From: Pasukhin Dmitry <dpasukhi@opencascade.com>
Date: Tue, 24 Jun 2025 11:38:31 +0000 (+0100)
Subject: Foundation Classes - Matrix multiplied issue (#522)
X-Git-Tag: V7_9_2~23
X-Git-Url: http://git.dev.opencascade.org/gitweb/?a=commitdiff_plain;h=9cf1fb1d7c44ab856ba9d33e9d7d4915f81d542f;p=occt.git

Foundation Classes - Matrix multiplied issue (#522)

Refactor multiplication to avoid self-correlation issues by using a temporary copy.
---

diff --git a/src/math/math_Matrix.cxx b/src/math/math_Matrix.cxx
index b2a61e1667..b7fa5177ab 100644
--- a/src/math/math_Matrix.cxx
+++ b/src/math/math_Matrix.cxx
@@ -635,6 +635,14 @@ void math_Matrix::Multiply(const math_Matrix& Right)
     ColNumber() != Right.RowNumber(),
     "math_Matrix::Multiply() - input matrix has incompatible dimensions");
 
+  // Create a temporary copy to avoid corrupting our own data during calculation
+  math_Matrix aTemp = *this;
+  if (this == &Right)
+  {
+    Multiply(aTemp, aTemp);
+    return;
+  }
+
   Standard_Real Som;
   for (Standard_Integer I = LowerRowIndex; I <= UpperRowIndex; I++)
   {
@@ -644,7 +652,7 @@ void math_Matrix::Multiply(const math_Matrix& Right)
       Standard_Integer I2 = Right.LowerRowIndex;
       for (Standard_Integer J = LowerColIndex; J <= UpperColIndex; J++)
       {
-        Som = Som + Array(I, J) * Right.Array(I2, J2);
+        Som += aTemp.Array(I, J) * Right.Array(I2, J2);
         I2++;
       }
       Array(I, J2) = Som;