From 71b6c22c6fc971510b41d3fde19f99ad2e6219e5 Mon Sep 17 00:00:00 2001
From: Sebastian Baunsgaard <baunsgaard@apache.org>
Date: Mon, 3 Feb 2025 15:18:57 +0100
Subject: [PATCH] Identity Matrix exploit

---
 .../compress/colgroup/ColGroupDDC.java        | 26 +++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/apache/sysds/runtime/compress/colgroup/ColGroupDDC.java b/src/main/java/org/apache/sysds/runtime/compress/colgroup/ColGroupDDC.java
index 86ebb4400e4..c1b9c65f229 100644
--- a/src/main/java/org/apache/sysds/runtime/compress/colgroup/ColGroupDDC.java
+++ b/src/main/java/org/apache/sysds/runtime/compress/colgroup/ColGroupDDC.java
@@ -601,6 +601,30 @@ public void leftMMIdentityPreAggregateDense(MatrixBlock that, MatrixBlock ret, i
 
 	@Override
 	public void rightDecompressingMult(MatrixBlock right, MatrixBlock ret, int rl, int ru, int nRows, int crl, int cru) {
+		if(_dict instanceof IdentityDictionary)
+			identityRightDecompressingMult(right, ret, rl, ru, crl, cru);
+		else
+			defaultRightDecompressingMult(right, ret, rl, ru, crl, cru);
+	}
+
+	private void identityRightDecompressingMult(MatrixBlock right, MatrixBlock ret, int rl, int ru, int crl, int cru) {
+		final double[] b = right.getDenseBlockValues();
+		final double[] c = ret.getDenseBlockValues();
+		final int jd = right.getNumColumns();
+		final int vLen = 8;
+		final int lenJ = cru - crl;
+		final int end = cru - (lenJ % vLen);
+		for(int i = rl; i < ru; i++) {
+			int k = _data.getIndex(i);
+			final int offOut = i * jd + crl;
+			final double aa = 1;
+			final int k_right = _colIndexes.get(k);
+			vectMM(aa, b, c, end, jd, crl, cru, offOut, k_right, vLen);
+
+		}
+	}
+
+	private void defaultRightDecompressingMult(MatrixBlock right, MatrixBlock ret, int rl, int ru, int crl, int cru) {
 		final double[] a = _dict.getValues();
 		final double[] b = right.getDenseBlockValues();
 		final double[] c = ret.getDenseBlockValues();
@@ -930,8 +954,6 @@ protected void denseSelection(MatrixBlock selection, P[] points, MatrixBlock ret
 		}
 	}
 
-
-
 	private void leftMMIdentityPreAggregateDenseSingleRow(double[] values, int pos, double[] values2, int pos2, int cl,
 		int cu) {
 		IdentityDictionary a = (IdentityDictionary) _dict;