* bug#35374: Calc; Div by 0 in solving system
@ 2019-04-22 5:20 Christopher Howard
2019-09-22 17:34 ` Mattias Engdegård
0 siblings, 1 reply; 5+ messages in thread
From: Christopher Howard @ 2019-04-22 5:20 UTC (permalink / raw)
To: 35374
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Place this on stack with algebriac mode:
[2 * x - 3 * y + z = 5, x + y - 2 * z = 0, -x + 2 * y + 3 * z = -3]
run command 'a S x,y,z'
Receive error 'Division by zero: 1'
I enabled Debug on Error but could not find the backtrace
Emacs : GNU Emacs 25.1.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
of 2017-09-14, modified by Debian
Package: Calc
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^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#35374: Calc; Div by 0 in solving system
[not found] <1555861067.5469.3.camel@qlfiles.net>
@ 2019-04-23 14:34 ` Mattias Engdegård
0 siblings, 0 replies; 5+ messages in thread
From: Mattias Engdegård @ 2019-04-23 14:34 UTC (permalink / raw)
To: Christopher Howard; +Cc: 35374
21 apr. 2019 kl. 17.37 skrev Christopher Howard <christopher.howard@qlfiles.net>:
> I enabled Debug on Error but could not find the backtrace
Reproduced in 26.1. Backtrace below.
I quickly got lost in calcalg2.el, but it looks like the equation
2(z - 1.0) - (5 + 3(z - 1.0) - z) / 2 + 3z + 3 = 0,
isn't solved properly by math-try-solve-for: math-decompose-poly returns the correct decomposition of the LHS, (4) * z, but then the code decides to find a root of the polynomial (4) which of course doesn't exist and nothing good comes out of it. I'm not sure why the floating-point numbers (float 1 0) are there in the first place.
Maybe someone more knowledgeable about Calc can help further.
* math-reject-arg((float 1 0) "*Division by zero")
math-div-by-zero((float 1 0) 0)
math-div((float 1 0) 0)
math-float((frac 1 0))
math-mul((frac 1 0) (float 138629436111989 -14))
math-mul-objects-fancy((frac 1 0) (cplx (float 138629436111989 -14) (float 314159265358979 -14)))
math-mul((frac 1 0) (cplx (float 138629436111989 -14) (float 314159265358979 -14)))
math-pow-fancy(-4 (frac 1 0))
math-pow(-4 (frac 1 0))
math-poly-laguerre-root((4) 0 t)
math-poly-any-root((4) 0 t)
math-try-solve-for((+ (+ (- (* 2 (- (var z var-z) (float 1 0))) (/ (- (+ 5 (* 3 (- (var z var-z) (float 1 0)))) (var z var-z)) 2)) (* 3 (var z var-z))) 3) 0 nil nil)
math-try-solve-for((calcFunc-eq (+ (- (* 2 (- (var z var-z) (float 1 0))) (/ (- (+ 5 (* 3 (- (var z var-z) (float 1 0)))) (var z var-z)) 2)) (* 3 (var z var-z))) -3) 0 nil)
math-solve-for((calcFunc-eq (+ (- (* 2 (- (var z var-z) (float 1 0))) (/ (- (+ 5 (* 3 (- (var z var-z) (float 1 0)))) (var z var-z)) 2)) (* 3 (var z var-z))) -3) 0 (var z var-z) nil)
math-solve-system-rec((((calcFunc-eq (+ (- (* 2 (- (var z var-z) (float 1 0))) (/ (- (+ 5 (* 3 (- (var z var-z) (float 1 0)))) (var z var-z)) 2)) (* 3 (var z var-z))) -3))) ((var z var-z)) (((var y var-y) (- (var z var-z) (float 1 0))) ((var x var-x) (/ (- (+ 5 (* 3 (- (var z var-z) (float 1 0)))) (var z var-z)) 2))))
math-solve-system-rec((((calcFunc-eq (- (+ (/ (- (+ 5 (* 3 (var y var-y))) (var z var-z)) 2) (var y var-y)) (* 2 (var z var-z))) 0)) ((calcFunc-eq (+ (- (* 2 (var y var-y)) (/ (- (+ 5 (* 3 (var y var-y))) (var z var-z)) 2)) (* 3 (var z var-z))) -3))) ((var y var-y) (var z var-z)) (((var x var-x) (/ (- (+ 5 (* 3 (var y var-y))) (var z var-z)) 2))))
math-solve-system-rec((((calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5)) ((calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0)) ((calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3))) ((var x var-x) (var y var-y) (var z var-z)) nil)
math-solve-system((vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z)) nil)
calcFunc-solve((vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z)))
apply(calcFunc-solve ((vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
math-normalize((calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
math-simplify((calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
calc-normalize-fancy((calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
calc-normalize((calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
math-evaluate-expr((calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z))))
mapcar(math-evaluate-expr ((calcFunc-solve (vec (calcFunc-eq (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z)) 5) (calcFunc-eq (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z))) 0) (calcFunc-eq (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z))) -3)) (vec (var x var-x) (var y var-y) (var z var-z)))))
#f(compiled-function () #<bytecode 0x4a71afd9>)()
calc-do(#f(compiled-function () #<bytecode 0x4a71afd9>) 126)
calc-evaluate(1)
funcall-interactively(calc-evaluate 1)
call-interactively(calc-evaluate nil nil)
command-execute(calc-evaluate)
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#35374: Calc; Div by 0 in solving system
2019-04-22 5:20 Christopher Howard
@ 2019-09-22 17:34 ` Mattias Engdegård
2019-09-23 5:28 ` Christopher Howard
0 siblings, 1 reply; 5+ messages in thread
From: Mattias Engdegård @ 2019-09-22 17:34 UTC (permalink / raw)
To: 35374; +Cc: Christopher Howard
[-- Attachment #1: Type: text/plain, Size: 343 bytes --]
tags 35374 patch
stop
> Maybe someone more knowledgeable about Calc can help further.
Much to our surprise, very few people volunteered their service. Now, despite being grossly under-qualified for the task, I did give it a go. After all, we can't have it fail on simple linear equation systems now can we.
Please try this patch.
[-- Attachment #2: 0001-Fix-linear-equation-system-solving-in-Calc-bug-35374.patch --]
[-- Type: application/octet-stream, Size: 6111 bytes --]
From 980a1f0b73d2aa58335a47ad4a68005a28307a4b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mattias=20Engdeg=C3=A5rd?= <mattiase@acm.org>
Date: Sun, 22 Sep 2019 15:03:02 +0200
Subject: [PATCH] Fix linear equation system solving in Calc (bug#35374)
* lisp/calc/calcalg2.el (math-try-solve-for):
To solve Ax^n=0 where A is a nonzero constant and x the variable to
solve for, solve x^n=0 instead of solving A=0 (which obviously fails)
or something equally stupid.
* test/lisp/calc/calc-tests.el (calc-test-solve-linear-system): New.
---
lisp/calc/calcalg2.el | 6 ++
test/lisp/calc/calc-tests.el | 103 +++++++++++++++++++++++++++++++++++
2 files changed, 109 insertions(+)
diff --git a/lisp/calc/calcalg2.el b/lisp/calc/calcalg2.el
index 18243bfc74..2a716633ae 100644
--- a/lisp/calc/calcalg2.el
+++ b/lisp/calc/calcalg2.el
@@ -2417,6 +2417,12 @@ math-try-solve-for
((= (length math-t1) 2)
(apply 'math-solve-linear
(car math-t2) math-try-solve-sign math-t1))
+ ((= (length math-t1) 1)
+ ;; Constant polynomial.
+ (if (eql (nth 2 math-t2) 1)
+ nil ; No possible solution.
+ ;; Root of the factor, if any.
+ (math-try-solve-for (nth 2 math-t2) 0 nil t)))
(math-solve-full
(math-poly-all-roots (car math-t2) math-t1))
(calc-symbolic-mode nil)
diff --git a/test/lisp/calc/calc-tests.el b/test/lisp/calc/calc-tests.el
index e1ee20b5d2..36a81dc2b7 100644
--- a/test/lisp/calc/calc-tests.el
+++ b/test/lisp/calc/calc-tests.el
@@ -215,6 +215,109 @@ calc-test-calendar
(should (equal (math-absolute-from-julian-dt -101 3 1) -36832))
(should (equal (math-absolute-from-julian-dt -4713 1 1) -1721425)))
+(ert-deftest calc-test-solve-linear-system ()
+ "Test linear system solving (bug#35374)."
+ ;; x + y = 3
+ ;; 2x - 3y = -4
+ ;; with the unique solution x=1, y=2
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 3)
+ (calcFunc-eq (- (* 2 (var x var-x)) (* 3 (var y var-y))) -4))
+ '(vec (var x var-x) (var y var-y)))
+ '(vec (calcFunc-eq (var x var-x) 1)
+ (calcFunc-eq (var y var-y) 2))))
+
+ ;; x + y = 1
+ ;; x + y = 2
+ ;; has no solution
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 1)
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 2))
+ '(vec (var x var-x) (var y var-y)))
+ '(calcFunc-solve
+ (vec
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 1)
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 2))
+ (vec (var x var-x) (var y var-y)))))
+ ;; x - y = 1
+ ;; x + y = 1
+ ;; with the unique solution x=1, y=0
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq (- (var x var-x) (var y var-y)) 1)
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 1))
+ '(vec (var x var-x) (var y var-y)))
+ '(vec (calcFunc-eq (var x var-x) 1)
+ (calcFunc-eq (var y var-y) 0))))
+ ;; 2x - 3y + z = 5
+ ;; x + y - 2z = 0
+ ;; -x + 2y + 3z = -3
+ ;; with the unique solution x=1, y=-1, z=0
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq
+ (+ (- (* 2 (var x var-x)) (* 3 (var y var-y))) (var z var-z))
+ 5)
+ (calcFunc-eq
+ (- (+ (var x var-x) (var y var-y)) (* 2 (var z var-z)))
+ 0)
+ (calcFunc-eq
+ (+ (- (* 2 (var y var-y)) (var x var-x)) (* 3 (var z var-z)))
+ -3))
+ '(vec (var x var-x) (var y var-y) (var z var-z)))
+ ;; The `float' forms in the result are just artefacts of Calc's
+ ;; current solver; it should be fixed to produce exact (integral)
+ ;; results in this case.
+ '(vec (calcFunc-eq (var x var-x) (float 1 0))
+ (calcFunc-eq (var y var-y) (float -1 0))
+ (calcFunc-eq (var z var-z) 0))))
+ ;; x = y + 1
+ ;; x = y
+ ;; has no solution
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq (var x var-x) (+ (var y var-y) 1))
+ (calcFunc-eq (var x var-x) (var y var-y)))
+ '(vec (var x var-x) (var y var-y)))
+ '(calcFunc-solve
+ (vec
+ (calcFunc-eq (var x var-x) (+ (var y var-y) 1))
+ (calcFunc-eq (var x var-x) (var y var-y)))
+ (vec (var x var-x) (var y var-y)))))
+ ;; x + y + z = 6
+ ;; x + y = 3
+ ;; x - y = 1
+ ;; with the unique solution x=2, y=1, z=3
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq (+ (+ (var x var-x) (var y var-y)) (var z var-z)) 6)
+ (calcFunc-eq (+ (var x var-x) (var y var-y)) 3)
+ (calcFunc-eq (- (var x var-x) (var y var-y)) 1))
+ '(vec (var x var-x) (var y var-y) (var z var-z)))
+ '(vec
+ (calcFunc-eq (var x var-x) 2)
+ (calcFunc-eq (var y var-y) 1)
+ (calcFunc-eq (var z var-z) 3))))
+ ;; x = 3
+ ;; x + 4y^2 = 3 (ok, so this one isn't linear)
+ ;; with the unique (double) solution x=3, y=0
+ (should (equal
+ (calcFunc-solve
+ '(vec
+ (calcFunc-eq (var x var-x) 3)
+ (calcFunc-eq (+ (var x var-x) (* 4 (^ (var y var-y) 2))) 3))
+ '(vec (var x var-x) (var y var-y)))
+ '(vec (calcFunc-eq (var x var-x) 3)
+ (calcFunc-eq (var y var-y) 0)))))
+
(provide 'calc-tests)
;;; calc-tests.el ends here
--
2.21.0 (Apple Git-122)
^ permalink raw reply related [flat|nested] 5+ messages in thread
* bug#35374: Calc; Div by 0 in solving system
2019-09-22 17:34 ` Mattias Engdegård
@ 2019-09-23 5:28 ` Christopher Howard
2019-09-23 10:11 ` Mattias Engdegård
0 siblings, 1 reply; 5+ messages in thread
From: Christopher Howard @ 2019-09-23 5:28 UTC (permalink / raw)
To: Mattias Engdegård, 35374
I am now using Emacs 26.2 (through Guix) but am able to reproduce the
original error in 26.2. I patched just this function (math-try-solve-
for) and reloaded it. The error went away, and the correct solution was generated.
I did not try running the tests.
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On Sun, 2019-09-22 at 19:34 +0200, Mattias Engdegård wrote:
> tags 35374 patch
> stop
>
> > Maybe someone more knowledgeable about Calc can help further.
>
> Much to our surprise, very few people volunteered their service. Now,
> despite being grossly under-qualified for the task, I did give it a
> go. After all, we can't have it fail on simple linear equation
> systems now can we.
>
> Please try this patch.
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* bug#35374: Calc; Div by 0 in solving system
2019-09-23 5:28 ` Christopher Howard
@ 2019-09-23 10:11 ` Mattias Engdegård
0 siblings, 0 replies; 5+ messages in thread
From: Mattias Engdegård @ 2019-09-23 10:11 UTC (permalink / raw)
To: Christopher Howard; +Cc: 35374
tags 35374 fixed
close 35374 26.4
stop
23 sep. 2019 kl. 07.28 skrev Christopher Howard <christopher.howard@qlfiles.net>:
>
> I am now using Emacs 26.2 (through Guix) but am able to reproduce the
> original error in 26.2. I patched just this function (math-try-solve-
> for) and reloaded it. The error went away, and the correct solution was generated.
Thanks for verifying! Pushed to emacs-26.
^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-04-23 14:34 ` bug#35374: Calc; Div by 0 in solving system Mattias Engdegård
2019-04-22 5:20 Christopher Howard
2019-09-22 17:34 ` Mattias Engdegård
2019-09-23 5:28 ` Christopher Howard
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