# Possible bug while calculating determinant?
**URL:** https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960
**Category:** Specific Domains
**Tags:** linearalgebra
**Created:** [March 14, 2020, 8:54am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960 "2020-03-14T08:54:38Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@PseudoCodeNerd](https://discourse.julialang.org/u/PseudoCodeNerd)
#### Post date: [March 14, 2020, 8:54am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/1 "2020-03-14T08:54:38Z")
Hello
I’m a high school junior and was recently self-studying linear algebra. I was reading about calculating determinants and the properties of them.
I read that whenever in a determinant, there are 2 similar rows (or columns), then the determinant value must be zero.
I have a habit of trying out all my math in julia too, so I wrote
```julia
julia> a = [1 2 3 7; 4 1 7 2; 5 7 1 9; 1 2 3 7]
4×4 Array{Int32,2}:
1 2 3 7
4 1 7 2
5 7 1 9
1 2 3 7
julia> det(a)
4.168280304250871e-14
```
I’m surprised why didn’t it return zero but a very small number (maybe tending towards zero ?)
Thanks
---
### Author:  [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [March 14, 2020, 9:08am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/2 "2020-03-14T09:08:42Z")
```julia
julia> a
4×4 Array{Int64,2}:
1 2 3 7
4 1 7 2
5 7 1 9
1 2 3 7
julia> det(a)
0.0
julia> a = convert(Array{Int32}, a)
4×4 Array{Int32,2}:
1 2 3 7
4 1 7 2
5 7 1 9
1 2 3 7
julia> det(a)
0.0
julia> versioninfo()
Julia Version 1.3.1
Commit 2d5741174c (2019-12-30 21:36 UTC)
Platform Info:
OS: Linux (x86_64-linux-gnu)
CPU: Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz
WORD_SIZE: 64
LIBM: libopenlibm
LLVM: libLLVM-6.0.1 (ORCJIT, skylake)
Environment:
JULIA_NUM_THREADS = 4
```
What julia version are vou on?
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [March 14, 2020, 9:15am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/3 "2020-03-14T09:15:42Z")
Although (like @Sukera) I cannot replicate this using a recent Julia version, note that [floating point arithmetic has some special properties you should be aware of](https://discourse.julialang.org/t/psa-floating-point-arithmetic/8678).
If you are following along the calculations in a linear algebra text, you may want to convert to a type that is closed under the operations required for the determinant, eg
```julia
julia> det(Rational.(a))
0//1
```
(Incidentally, I would recommend [textbooks that place less emphasis on the determinant](http://linear.axler.net/)).
---
### Author:  [@PseudoCodeNerd](https://discourse.julialang.org/u/PseudoCodeNerd)
#### Post date: [March 14, 2020, 9:20am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/4 "2020-03-14T09:20:37Z")
This is weird
Im on 1.0.4 the LTS version
I tried with numpy still didn’t get zero.
---
### Author:  [@JeffreySarnoff](https://discourse.julialang.org/u/JeffreySarnoff)
#### Post date: [March 14, 2020, 10:04am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/5 "2020-03-14T10:04:38Z")
What does `julia> versioninfo()` say?
Do you get the same result if you first restart your computer?
---
### Author:  [@PseudoCodeNerd](https://discourse.julialang.org/u/PseudoCodeNerd)
#### Post date: [March 14, 2020, 10:59am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/6 "2020-03-14T10:59:51Z")
Here it is
```julia
julia> versioninfo()
Julia Version 1.0.4
Commit 38e9fb7f80 (2019-05-16 03:38 UTC)
Platform Info:
OS: Linux (i686-pc-linux-gnu)
CPU: Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz
WORD_SIZE: 32
LIBM: libopenlibm
LLVM: libLLVM-6.0.0 (ORCJIT, skylake)
```
---
### Author:  [@Mason](https://discourse.julialang.org/u/Mason)
#### Post date: [March 14, 2020, 11:16am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/7 "2020-03-14T11:16:39Z")
I find it a little surprising that Julia converts to floating point here given that the input array was full of `Int`s.
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [March 14, 2020, 11:24am UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/8 "2020-03-14T11:24:05Z")
cf [Possible bug in determinant calculation - #8 by stevengj](https://discourse.julialang.org/t/possible-bug-in-determinant-calculation/20323/8).
---
### Author:  [@StefanKarpinski](https://discourse.julialang.org/u/StefanKarpinski)
#### Post date: [March 14, 2020, 3:46pm UTC](https://discourse.julialang.org/t/possible-bug-while-calculating-determinant/35960/9 "2020-03-14T15:46:47Z")
There’s no efficient way to compute exact integer determinants.