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Update determinant with better recommendations, and follow them. #4843

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Update determinant with better recommendations, and follow them.
HansOlsson Oct 26, 2026
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FixSyntax
HansOlsson Oct 26, 2026
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2 changes: 1 addition & 1 deletion Modelica/Electrical/Polyphase/Basic/MutualInductor.mo
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Expand Up @@ -4,7 +4,7 @@ model MutualInductor "Linear mutual inductor"
parameter Real epsilon=1e-9 "Relative accuracy tolerance of matrix symmetry";
parameter SI.Inductance L[m, m] "Mutual inductance matrix";
initial equation
if abs(Modelica.Math.Matrices.det(L)) < epsilon then
if Modelica.Math.Matrices.rcond(L) < epsilon then
Modelica.Utilities.Streams.print("Warning: mutual inductance matrix singular!");
end if;
equation
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2 changes: 1 addition & 1 deletion Modelica/Electrical/QuasiStatic/Polyphase/Basic/MutualInductor.mo
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Expand Up @@ -5,7 +5,7 @@ model MutualInductor "Linear mutual inductor"
parameter Real epsilon=1e-9 "Relative accuracy tolerance of matrix symmetry";
parameter SI.Inductance L[m, m] "Mutual inductance matrix";
initial equation
if abs(Modelica.Math.Matrices.det(L)) < epsilon then
if Modelica.Math.Matrices.rcond(L) < epsilon then
Modelica.Utilities.Streams.print("Warning: mutual inductance matrix singular!");
end if;
equation
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13 changes: 6 additions & 7 deletions Modelica/Math/package.mo
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Expand Up @@ -2579,18 +2579,17 @@ result = Matrices.<strong>det</strong>(A);
This function returns the determinant \"result\" of matrix A
computed by a LU decomposition with row pivoting. For details about determinants, see
<a href=\"http://en.wikipedia.org/wiki/Determinant\">http://en.wikipedia.org/wiki/Determinant</a>.
Usually, this function should never be used, because
Usually, this function should not be used, because
there are nearly always better numerical algorithms
as by computing the determinant. Examples:
than computing the determinant. Examples:
</p>

<ul>
<li> Use <a href=\"modelica://Modelica.Math.Matrices.rank\">Matrices.rank</a>
to compute whether det(A) = 0 (i.e., Matrices.rank(A) &lt; size(A,1)).</li>

<li> Use <a href=\"modelica://Modelica.Math.Matrices.solve\">Matrices.solve</a>
to solve the linear equation A*x = b, instead of using determinants to
compute the solution.</li>
to solve the linear equation A*x = b.</li>

<li> Use <a href=\"modelica://Modelica.Math.Matrices.rcond\">Matrices.rcond</a>(A)>=epsilon
to check that the system is well-conditioned and not singular.</li>
</ul>

<h4>See also</h4>
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