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bug#41223: 28.0.50; Calc gives wrong determinant for some matrices with
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From: |
Mattias Engdegård |
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Subject: |
bug#41223: 28.0.50; Calc gives wrong determinant for some matrices with symbolic variables |
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Date: |
Wed, 13 May 2020 14:58:33 +0200 |
Thank you for reporting this. If Calc cannot compute something, at least it
shouldn't lie.
In this case I'm tempted to apply the expedient below. Would that suffice for
you?
--- a/lisp/calc/calc-mtx.el
+++ b/lisp/calc/calc-mtx.el
@@ -275,7 +275,7 @@ math-do-matrix-lud
k (1+ k)))
(setcar (nthcdr j (nth i lu)) sum)
(let ((dum (math-lud-pivot-check sum)))
- (if (Math-lessp big dum)
+ (if (or (math-zerop big) (Math-lessp big dum))
(setq big dum
imax i)))
(setq i (1+ i)))