1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
package forces
import (
"../structs"
"fmt"
"git.darknebu.la/bit/logplus"
"gopkg.in/cheggaaa/pb.v1"
"math"
)
// forces_acting calculates the force inbetween the two given stars s1 and s2
// The function return the force
func accelerationActing(s1 structs.Star2D, s2 structs.Star2D) structs.Vec2 {
// Gravitational constant
var G = 6.674E-11
// the vector from star s1 to star s2
var r12 = s2.C.Subtract(s1.C)
// the distance between the stars
var deltaR = r12.GetLength()
// Define the vector components (scalar and direction)
scalarA := G * (s2.M) / math.Pow(deltaR, 2)
directionVectorA := r12.GetDirVector()
// Combine the sacalar and the firection vector resulting in a vector defining the
// acceleration of the star
A := directionVectorA.Multiply(scalarA)
return A
}
// accelerations calculates the acceleration acting in between a given star and all the other stars in a given array.
func accelerations(stars_arr []structs.Star2D, nr int) structs.Vec2 {
// Acceleration structure
var accelerationStructure = structs.Vec2{}
// Iterate over all the stars in the stars_arr
for index := range stars_arr {
// If the current star is not the star itself
if index != nr {
// calculate the acceleration and add it to the overall acceleration of the star
aa := accelerationActing(stars_arr[nr], stars_arr[index])
accelerationStructure = accelerationStructure.Add(aa)
}
}
return accelerationStructure
}
// accelerationThread calculates the acceleration acting on a given amount of stars in a given range for a given slice of stars
// utilizing go-methods
func accelerationThread(starSlice []structs.Star2D, localRangeStart int, localRangeEnd int, channel chan structs.Star2D) {
// iterate over the given range
for index := localRangeStart; index < localRangeEnd; index++ {
// Calculate the acceleration acting inbetween the given star and all other stars
var a = accelerations(starSlice, index)
// create a new star
newStar := starSlice[index].Copy()
newStar.AccelerateVelocity(a, 1)
// push the new Star into the channel
channel <- newStar
}
}
// CalcAllAccelerations calculates all the accelerations acting in between all the stars in the given starSlice slice and
// returns a "new" slice containing the stars with their new velocities
func CalcAllAccelerations(starSlice []structs.Star2D, threads int) []structs.Star2D {
// create a channel for bundling the stars generated in the go-methods
channel := make(chan structs.Star2D, 1000)
sliceLength := len(starSlice)
// calculate the local range
// Example: 100 stars with 4 threads = 25 stars per thread
localRangeLen := sliceLength / threads
// generate a new slice for storing the stars
var newSlice []structs.Star2D
logplus.LogNeutral(fmt.Sprintf("Starting %d workers, each processing %d stars", threads, localRangeLen))
// start n go-methods each covering a part of the whole slice
for i := 0; i < threads; i++ {
// define the local range
localRangeStart := i * localRangeLen
localRangeEnd := (i * localRangeLen) + localRangeLen
// calculate the accelerations for all the stars in the given slice in the given range and return them using the
// given channel
go accelerationThread(starSlice, localRangeStart, localRangeEnd, channel)
}
// Handle errors (10004 stars, but 1250 stars per thread, so 4 stars are not calculate and block the queue)
if sliceLength > localRangeLen {
// Calculate the amount of stars and their range
remainingStars := sliceLength - (localRangeLen * threads)
localRangeEnd := ((threads - 1) * localRangeLen) + localRangeLen
// Run the Thread
// go accelerationThread(starSlice, localRangeEnd, localRangeEnd+remainingStars, channel)
accelerationThread(starSlice, localRangeEnd, localRangeEnd+remainingStars, channel)
}
// Initialize a new progress bar
bar := pb.New(len(starSlice)).Prefix("Stars: ")
bar.Start()
// iterate over the amount of stars
for i := 0; i < sliceLength; i++ {
// block until a star is finisehd
var newStar = <-channel
// append the star from the channel to the newSlice for returning in the end
newSlice = append(newSlice, newStar)
// increment the progress bar and the counter
bar.Increment()
}
bar.Finish()
return newSlice
}
// Calculate the new positions of the stars using the
func NextTimestep(starSlice []structs.Star2D, deltat float64) []structs.Star2D {
// create a new slice for storing the "new" stars
var newSlice []structs.Star2D
// iterate over all the stars in the old slice
for index := range starSlice {
// move the star with it's velocity for time deltat
newStar := starSlice[index].Copy()
newStar.Move(deltat)
// append the new star to the newSlice
newSlice = append(newSlice, newStar)
}
return newSlice
}
|
