First implementation of real-valued linspace. #420

ejovo13 · 2021-05-31T10:57:06Z

Hi all,

This is my first time contributing on any project, ever, so bear with me if I make any missteps. As per issue #17, there seems to be a demand to implement some simple functions that return a range of values.

So, I implemented linspace using MATLAB's syntax as a guide. Currently there is no support for passing complex values into the function but if this pull request gets approved I will implement it ASAP. This pull request is a gentle attempt to make my first contribution and to understand the ropes before I start trying to tackle other open issues.

I didn't know how to implement a robust test for checking all of the elements in the returned rank 1 array, so I instead check the first and last values, and the length of the returned array in the test_linspace.f90 test.

Nevertheless, here is a quick demo when using the linspace function from another project which imports the fortran_stdlib:

jvdp1

Thank you and welcome!
A general comment: I wonder if such a procedure would find a better place in the module stdlib_linalg.
In Matlab it is in the same section as eye, diag,....

src/stdlib_stats.fypp

Split linspace into "default" and "n" function calls to avoid use of allocatable array

milancurcic · 2021-05-31T14:17:42Z

Thank you @ejovo13!

I wonder if such a procedure would find a better place in the module stdlib_linalg.

There's also stdlib_math which I think is more appropriate.

ejovo13 · 2021-05-31T19:06:36Z

As per @milancurcic 's advice, I refactored the linspace interface and implementation under the stdlib_math module.
As per @jvdp1 and @arjenmarkus 's guidance, I removed the allocatable attribute from the result array and broke the function up into two different signatures, one where you pass the length of the array and the other where linspace will use the module's private paramater DEFAULT_LINSPACE_LENGTH, currently set to 100

ejovo13 · 2021-05-31T22:32:30Z

Hello. I've implemented the functions logspace and lnspace, defined in submodules stdlib_math_logspace and stdlib_math_lnspace.

logspace

The logspace function mimicks the matlab implementation. The first two parameters are used to build the range from base^start to base^end. When base is not specified, use base 10. When the length, n, is not specified, output a rank 1 array of 50 elements.

The various function signatures of logspace (and linspace) are staggered and not using optional parameters for two reasons. The first is that using the length n as an optional parameter forces us to use allocatable arrays as our result, which should be avoided. Secondly, when using the base as an optional argument, the generic procedure is unable to distinguish function calls when the base is not passed.

this logspace implementation differs from MATLAB's because we can choose the base with which to generate the logarithmic space.

lnspace

lnspace is a special case of logspace when the base is equal to Euler's number e. Various levels of precision of EULERS_NUMBER are used in the stdlib_math module.

Tests

Running make test will check certain qualities about the results and will output a few select log files showing the arrays generated from their calls for manual inspection. Here is a gist that shows sample output.

arjenmarkus · 2021-06-01T09:28:06Z

How about a similar function that returns points based on a geometric series? Note: that would require an extra parameter - the ratio between adjacent intervals. Op di 1 jun. 2021 om 00:32 schreef Evan Voyles ***@***.***>:

…

Hello. I've implemented the functions logspace and lnspace, defined in submodules stdlib_math_logspace and stdlib_math_lnspace. logspace The logspace function mimicks the matlab implementation. The first two parameters are used to build the range from base^start to base^end. When base is not specified, use base 10. When the length, n, is not specified, output a rank 1 array of 50 elements. The various function signatures of logspace (and linspace) are staggered and not using optional parameters for two reasons. The first is that using the length n as an optional parameter forces us to use allocatable arrays as our result, which should be avoided. Secondly, when using the base as an optional argument, the generic procedure is unable to distinguish function calls when the base is not passed. this logspace implementation differs from MATLAB's because we can choose the base with which to generate the logarithmic space. lnspace lnspace is a special case of logspace when the base is equal to Euler's number e. Various levels of precision of EULERS_NUMBER are used in the stdlib_math module. Tests Running make test will check certain qualities about the results and will output a few select log files showing the arrays generated from their calls for manual inspection. Here is a gist <https://gist.github.com/ejovo13/c0ea7b4eefe97d1ddf0c485e8048cc20> that shows sample output. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#420 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN6YR7UMJI3SBHKBWWUF5LTQQFATANCNFSM452VE52A> .

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Requested changes addressed

src/stdlib_math.fypp

Demand a lower tolerance value for higher precision tests

Co-authored-by: Sebastian Ehlert <28669218+awvwgk@users.noreply.github.com>

ejovo13 · 2021-07-12T21:02:58Z

Well, I believe that I've addressed, on my side, all of your comments. What I thought was going to be a quick and easy first PR has dragged on (not that that's a bad thing) and generated a lot of fruitful discussion. Thank you to everyone for their contributions and suggestions to improve this PR.

Apart from a few unresolved discussions, I don't believe that there is anything left for me to do. The ball is in your court and I will wait for any further direction. Thank you all.

jvdp1

LGTM.
I approve it, pending a few minor comments.
Regarding the checks, I would prefer checks on the absolute values, instead of on relative values. But I leave that for the next reviewer.

doc/specs/stdlib_math.md

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

awvwgk

Pending any unresolved requests, this looks ready to be part of stdlib. Thanks a lot for sharing this contribution.

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

jvdp1 · 2021-07-14T20:18:47Z

@ivan-pi @milancurcic you commented this PR. Could you check if your comments were answered appropriately, and appove this PR if it is ok, please?

jvdp1

Some details in the docs

src/stdlib_math.fypp

milancurcic

Thank you, great addition. I only left one nit-pick about labeled format statements in test subroutines.

src/tests/math/test_linspace.f90

ejovo13 added 8 commits May 31, 2021 11:51

Add linspace submodule to stdlib_stats

affa81a

Verify that linspace generates the proper spread

7d7a992

Add linspace and object dependencies

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libspace function source code

b42b4fc

Add linspace to public api

4db9cca

Update test to include negative integer for elements requested

3040135

Fix manual dependency

4257b4e

Add real conversions to integer arithmetic

87fde22

awvwgk added idea Proposition of an idea and opening an issue to discuss it reviewers needed This patch requires extra eyes and removed idea Proposition of an idea and opening an issue to discuss it labels May 31, 2021

awvwgk requested review from certik, ivan-pi and milancurcic May 31, 2021 11:29

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ejovo13 added 5 commits May 31, 2021 14:40

Refactor stdlib_stats_linspace -> stdlib_linalg_linspace;

3db3357

Split linspace into "default" and "n" function calls to avoid use of allocatable array

Make linspace public and add DEFAULT_LINSPACE_LENGTH parameter

6e42249

Fix whitespace indentation that I interrupted

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Refactor linspace manual dependencies

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Remove linspace public export

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ejovo13 added 3 commits May 31, 2021 19:48

Remove linspace from stdlib_linalg

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Refactor linspace interface to stdlib_math

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Remove linspace test from linalgebra folder

acd695e

ejovo13 added 2 commits June 1, 2021 00:16

Add logspace and lnspace functions in stdlib_math

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Modify function behvaior on input n = 1

598287b

Fix printed function call

f8dbe00

ejovo13 and others added 6 commits July 12, 2021 13:55

Update src/tests/math/test_linspace.f90

f9a6623

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Update src/tests/math/test_linspace.f90

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Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Update src/stdlib_math.fypp

905dc28

Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Update src/stdlib_math.fypp

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Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Update src/stdlib_math.fypp

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Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Add more comprehensive documentation

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awvwgk reviewed Jul 12, 2021

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ejovo13 and others added 2 commits July 12, 2021 16:37

Add appropriate tolerance level

d428ad8

Demand a lower tolerance value for higher precision tests

Update src/stdlib_math.fypp

dd4e935

Co-authored-by: Sebastian Ehlert <28669218+awvwgk@users.noreply.github.com>

ejovo13 requested review from jvdp1 and awvwgk July 12, 2021 21:10

jvdp1 approved these changes Jul 13, 2021

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ejovo13 and others added 2 commits July 13, 2021 21:16

Update doc/specs/stdlib_math.md

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Co-authored-by: Jeremie Vandenplas <jeremie.vandenplas@gmail.com>

Update doc/specs/stdlib_math.md

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awvwgk approved these changes Jul 14, 2021

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ejovo13 and others added 3 commits July 14, 2021 10:01

Update doc/specs/stdlib_math.md

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Update doc/specs/stdlib_math.md

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Update doc/specs/stdlib_math.md

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jvdp1 approved these changes Jul 14, 2021

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milancurcic approved these changes Jul 15, 2021

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jvdp1 and others added 4 commits July 20, 2021 13:56

Update src/stdlib_math.fypp

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Update src/stdlib_math.fypp

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Merge branch 'fortran-lang:master' into lin_log_space

5708e01

Clean up format statements

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jvdp1 merged commit 233d871 into fortran-lang:master Jul 20, 2021

ejovo13 deleted the lin_log_space branch July 20, 2021 20:17

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First implementation of real-valued linspace. #420

First implementation of real-valued linspace. #420

ejovo13 commented May 31, 2021

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First implementation of real-valued linspace. #420

First implementation of real-valued linspace. #420

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logspace

lnspace

Tests

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