-Way_Split|n-way split]] problems, specifically: [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/Slice.html#getSliceIndexId-- getSliceIndexId()], [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/Slice.html#getMinInclusive-- getMinInclusive()], and [https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/Slice.html#getMaxExclusive-- getMaxExclusive()].
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public static List<IndexedRange> createNSlices(float[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}
  
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[https://www.cse.wustl.edu/~cosgroved/courses/cse231/current/apidocs/slice/core/Slice.html#getOriginalUnslicedData-- getOriginalUnslicedData()] is not necessary until the [[K-MerCounting_Assignment|K-Mer Counting Lab]]
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public static List<IndexedRange> createNSlices(double[] data, int numSlices) {
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return createNSlices(0, data.length, numSlices);
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}</nowiki>
  
 
=Testing Your Solution=
 
=Testing Your Solution=
 
==Correctness==
 
==Correctness==
 
{{TestSuite|SlicesTestSuite|slice.studio}}
 
{{TestSuite|SlicesTestSuite|slice.studio}}
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=Pledge, Acknowledgments, Citations=
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{{Pledge|studio-slices}}
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Latest revision as of 21:56, 30 November 2022

This assignment has been replaced by Ranges.

Retrieved from "http://classes.engineering.wustl.edu/cse231/core/index.php?title=Slices&oldid=4155"