[GSoC] solve method for cable class #25461

Ishanned · 2023-08-02T09:36:22Z

References to other Issues or PRs

Brief description of what is fixed or changed

Implemented the solve method for the cable class. For point loads, this method computes the tensions in the segments of the cable, the reaction forces at the supports and updates the length. For distributed load, this method computes the tension at each point using tension_at() method, and the reaction forces at the supports.

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Release Notes

physics.continuum_mechanics
- solve method implemented in the cable class

sympy-bot · 2023-08-02T09:36:30Z

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physics.continuum_mechanics
- solve method implemented in the cable class (#25461 by @Ishanned and @shishir-11)

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#### Brief description of what is fixed or changed
Implemented the solve method for the cable class. For point loads, this method computes the tensions in the segments of the cable, the reaction forces at the supports and updates the length. For distributed load, this method computes the tension at each point using tension_at() method, and the reaction forces at the supports.

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Update

The release notes on the wiki have been updated.

Ishanned · 2023-08-02T11:55:40Z

@Psycho-Pirate @AdvaitPote please have a look

AdvaitPote · 2023-08-05T11:42:16Z

sympy/physics/continuum_mechanics/cable.py

+            x1 = self._left_support[0]
+            y1 = self._left_support[1]
+
+            theta = -atan((y2 - y1)/(x2 - x1))


Try changing the name of this variable to a more descriptive one

…cable-solve "merged remote branch to local"

AdvaitPote · 2024-02-25T18:38:25Z

Just closed and reopened to run the tests again.

JebronLames32 · 2024-03-20T18:39:27Z

Hello @Ishanned @AdvaitPote
I have a few doubts about what has been coded here. While creating a point load, we are mentioning the positions at which the point loads are acting.

sympy/sympy/physics/continuum_mechanics/cable.py

Lines 353 to 354 in afc9fd2

    
           x = sympify(load[1]) 
        
           y = sympify(load[2])

However, I feel this should not be done and the force should just be given an x coordinate as the attribute with an optional y attribute. This is because the user will then be allowed to create cases which will be practally wrong. For example, the case:

should not be technically possible. We should return errors when such inputs are provided. I think we should allow only one of the y coordinates of the loads to be given as inputs and calculate the location of the y coordinates of the remaining loads ourselves.

Another thing I noticed is that while calculating the tension and reaction forces for the uniformly distributed load, we are taking the coordinates of the lowest point of the cable as inputs and later checking if the lowest point is consistent with the supports.

sympy/sympy/physics/continuum_mechanics/cable.py

Lines 541 to 543 in afc9fd2

    
           lowest_x = sympify(args[0]) 
        
           lowest_y = sympify(args[1]) 
        
           self._lowest_x_global = lowest_x

I feel we could be only taking the length of sag of the cable (y coordinate) as input and calculate the x coordinate ourselves with something like the code:

from sympy import sqrt

lowest_y = sympify(args[0])
x1 = self._left_support[0]
y1 = self._left_support[1]
x2 = self._right_support[0]
y2 = self._right_support[1]
lowest_x = self.length / (sqrt( (y1 - lowest_y) / (y2 - lowest_y) ) + 1)

I have solved for the tensions and reaction forces myself using vectors (sympy.physics.vector) instead of plain trigonometry. For representing the tension caused due to point loads, I have used the (Piecewise) function. The reason I tried using vectors is because I felt they looked more understandable and could be more flexibly applied to calculate certain other properties of the cable in the future. I did want to clarify the above doubts before I made a pull request for you to view my code as I felt these were important points.

AdvaitPote · 2024-05-15T07:09:04Z

@Ishanned Let's prioritize closing/merging this PR before the GSoC coding period starts.

Also, @JebronLames32 your points are valid. @Ishanned kindly see if you can add those changes as well.

Ishanned · 2024-05-16T07:27:03Z

Hey @AdvaitPote, I'll soon take care of the precision errors that are causing the tests to fail.
Also, I am a bit occupied currently, so I might not be able to make the changes that @JebronLames32 has suggested. If @JebronLames32 wishes, you can make a new PR for this issue once we have sorted this one. Else, maybe @shishir-11 can take up this issue since he is going to be working on this sub-module over the summer. Let me know whoever wants to take this up, I would certainly be taking part in the discussions.

shishir-11 · 2024-05-18T16:06:46Z

I have a few questions about calculating the y coordinates for distributed loads . Can we guess the shape of the cable or its equation. If its y coordinates form a quadratic equation we would not need to pass a lowest y coordinate on our own.

We might be able to use or some similar formula

$$ y_{1} = ax_{1}^{2} + bx_{1}+c $$

$$ y_{2} = ax_{2}^{2} + bx_{2}+c $$

$$ length = \sqrt{1+(\frac{dy}{dx})^{2}} $$

We would be able to calculate the coordinates of the lowest point. Please correct me if I'm wrong.
Also Since we already have the tensions in each segment , at each X coordinate where forces are applied we can use

$$ T_{1}\sin\theta_{1} - T_{2}\sin\theta_{2} + F_{x} = 0 $$

$$ T_{1}\cos\theta_{1} + T_{2}\cos\theta_{2} + F_{y} = 0 $$

Where $\theta$ is the angle of cable with vertical. We can use these angles to find the y positions of each force ? Any thought on this @AdvaitPote @Ishanned

shishir-11 · 2024-05-26T15:24:01Z

Another thing I noticed is that while calculating the tension and reaction forces for the uniformly distributed load, we are taking the coordinates of the lowest point of the cable as inputs and later checking if the lowest point is consistent with the supports.

Since we aren't taking the length of the cable from the user for calculation , The current code works fine. I'm unable to find a method to implement what @JebronLames32 initially asked for , so i would like to request if there is any content or formula present to achieve it.

Change Values for doctests

Replace cable Mailmap with sympy master branch

github-actions · 2024-05-29T17:07:32Z

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

| Change   | Before [a36a8b23]    | After [2eb826cd]    |   Ratio | Benchmark (Parameter)                                                |
|----------|----------------------|---------------------|---------|----------------------------------------------------------------------|
| -        | 69.7±1ms             | 43.5±0.07ms         |    0.62 | integrate.TimeIntegrationRisch02.time_doit(10)                       |
| -        | 67.5±0.8ms           | 42.7±0.3ms          |    0.63 | integrate.TimeIntegrationRisch02.time_doit_risch(10)                 |
| +        | 19.0±0.2μs           | 30.4±0.3μs          |    1.6  | integrate.TimeIntegrationRisch03.time_doit(1)                        |
| -        | 5.47±0.05ms          | 2.88±0.03ms         |    0.53 | logic.LogicSuite.time_load_file                                      |
| -        | 73.7±0.4ms           | 28.8±0.3ms          |    0.39 | polys.TimeGCD_GaussInt.time_op(1, 'dense')                           |
| -        | 26.3±0.3ms           | 17.0±0.08ms         |    0.65 | polys.TimeGCD_GaussInt.time_op(1, 'expr')                            |
| -        | 74.0±0.3ms           | 28.7±0.1ms          |    0.39 | polys.TimeGCD_GaussInt.time_op(1, 'sparse')                          |
| -        | 262±1ms              | 125±0.5ms           |    0.48 | polys.TimeGCD_GaussInt.time_op(2, 'dense')                           |
| -        | 257±2ms              | 123±0.5ms           |    0.48 | polys.TimeGCD_GaussInt.time_op(2, 'sparse')                          |
| -        | 675±5ms              | 370±2ms             |    0.55 | polys.TimeGCD_GaussInt.time_op(3, 'dense')                           |
| -        | 660±1ms              | 369±0.7ms           |    0.56 | polys.TimeGCD_GaussInt.time_op(3, 'sparse')                          |
| -        | 495±9μs              | 287±0.8μs           |    0.58 | polys.TimeGCD_LinearDenseQuadraticGCD.time_op(1, 'dense')            |
| -        | 1.79±0.03ms          | 1.08±0.01ms         |    0.6  | polys.TimeGCD_LinearDenseQuadraticGCD.time_op(2, 'dense')            |
| -        | 5.89±0.09ms          | 3.06±0.02ms         |    0.52 | polys.TimeGCD_LinearDenseQuadraticGCD.time_op(3, 'dense')            |
| -        | 445±2μs              | 231±2μs             |    0.52 | polys.TimeGCD_QuadraticNonMonicGCD.time_op(1, 'dense')               |
| -        | 1.48±0.02ms          | 678±2μs             |    0.46 | polys.TimeGCD_QuadraticNonMonicGCD.time_op(2, 'dense')               |
| -        | 4.88±0.01ms          | 1.68±0.02ms         |    0.35 | polys.TimeGCD_QuadraticNonMonicGCD.time_op(3, 'dense')               |
| -        | 377±0.4μs            | 205±1μs             |    0.54 | polys.TimeGCD_SparseGCDHighDegree.time_op(1, 'dense')                |
| -        | 2.44±0.02ms          | 1.24±0.01ms         |    0.51 | polys.TimeGCD_SparseGCDHighDegree.time_op(3, 'dense')                |
| -        | 10.00±0.03ms         | 4.37±0.08ms         |    0.44 | polys.TimeGCD_SparseGCDHighDegree.time_op(5, 'dense')                |
| -        | 359±3μs              | 168±0.9μs           |    0.47 | polys.TimeGCD_SparseNonMonicQuadratic.time_op(1, 'dense')            |
| -        | 2.49±0.01ms          | 896±5μs             |    0.36 | polys.TimeGCD_SparseNonMonicQuadratic.time_op(3, 'dense')            |
| -        | 9.52±0.08ms          | 2.66±0.03ms         |    0.28 | polys.TimeGCD_SparseNonMonicQuadratic.time_op(5, 'dense')            |
| -        | 1.04±0.01ms          | 426±2μs             |    0.41 | polys.TimePREM_LinearDenseQuadraticGCD.time_op(3, 'dense')           |
| -        | 1.75±0.01ms          | 505±1μs             |    0.29 | polys.TimePREM_LinearDenseQuadraticGCD.time_op(3, 'sparse')          |
| -        | 5.90±0.03ms          | 1.81±0.02ms         |    0.31 | polys.TimePREM_LinearDenseQuadraticGCD.time_op(5, 'dense')           |
| -        | 8.48±0.06ms          | 1.47±0.01ms         |    0.17 | polys.TimePREM_LinearDenseQuadraticGCD.time_op(5, 'sparse')          |
| -        | 289±0.9μs            | 64.9±0.4μs          |    0.22 | polys.TimePREM_QuadraticNonMonicGCD.time_op(1, 'sparse')             |
| -        | 3.42±0.02ms          | 391±6μs             |    0.11 | polys.TimePREM_QuadraticNonMonicGCD.time_op(3, 'dense')              |
| -        | 3.96±0.03ms          | 281±3μs             |    0.07 | polys.TimePREM_QuadraticNonMonicGCD.time_op(3, 'sparse')             |
| -        | 6.98±0.05ms          | 1.28±0.01ms         |    0.18 | polys.TimePREM_QuadraticNonMonicGCD.time_op(5, 'dense')              |
| -        | 8.76±0.07ms          | 839±3μs             |    0.1  | polys.TimePREM_QuadraticNonMonicGCD.time_op(5, 'sparse')             |
| -        | 5.02±0.01ms          | 3.00±0.03ms         |    0.6  | polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(2, 'sparse') |
| -        | 12.0±0.1ms           | 6.58±0.03ms         |    0.55 | polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(3, 'dense')  |
| -        | 22.6±0.2ms           | 9.03±0.05ms         |    0.4  | polys.TimeSUBRESULTANTS_LinearDenseQuadraticGCD.time_op(3, 'sparse') |
| -        | 5.29±0.03ms          | 865±4μs             |    0.16 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(1, 'sparse')    |
| -        | 12.7±0.1ms           | 6.99±0.01ms         |    0.55 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(2, 'sparse')    |
| -        | 103±2ms              | 25.8±0.09ms         |    0.25 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(3, 'dense')     |
| -        | 166±1ms              | 53.9±0.2ms          |    0.32 | polys.TimeSUBRESULTANTS_QuadraticNonMonicGCD.time_op(3, 'sparse')    |
| -        | 176±0.3μs            | 112±0.9μs           |    0.64 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(1, 'dense')      |
| -        | 362±2μs              | 217±0.9μs           |    0.6  | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(1, 'sparse')     |
| -        | 4.30±0.01ms          | 836±4μs             |    0.19 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(3, 'dense')      |
| -        | 5.29±0.05ms          | 381±2μs             |    0.07 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(3, 'sparse')     |
| -        | 20.2±0.3ms           | 2.80±0.01ms         |    0.14 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(5, 'dense')      |
| -        | 23.0±0.05ms          | 626±2μs             |    0.03 | polys.TimeSUBRESULTANTS_SparseGCDHighDegree.time_op(5, 'sparse')     |
| -        | 480±2μs              | 134±0.8μs           |    0.28 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(1, 'sparse') |
| -        | 4.66±0.02ms          | 609±7μs             |    0.13 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(3, 'dense')  |
| -        | 5.41±0.06ms          | 141±0.7μs           |    0.03 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(3, 'sparse') |
| -        | 13.8±0.2ms           | 1.27±0ms            |    0.09 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(5, 'dense')  |
| -        | 14.2±0.07ms          | 142±2μs             |    0.01 | polys.TimeSUBRESULTANTS_SparseNonMonicQuadratic.time_op(5, 'sparse') |
| -        | 137±1μs              | 76.1±0.4μs          |    0.56 | solve.TimeMatrixOperations.time_rref(3, 0)                           |
| -        | 258±2μs              | 90.5±0.8μs          |    0.35 | solve.TimeMatrixOperations.time_rref(4, 0)                           |
| -        | 24.6±0.1ms           | 10.3±0.03ms         |    0.42 | solve.TimeSolveLinSys189x49.time_solve_lin_sys                       |
| -        | 28.6±0.1ms           | 15.4±0.06ms         |    0.54 | solve.TimeSparseSystem.time_linsolve_Aaug(20)                        |
| -        | 55.4±0.2ms           | 24.8±0.1ms          |    0.45 | solve.TimeSparseSystem.time_linsolve_Aaug(30)                        |
| -        | 28.3±0.2ms           | 15.2±0.07ms         |    0.54 | solve.TimeSparseSystem.time_linsolve_Ab(20)                          |
| -        | 55.5±0.4ms           | 24.4±0.08ms         |    0.44 | solve.TimeSparseSystem.time_linsolve_Ab(30)                          |

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

Ishanned · 2024-05-29T17:10:02Z

@AdvaitPote have a look. Also thanks @shishir-11 for helping me fix the precision error :)

AdvaitPote · 2024-05-29T17:33:25Z

Cool. It has already been discussed that the priority should be to merge this PR so that @shishir-11 can get started with his project.
Any bugs or potential changes mentioned by @JebronLames32 can be added in the future as an extended goal.

Ishanned and others added 3 commits August 1, 2023 20:46

dummy commit

e9c7c9a

changes in tests

4fa3cbd

Merge branch 'sympy:master' into cable-solve

b724992

AdvaitPote added the physics.continuum_mechanics label Aug 3, 2023

AdvaitPote reviewed Aug 5, 2023

View reviewed changes

Ishanned added 4 commits August 26, 2023 12:59

added solve for distributed loads

145b374

Merge branch 'cable-solve' of https://github.com/Ishanned/sympy into …

de11cf8

…cable-solve "merged remote branch to local"

removed unused imports

e794f03

fixed precision error

afc9fd2

Ishanned changed the title ~~[GSoC] solve method for point loads in cable class~~ [GSoC] solve method for cable class Aug 26, 2023

AdvaitPote mentioned this pull request Feb 25, 2024

Implemented the solve method for the cable class #26272

Closed

AdvaitPote closed this Feb 25, 2024

AdvaitPote reopened this Feb 25, 2024

Change Values for accuracy tests

a721825

Ishanned and others added 3 commits May 28, 2024 22:05

Merge pull request #1 from shishir-11/cable-solve

77da3e0

Change Values for doctests

Replace cable Mailmap with sympy master branch

d6af67e

Merge pull request #2 from shishir-11/cable-solve

53f60db

Replace cable Mailmap with sympy master branch

github-actions bot added the Merge conflict label May 29, 2024

Merge branch 'master' into cable-solve

3cd6098

github-actions bot removed the Merge conflict label May 29, 2024

AdvaitPote merged commit 8c94201 into sympy:master May 29, 2024

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