[SYSTEMDS-3540] Check columns for One-Hot-Encoding before compression

conf/log4j-compression.properties

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+#-------------------------------------------------------------
+#
+# 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.
+#
+#-------------------------------------------------------------
+
+log4j.rootLogger=ERROR, console
+
+log4j.logger.org.apache.sysds=INFO
+log4j.logger.org.apache.sysds.runtime.compress=DEBUG
+log4j.logger.org.apache.spark=ERROR
+log4j.logger.org.apache.spark.SparkContext=OFF
+log4j.logger.org.apache.hadoop=ERROR
+
+log4j.appender.console=org.apache.log4j.ConsoleAppender
+log4j.appender.console.target=System.err
+log4j.appender.console.layout=org.apache.log4j.PatternLayout
+log4j.appender.console.layout.ConversionPattern=%d{yy/MM/dd HH:mm:ss} %p %c{2}: %m%n

scripts/perftest/ohe_checks/README.md

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+<!--
+{% comment %}
+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.
+{% end comment %}
+-->
+
+# Checking One Hot Encodedness before Compression tests
+
+To run all tests for One Hot Encoding Checks:
+ * install systemds,
+ * make sure that the paths for SYSTEMDS_ROOT, JAVA_HOME, HADOOP_HOME, LOG4JPROP are correctly set
+ * run experiments.sh
+
+Alternatively, to run the experiment.dml script directly with OHE checks enabled, use this command: 
+
+`$SYSTEMDS_ROOT/bin/systemds $SYSTEMDS_ROOT/target/SystemDS.jar experiment.dml --config ohe.xml `
+
+Note: You can use -nvargs to set the variables rows, cols, dummy, distinct, repeats (how many times you want to generate a random matrix, transform-encode it and compress it)
+
+(Dummy is the array of column indexes that you would like to One Hot Encode, example: dummy="[1]" will One Hot Encode the first column)
+
+To collect the metrics from the logs for easier comparison, you can run `parse_logs.py` and an excel file called `combined_metrics.xlsx` will be created in this directory.
+---
+# Documentation of Changes to codebase for Implementing OHE Checks
+
+## Flag to enable/disable OHE checks (Disabled by default)
+- Added ``COMPRESSED_ONEHOTDETECT = "sysds.compressed.onehotdetect"`` to ``DMLConfig`` and adjusted the relevant methods
+- Added attribute to ``CompressionSettings`` ``public final boolean oneHotDetect`` and adjusted the methods
+- Adjusted ``CompressionSettingsBuilder`` to check if ``COMPRESSED_ONEHOTDETECT`` has been set to true to enable the checks 
+
+## Changes in  `CoCoderFactory` 
+
+### 1. Introduction of OHE Detection
+
+**Condition Addition:**
+- Added a condition to check for `cs.oneHotDetect` along with the existing condition `!containsEmptyConstOrIncompressable` in the `findCoCodesByPartitioning` method. This ensures that the process considers OHE detection only if it is enabled in the compression settings.
+- Original code only checked for `containsEmptyConstOrIncompressable` and proceeded to cocode all columns if false. The updated code includes an additional check for `cs.oneHotDetect`.
+
+### 2. New Data Structures for OHE Handling
+
+**New Lists:** Introduced two new lists to manage the OHE detection process:
+- `currentCandidates`: To store the current candidate columns that might form an OHE group.
+- `oheGroups`: To store lists of columns that have been validated as OHE groups.
+
+### 3. Filtering Logic Enhancements
+
+**Column Filtering:** Enhanced the loop that iterates over columns to identify OHE candidates:
+- Columns that are empty, constant, or incompressible are filtered into respective lists.
+- For other columns, they are added to `currentCandidates` if they are deemed candidates (via `isCandidate` function).
+
+### 4. Addition of `isHotEncoded` Function
+
+**Function Creation:** Created a new `isHotEncoded` function to evaluate if the accumulated columns form a valid OHE group.
+- **Parameters:** Takes a list of column groups (`colGroups`), a boolean flag (`isSample`), an array of non-zero counts (`nnzCols`), and the number of rows (`numRows`).
+- **Return Type:** Returns a `String` indicating the status of the current candidates:
+  - `"POTENTIAL_OHE"`: When the current candidates could still form an OHE group.
+  - `"NOT_OHE"`: When the current candidates cannot form an OHE group.
+  - `"VALID_OHE"`: When the current candidates form a valid OHE group.
+- **Logic:** The function calculates the total number of distinct values and offsets, and checks if they meet the criteria for forming an OHE group.
+
+### 5. Enhanced Group Handling
+
+**Candidate Processing:** Within the loop, after adding a column to `currentCandidates`:
+- Calls `isHotEncoded` to check the status of the candidates.
+- If `isHotEncoded` returns `"NOT_OHE"`, moves the candidates to regular groups and clears the candidates list.
+- If `isHotEncoded` returns `"VALID_OHE"`, moves the candidates to `oheGroups` and clears the candidates list.
+- If `isHotEncoded` returns `"POTENTIAL_OHE"`, continues accumulating candidates.
+
+### 6. Final Candidate Check
+
+**Post-loop Check:** After the loop, checks any remaining `currentCandidates`:
+- If they form a valid OHE group, adds them to `oheGroups`.
+- Otherwise, adds them to regular groups.
+
+### 7. Overwrite and CoCode Groups
+
+**Overwrite Groups:** Updates `colInfos.compressionInfo` with the processed `groups`.
+**OHE Group Integration:** Combines indexes for validated OHE groups and adds them to the final `groups`.
+
+## One Hot Encoded Columns Compression in `ColGroupFactory`
+
+### Description
+
+The `compressOHE` function is designed to compress columns that are one-hot encoded (OHE). It validates and processes the input data to ensure it meets the criteria for one-hot encoding, and if so, it compresses the data accordingly. If the data does not meet the OHE criteria, it falls back to a direct compression method (`directCompressDDC`).
+
+### Implementation Details
+
+1. **Validation of `numVals`**:
+   - Ensures the number of distinct values (`numVals`) in the column group is greater than 0.
+   - Throws a `DMLCompressionException` if `numVals` is less than or equal to 0.
+
+2. **Handling Transposed Matrix**:
+   - If the matrix is transposed (`cs.transposed` is `true`):
+     - Creates a `MapToFactory` data structure with an additional unique value.
+     - Iterates through the sparse block of the matrix, checking for non-one values or multiple ones in the same row.
+     - If a column index in the sparse block is empty, or if non-one values or multiple ones are found, it falls back to `directCompressDDC`.
+
+3. **Handling Non-Transposed Matrix**:
+   - If the matrix is not transposed (`cs.transposed` is `false`):
+     - Creates a `MapToFactory` data structure.
+     - Iterates through each row of the matrix:
+       - Checks for the presence of exactly one '1' in the columns specified by `colIndexes`.
+       - If multiple ones are found in the same row, or if no '1' is found in a sample row, it falls back to `directCompressDDC`.
+
+4. **Return Value**:
+   - If the data meets the OHE criteria, returns a `ColGroupDDC` created with the column indexes, an `IdentityDictionary`, and the data.
+   - If the data does not meet the OHE criteria, returns the result of `directCompressDDC`.
+
+## Add method in `ColGroupSizes`
+Added method ``estimateInMemorySizeOHE(int nrColumns, boolean contiguousColumns, int nrRows)``
+
+## Add method in `AComEst`
+Added a getter method `getNnzCols`
+
+## Edit `distinctCountScale` method in `ComEstSample`
+```java 
+if(freq == null || freq.length == 0)
+    return numOffs+1;
+```
+And added condition:
+```java
+if(sampleFacts.numRows>sampleFacts.numOffs)
+    est += 1;
+```
+<span style="color:red">Warning: This Change will cause some tests to fail</span>.
+
+
+## Edit constructor in `CompressedSizeInfoColGroup`
+Added a case in switch statement for OHE
+
+## Added attribute in `CompressionStatistics`
+Added Sparsity of input matrix attribute ``public double sparsity;`` to add logging in ``CompressedMatrixBlockFactory``
+## Fix Bug in `extractFacts` method in `SparseEncoding`
+Number of distinct values returned was wrong. 
+Fix: In the return statements, changed map.getUnique() to getUnique()
+
+## Fix Bug in `outputMatrixPostProcessing` method in `MultiColumnEncoder`
+Instead of just recomputing nonzeroes in the else block, added `output.examSparsity(k);`

scripts/perftest/ohe_checks/experiment.dml

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+#-------------------------------------------------------------
+#
+# 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.
+#
+#-------------------------------------------------------------
+
+## This script generates a random matrix, transforms some columns to be One-Hot-Encoded, and then compresses
+
+# Set default values
+default_rows = 1000
+default_cols = 10
+default_dummy = "[1]"
+default_repeats = 1
+default_num_distinct = 10
+
+#nvargs
+rows = ifdef($rows, default_rows)
+cols = ifdef($cols, default_cols)
+dummy = ifdef($dummy, default_dummy)
+repeats = ifdef($repeats, default_repeats)
+num_distinct = ifdef($distinct, default_num_distinct)
+
+# Generate random matrix and apply transformations
+x = rand(rows=rows, cols=cols, min=0, max=num_distinct)
+x = floor(x)
+Fall = as.frame(x)
+jspec = "{ids: true, dummycode: " + dummy + "}";
+for(i in 1:repeats){
+	[T,M] = transformencode(target=Fall, spec=jspec)
+	xc = compress(T)
+}
+print(toString(xc))

scripts/perftest/ohe_checks/experiments.sh

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+#!/usr/bin/env bash
+#-------------------------------------------------------------
+#
+# 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.
+#
+#-------------------------------------------------------------
+
+mkdir BaselineLogs
+mkdir OHELogs
+run_base() {
+    $SYSTEMDS_ROOT/bin/systemds $SYSTEMDS_ROOT/target/SystemDS.jar experiment.dml \
+    --seed 42 --debug -nvargs rows=$1 cols=$2 dummy="$3" distinct=$4 > BaselineLogs/${5}_${1}_rows_${2}_cols_${3}_encoded_base.txt 2>&1
+}
+
+run_ohe() {
+    $SYSTEMDS_ROOT/bin/systemds $SYSTEMDS_ROOT/target/SystemDS.jar experiment.dml \
+    --seed 42 --debug --config ohe.xml -nvargs rows=$1 cols=$2 dummy="$3" distinct=$4> OHELogs/${5}_${1}_rows_${2}_cols_${3}_encoded_ohe.txt 2>&1
+}
+
+# Run same experiments but checking One-Hot-Encoded columns first
+run_ohe 1000 1 "[1]" 10 1
+run_ohe 1000 5 "[2]" 10 2
+run_ohe 1000 5 "[1,2]" 10 3
+run_ohe 1000 5 "[1,2,3]" 10 4
+run_ohe 1000 5 "[1,2,3,4,5]" 10 5
+run_ohe 1000 10 "[1,3,5]" 10 6
+run_ohe 1000 10 "[1,2,5,6]" 10 7
+run_ohe 100000 1 "[1]" 100 8
+run_ohe 100000 5 "[1,2]" 100 9
+run_ohe 100000 5 "[1,2,3]" 100 10
+run_ohe 100000 100 "[1,3,50,60,70,80]" 100 11
+run_ohe 100000 100 "[1,2,24,25,50,51]" 100 12
+
+# Run baseline experiments
+run_base 1000 1 "[1]" 10 1
+run_base 1000 5 "[2]" 10 2
+run_base 1000 5 "[1,2]" 10 3
+run_base 1000 5 "[1,2,3]" 10 4
+run_base 1000 5 "[1,2,3,4,5]" 10 5
+run_base 1000 10 "[1,3,5]" 10 6
+run_base 1000 10 "[1,2,5,6]" 10 7
+run_base 100000 1 "[1]" 100 8
+run_base 100000 5 "[1,2]" 100 9
+run_base 100000 5 "[1,2,3]" 100 10
+run_base 100000 100 "[1,3,50,60,70,80]" 100 11
+run_base 100000 100 "[1,2,24,25,50,51]" 100 12

scripts/perftest/ohe_checks/ohe.xml

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+<!--
+ * 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.
+-->
+
+<root>
+ <sysds.compressed.onehotdetect>true</sysds.compressed.onehotdetect>   
+</root>