# Debugging, but code in conjugate gradient implementation. 

**URL:** <https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884>\
**Category:** Optimization (Mathematical)\
**Created:** [March 22, 2018, 9:59am UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884 "2018-03-22T09:59:58Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Marcom](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/marcom/32/3779_2.png) [@Marcom](https://discourse.julialang.org/u/Marcom)\
**Post date:** [March 22, 2018, 9:59am UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884/1 "2018-03-22T09:59:58Z")

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Not sure this is the right place, but there seems to be an issue with how Julia is interpreting the inputs of a function. I am certain my code is correct as far as implementation of the problem statement. However, I keep getting the error at the bottom “MethodError: no method matching colon(::Int64, ::Tuple{Int64})”. Why is Julia interpreting some inputs as a tuple and one float?

 ![Capture1](https://global.discourse-cdn.com/julialang/original/3X/d/8/d88be16dfcff3dbeaf657fd2ea7d3510546717f6.png) ![Capture](https://global.discourse-cdn.com/julialang/original/3X/1/2/127c5a881e2bdfce16a5cf1d9642cfc4a00832bf.png)

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**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [March 22, 2018, 10:03am UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884/2 "2018-03-22T10:03:12Z")

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![20180322_110201](https://global.discourse-cdn.com/julialang/original/3X/4/a/4a8854f1ba86135efb1b6ac54082929455930238.jpeg)

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**Author:** ![pfitzseb](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pfitzseb/32/45566_2.png) [@pfitzseb](https://discourse.julialang.org/u/pfitzseb)\
**Post date:** [March 22, 2018, 10:20am UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884/3 "2018-03-22T10:20:09Z")

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`N` will _always_ be a tuple in `N = size(U)` – you probably want something like `size(U, 1)` or `length(U)`.

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**Author:** ![rveltz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rveltz/32/2707_2.png) [@rveltz](https://discourse.julialang.org/u/rveltz)\
**Post date:** [March 22, 2018, 11:35am UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884/4 "2018-03-22T11:35:24Z")

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That’s some high quality photo for such piece of text 😉

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**Author:** ![y4lu](https://avatars.discourse-cdn.com/v4/letter/y/47e85d/32.png) [@y4lu](https://discourse.julialang.org/u/y4lu)\
**Post date:** [March 22, 2018, 1:14pm UTC](https://discourse.julialang.org/t/debugging-but-code-in-conjugate-gradient-implementation/9884/5 "2018-03-22T13:14:51Z")

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`N = size(U, 1)`