An example of what I desire:
local X = {["Alpha"] = 5, ["Beta"] = this.Alpha+3}
print(X.Beta) --> error: [string "stdin"]:1: attempt to index global 'this' (a nil value)
is there a way to get this working, or a substitute I can use without too much code bloat(I want it to look presentable, so fenv hacks are out of the picture)
if anyone wants to take a crack at lua, repl.it is a good testing webpage for quick scripts
No there is no way to do this because the table does not yet exist and there is no notion of "self" in Lua (except via syntactic sugar for table methods). You have to do it in two steps:
local X = {["Alpha"] = 5}
X["Beta"] = X.Alpha+3
Note that you only need the square brackets if your key is not a string or if it is a string with characters other than any of [a-z][A-Z][0-9]_.
local X = {Alpha = 5}
X.Beta = X.Alpha+3
Update:
Based on what I saw on your pastebin, you probably should do this slightly differently:
local Alpha = 5
local X = {
Alpha = Alpha,
Beta = Alpha+3,
Gamma = someFunction(Alpha),
Eta = Alpha:method()
}
(obviously Alpha has no method because in the example it is a number but you get the idea, just wanted to show if Alpha were an object).
Related
I'm following this tutorial in order to try and do an FEA of a model.msh that I have to see how it would deform given different external forces in different places.
There they define the weak form as
a(u,v) = ∫( ε(v) ⊙ (σ∘ε(u)) )*dΩ
l(v) = 0
and they state "The linear form is simply l(v) = 0 since there are not external forces in this example."
As mentioned, I would like to analyse the different deformation that different external forces would cause on my model, but I can't seem to find anywhere an example of this. Could someone help me on defining this linear form for external forces different than 0?
Thanks.
Maybe this helps you out. It was written in a hurry, so please do not mind if you encounter spelling mistakes or other beauty issues :)
# define where the output shall go
output_Path ="Output/3_Gridap/1_Lin_FEA/FE_8"
mkpath(output_Path)
output_Name ="pde_6"
using Gridap
# please load the model that is shown in: https://gridap.github.io/Tutorials/dev/pages/t001_poisson/
model = DiscreteModelFromFile("Code/Meshes/Data/possion.json")
# just in case you want to see the model using paraview
writevtk(model,"$(output_Path)/md")
order = 1
reffe = ReferenceFE(lagrangian,VectorValue{3,Float64},order)
V0 = TestFESpace(model,reffe;
conformity=:H1,
# to see which elements belongs to "bottom" open the model which is saved through "writevtk(model,"$(output_Path)/md")"
dirichlet_tags=["bottom"],
# activate/deactivate the boundary conditions
dirichlet_masks=[
(true, true, true), # clamp the bottom
])
# define displacement
clamping(x) = VectorValue(0.0,0.0,0.0)
U = TrialFESpace(V0,[clamping])
const E = 7e+7
const ν = 0.33
const λ = (E*ν)/((1+ν)*(1-2*ν))
const μ = E/(2*(1+ν))
σ(ε) = λ*tr(ε)*one(ε) + 2*μ*ε
degree = 2*order
Ω = Triangulation(model)
dΩ = Measure(Ω,degree)
# Neumann boundary conditions
# here we define the surface on which we want an external force
Γ_Tr = BoundaryTriangulation(model,tags=["triangle"])
dΓ_Tr = Measure(Γ_Tr,degree)
# a force shall be applied on the y-direction
f_Tr(x) = VectorValue(0.0, 1e+6, 0.0)
# mass forces due to gravity, the value is set quite high, such that an impact can be seen
mass_Forces(x) = VectorValue(0.0, -1e+7, 0.0)
# Weak form
a(u,v) = ∫( ε(v) ⊙ (σ∘ε(u)) )*dΩ
l(v) = ∫( v ⋅ mass_Forces )* dΩ + ∫( v ⋅ f_Tr )* dΓ_Tr
op = AffineFEOperator(a,l,U,V0)
uh = solve(op)
writevtk(Ω,"$(output_Path)/$(output_Name)",
cellfields=[
"uh" => uh,
"epsi" => ε(uh),
"sigma" => σ∘ε(uh)])
I have a big file (75GB) memory mapped in an array d that I want to copy in another m. Because I do not have 75GB of RAM available, I did:
for (i,v) in enumerate(d)
m[i] = v
end
In order to copy the file value after value. But I get a copy rate of ~2MB/s on a SSD where I expect at least 50MB/s both in read and write.
How could I optimize this copy rate?
=== [edit] ===
According to the comments, I changed my code to the following, which sped up the write rate to 15MB/s
function copydcimg(m::Array{UInt16,4}, d::Dcimg)
m .= d
Mmap.sync!(m)
end
copydcimg(m,d)
At this point, I think I should optimize the Dcimg code. This binary file is made of frames spaced by a timestamp. Here is the code I use to access the frames:
module dcimg
using Mmap
using TOML
struct Dcimg <: AbstractArray{UInt16,4} # struct allowing to access dcimg file
filename::String # filename of the dcimg
header::Int # header size in bytes
clock::Int # clock size in bytes
x::Int
y::Int
z::Int
t::Int
m # linear memory map
Dcimg(filename, header, clock, x, y, z, t) =
new(filename, header, clock, x, y, z, t,
Mmap.mmap(open(filename), Array{UInt16, 3},
(x*y+clock÷sizeof(UInt16), z, t), header)
)
end
# following functions allows to access DCIMG like an Array
Base.size(D::Dcimg) = (D.x, D.y, D.z, D.t)
# skip clock
Base.getindex(D::Dcimg, i::Int) =
D.m[i + (i ÷ (D.x*D.y))*D.clock÷sizeof(UInt16)]
Base.getindex(D::Dcimg, x::Int, y::Int, z::Int, t::Int) =
D[x + D.x*((y-1) + D.y*((z-1) + D.z*(t-1)))]
# allowing to automatically parse size
function Dcimg(pathtag)
p = TOML.parsefile(pathtag * ".toml")
return Dcimg(pathtag * ".dcimg",
# ...
)
end
export Dcimg, getframe
end
I got it! The solution was to copy the file chunk by chunk lets say by frame (around 1024×720 UInt16). This way I reached 300MB/s, which I didn't even know was possible in single thread. Here is the code.
In module dcimg, I added the methods to access the file frame by frame
# get frame number n (starting form 1)
getframe(D::Dcimg,n::Int) =
reshape(D.m[
D.x*D.y*(n-1)+1 + (n-1)*D.clock÷sizeof(UInt16) : # cosmetic line break
D.x*D.y*n + (n-1)*D.clock÷sizeof(UInt16)
], D.x, D.y)
# get frame for layer z, time t (starting from 1)
getframe(D::Dcimg,z::Int,t::Int) =
getframe(D::Dcimg,(z-1)+D.z*(t-1))
Iterating over the frames within a loop
function copyframes(m::Array{UInt16,4}, d::Dcimg)
N = d.z*d.t
F = d.x*d.y
for i in 1:N
m[(i-1)*F+1:i*F] = getframe(d, i)
end
end
copyframes(m,d)
Thanks all in comments for leading me to this.
===== edit =====
for further reading, you might look at:
dd: How to calculate optimal blocksize?
http://blog.tdg5.com/tuning-dd-block-size/
which give hints about the optimal block size to copy at a time.
I'd like to write an iterator that behaves exactly like ipairs, except which takes a second argument. The second argument would be a table of the indices that ipairs should loop over.
I'm wondering if my current approach is inefficient, and how I could improve it with closures.
I'm also open to other methods of accomplishing the same thing. But I like iterators because they're easy to use and debug.
I'll be making references to and using some of the terminology from Programming in Lua (PiL), especially the chapter on closures (chapter 7 in the link).
So I'd like to have this,
ary = {10,20,30,40}
for i,v in selpairs(ary, {1,3}) do
ary[i] = v+5
print(string.format("ary[%d] is now = %g", i, ary[i]))
end
which would output this:
ary[1] is now = 15
ary[3] is now = 35
My current approach is this : (in order: iterator, factory, then generic for)
iter = function (t, s)
s = s + 1
local i = t.sel[s]
local v = t.ary[i]
if v then
return s, i, v
end
end
function selpairs (ary, sel)
local t = {}
t.ary = ary
t.sel = sel
return iter, t, 0
end
ary = {10,20,30,40}
for _,i,v in selpairs(ary, {1,3}) do
ary[i] = v+5
print(string.format("ary[%d] is now = %g", i, ary[i]))
end
-- same output as before
It works. sel is the array of 'selected' indices. ary is the array you want to perform the loop on. Inside iter, s indexes sel, and i indexes ary.
But there are a few glaring problems.
I must always discard the first returned argument s (_ in the for loop). I never need s, but it has to be returned as the first argument since it is the "control variable".
The "invariant state" is actually two invariant states (ary and sel) packed into a single table. Pil says that this is more expensive, and recommends using closures. (Hence my writing this question).
The rest can of this can be ignored. I'm just providing more context for what I'm wanting to use selpairs for.
I'm mostly concerned with the second problem. I'm writing this for a library I'm making for generating music. Doing simple stuff like ary[i] = v+5 won't really be a problem. But when I do stuff like accessing object properties and checking bounds, then I get concerned that the 'invariant state as a table' approach may be creating unnecessary overhead. Should I be concerned about this?
If anything, I'd like to know how to write this with closures just for the knowledge.
Of course, I've tried using closures, but I'm failing to understand the scope of "locals in enclosing functions" and how it relates to a for loop calling an iterator.
As for the first problem, I imagine I could make the control variable a table of s, i, and v. And at the return in iter, unpack the table in the desired order.
But I'm guessing that this is inefficient too.
Eventually, I'd like to write an iterator which does this, except nested into itself. My main data structure is arrays of arrays, so I'd hope to make something like this:
ary_of_arys = {
{10, 20, 30, 40},
{5, 6, 7, 8},
{0.9, 1, 1.1, 1.2},
}
for aoa,i,v in selpairs_inarrays(ary_of_arys, {1,3}, {2,3,4}) do
ary_of_arys[aoa][i] = v+5
end
And this too, could use the table approach, but it'd be nice to know how to take advantage of closures.
I've actually done something similar: A function that basically does the same thing by taking a function as it's fourth and final argument. It works just fine, but would this be less inefficient than an iterator?
You can hide "control variable" in an upvalue:
local function selpairs(ary, sel)
local s = 0
return
function()
s = s + 1
local i = sel[s]
local v = ary[i]
if v then
return i, v
end
end
end
Usage:
local ary = {10,20,30,40}
for i, v in selpairs(ary, {1,3}) do
ary[i] = v+5
print(string.format("ary[%d] is now = %g", i, ary[i]))
end
Nested usage:
local ary_of_arys = {
{10, 20, 30, 40},
{5, 6, 7, 8},
{0.9, 1, 1.1, 1.2},
}
local outer_indices = {1,3}
local inner_indices = {2,3,4}
for aoa, ary in selpairs(ary_of_arys, outer_indices) do
for i, v in selpairs(ary, inner_indices) do
ary[i] = v+5 -- This is the same as ary_of_arys[aoa][i] = v+5
end
end
Not sure if I understand what you want to achive but why not simply write
local values = {"a", "b", "c", "d"}
for i,key in ipairs {3,4,1} do
print(values[key])
end
and so forth, instead of implementing all that interator stuff? I mean your use case is rather simple. It can be easily extended to more dimensions.
And here's a co-routine based possibility:
function selpairs(t,selected)
return coroutine.wrap(function()
for _,k in ipairs(selected) do
coroutine.yield(k,t[k])
end
end)
end
I am looking for a way to find duplicate images using AutoIt. I've looked into PixelSearch and SearchImage but neither do exactly what I need them to do.
I am trying to compare 2 images by filename and see if they are the same image (a duplicate). The best way I've thought to do it would be to:
1) Get both image sizes in pixels
2) Use a while loop to get the color of each pixel and store it in an array
3) Check to see if both arrays are equal to each other.
Does anybody have any ideas on how to achieve this?
I just did some more research on this subject and built a small UDF based on a few answers I read. (Mainly based off of monoceres's answer on AutoItScript.com). I figured I would post my solution here to help any future developers!
CompareImagesUDF.au3
Func _CompareImages($ciImageOne, $ciImageTwo)
_GDIPlus_Startup()
$fname1=$ciImageOne
If $fname1="" Then Exit
$fname2=$ciImageTwo
If $fname2="" Then Exit
$bm1 = _GDIPlus_ImageLoadFromFile($fname1)
$bm2 = _GDIPlus_ImageLoadFromFile($fname2)
; MsgBox(0, "bm1==bm2", CompareBitmaps($bm1, $bm2))
Return CompareBitmaps($bm1, $bm2)
_GDIPlus_ImageDispose($bm1)
_GDIPlus_ImageDispose($bm2)
_GDIPlus_Shutdown()
EndFunc
Func CompareBitmaps($bm1, $bm2)
$Bm1W = _GDIPlus_ImageGetWidth($bm1)
$Bm1H = _GDIPlus_ImageGetHeight($bm1)
$BitmapData1 = _GDIPlus_BitmapLockBits($bm1, 0, 0, $Bm1W, $Bm1H, $GDIP_ILMREAD, $GDIP_PXF32RGB)
$Stride = DllStructGetData($BitmapData1, "Stride")
$Scan0 = DllStructGetData($BitmapData1, "Scan0")
$ptr1 = $Scan0
$size1 = ($Bm1H - 1) * $Stride + ($Bm1W - 1) * 4
$Bm2W = _GDIPlus_ImageGetWidth($bm2)
$Bm2H = _GDIPlus_ImageGetHeight($bm2)
$BitmapData2 = _GDIPlus_BitmapLockBits($bm2, 0, 0, $Bm2W, $Bm2H, $GDIP_ILMREAD, $GDIP_PXF32RGB)
$Stride = DllStructGetData($BitmapData2, "Stride")
$Scan0 = DllStructGetData($BitmapData2, "Scan0")
$ptr2 = $Scan0
$size2 = ($Bm2H - 1) * $Stride + ($Bm2W - 1) * 4
$smallest = $size1
If $size2 < $smallest Then $smallest = $size2
$call = DllCall("msvcrt.dll", "int:cdecl", "memcmp", "ptr", $ptr1, "ptr", $ptr2, "int", $smallest)
_GDIPlus_BitmapUnlockBits($bm1, $BitmapData1)
_GDIPlus_BitmapUnlockBits($bm2, $BitmapData2)
Return ($call[0]=0)
EndFunc ;==>CompareBitmaps
Now to compare imagages, all you have to do is include the CompareImagesUDF.au3 file and call the function.
CompareImagesExample.au3
#Include "CompareImagesUDF.au3"
; Define the two images (They can be different file formats)
$img1 = "Image1.jpg"
$img2 = "Image2.jpg"
; Compare the two images
$duplicateCheck = _CompareImages($img1, $img2)
MsgBox(0,"Is Duplicate?", $duplicateCheck)
If you want to find out if both images are an exact match, regardless if names are the same or different, use the built-in Crypt function _Crypt_HashFile with MD2 or MD5 to make a hash of both files and compare that.
So I have a table that holds references to other tables like:
local a = newObject()
a.collection = {}
for i = 1, 100 do
local b = newObject()
a[#a + 1] = b
end
Now if I want to see if a particular object is within "a" I have to use pairs like so:
local z = a.collection[ 99 ]
for i,j in pairs( a.collection ) do
if j == z then
return true
end
end
The z object is in the 99th spot and I would have to wait for pairs to iterate all the way throughout the other 98 objects. This set up is making my program crawl. Is there a way to make some sort of key that isn't a string or a table to table comparison that is a one liner? Like:
if a.collection[{z}] then return true end
Thanks in advance!
Why are you storing the object in the value slot and not the key slot of the table?
local a = newObject()
a.collection = {}
for i = 1, 100 do
local b = newObject()
a.collection[b] = i
end
to see if a particular object is within "a"
return a.collection[b]
If you need integer indexed access to the collection, store it both ways:
local a = newObject()
a.collection = {}
for i = 1, 100 do
local b = newObject()
a.collection[i] = b
a.collection[b] = i
end
Finding:
local z = a.collection[99]
if a.collection[z] then return true end
Don't know if it's faster or not, but maybe this helps:
Filling:
local a = {}
a.collection = {}
for i = 1, 100 do
local b = {}
a.collection[b] = true -- Table / Object as index
end
Finding:
local z = a.collection[99]
if a.collection[z] then return true end
If that's not what you wanted to do you can break your whole array into smaller buckets and use a hash to keep track which object belongs to which bucket.
you might want to consider switching from using pairs() to using a regular for loop and indexing the table, pairs() seems to be slower on larger collections of tables.
for i=1, #a.collection do
if a.collection[i] == z then
return true
end
end
i compared the speed of iterating through a collection of 1 million tables using both pairs() and table indexing, and the indexing was a little bit faster every time. try it yourself using os.clock() to profile your code.
i can't really think of a faster way of your solution other than using some kind of hashing function to set unique indexes into the a.collection table. however, doing this would make getting a specific table out a non-trivial task (you wouldn't just be able to do a.collection[99], you'd have to iterate through until you found one you wanted. but then you could easily test if the table was in a.collection by doing something like a.collection[hashFunc(z)] ~= nil...)