I want to create a define constant that is assigned to one of multiple otherdefine constants that has the largest value. Something like:
`define MAXWIDTH $MAX(`WIDTH0,`WIDTH1,`WIDTH2)
Is this possible in Verilog/SystemVerilog?
Depending on exactly what you need, there are a few ways to do it (there is no builtin call for maximum like in other languages):
You have some vectors and you need to get the maximum width for a new vector
$bits(v1 + v2 + v3 ...)
Use the language to your advantage, noting that the addition of vectors results in a vector that has the maximum width of all the operand vector widths and use $bits to get that size. Example:
logic [1:0] x;
logic [7:0] y;
logic [10:6] z;
...
max = $bits(x + y + z); // Result: max = 8
You have a few numbers of which you need the maximum
If you put your numbers in an array or queue, you can use the max method to get the largest:
int x[] = '{n1, n2, n3, ...};
...
max = x.max;
Note that this approach has the downside that it cannot be used at compile time for getting the maximum size. Example:
int _nums[] = '{13, 2, 17, 8, -1};
...
max = _nums.max; // Result: max = 17
Basically any other time
You'll just have to use the conditional operator, either in a macro or using let:
`define max2(v1, v2) ((v1) > (v2) ? (v1) : (v2))
`define max3(v1, v2, v3) `max2((v1), `max2((v2), (v3)))
OR
let max2(v1, v2) = (v1 > v2) ? v1 : v2;
let max3(v1, v2, v3) = max2(v1, max2(v2, v3));
The advantage of macros is that you can use them as compile-time constants in a wider range of tools, while older tools might not support let as a compile-time constant (or at all). Example:
max = `max3(10, 2, 3); // Result: max = 10
OR
max = max3(10, 2, 3); // Result: max = 10
It seems that the sugar Rcpp function setdiff orders the values, which is different from the standard R function setdiff.
As an example, consider the following code:
src <-
"IntegerVector setdiff_Rcpp(IntegerVector x, IntegerVector y){
IntegerVector d = setdiff(x,y);
return(d);
}"
Rcpp::cppFunction(src)
setdiff(15:11, c(13,12))
# [1] 15 14 11
setdiff_Rcpp(15:11, c(13,12))
# [1] 11 14 15
Is it possible to obtain a result as in the standard R function?
[Edit]
I was able to solve my problem. Here is the Rcpp function I used:
// [[Rcpp::export]]
IntegerVector setdiff_R(IntegerVector x, IntegerVector y)
{
// difference of sets x & y (without reordering)
x = x[duplicated(x) == 0]; x = na_omit(x);
y = y[duplicated(y) == 0]; y = na_omit(y);
IntegerVector out(0, NA_INTEGER);
for(int i=0; i < x.length(); i++)
{
if(is_false(any(x[i] == y)))
out.push_back(x[i]);
}
return(out);
}
It only works for IntegerVector type and probably it is not optimised but it gets the job done.
I am having trouble configuring ICP in PCL 1.6(I use Android) and I believe that is the cause of an incorrect transformation matrix. What I've tried so far is this;
Downsample the point clouds I use in ICP with the following code:
pcl::VoxelGrid <pcl::PointXYZ> grid;
grid.setLeafSize(6, 6, 6);
grid.setInputCloud(output);
grid.filter(*tgt);
grid.setInputCloud(cloud_src);
grid.filter(*src);
Try to align the two point clouds with the following code :
pcl::IterativeClosestPoint<pcl::PointXYZ, pcl::PointXYZ> icp;
icp.setInputCloud(tgt);
icp.setInputTarget(src);
pcl::PointCloud<pcl::PointXYZ> Final;
pcl::PointCloud<pcl::PointXYZ> transformedCloud;
icp.setMaxCorrespondenceDistance(0.08);
icp.setMaximumIterations(500);
//icp.setTransformationEpsilon (0.000000000000000000001);
icp.setTransformationEpsilon(1e-12);
icp.setEuclideanFitnessEpsilon(1e-12);
icp.setRANSACIterations(2000);
icp.setRANSACOutlierRejectionThreshold(0.6);
I have tried all kinds of values in the options of ICP but with no success.
The code I use to create the point cloud:
int density = 1;
for (int y = 0; y < depthFrame.getHeight(); y = y + density) {
for (int x = 0; x < depthFrame.getWidth(); x = x + density) {
short z = pDepthRow[y * depthVideoMode.getResolutionX() + x];
if (z > 0 && z < depthStream.getMaxPixelValue()) {
cloud_src->points[counter].x = x;
cloud_src->points[counter].y = y;
cloud_src->points[counter].z = z;
}
}
}
Any chance somebody can help me out configuring ICP?
From what I know, PCL uses meters as a unit of measurement. so, is it intended that leaf size for downsampling is 6*6*6 !? I think it's huge !!
Try with some lower values and if it didn't work either, try ICP with the most simple configuration as follows :
pcl::IterativeClosestPoint<pcl::PointXYZ, pcl::PointXYZ> icp;
icp.setInputCloud(tgt);
icp.setInputTarget(src);
pcl::PointCloud<pcl::PointXYZ> Final;
icp.align(Final);
once, you got this working (and it should be), then start tuning the other parameters and it shouldn't be that hard to do.
Hope that helps, Cheers!
Will somebody please explain why the initial conditions are properly taken care of in the following openmodelica model compiled and simulated in OMEdit v1.9.1 beta2 in Windows, but if line 5 is commentd and 6 uncommented (x,y) is initialized to (0.5,0)?
Thank you.
class Pendulum "Planar Pendulum"
constant Real PI = 3.141592653589793;
parameter Real m = 1,g = 9.81,L = 0.5;
Real F "Force of the Rod";
output Real x(start=L*sin(PI/4)) ,y(start=-0.35355);
//output Real x(start = L * sin(PI / 4)), y(start=-L*sin(PI/4));
output Real vx,vy;
equation
m * der(vx) = -x / L * F;
m * der(vy) = (-y / L * F) - m * g;
der(x) = vx;
der(y) = vy;
x ^ 2 + y ^ 2 = L ^ 2;
end Pendulum;
The short answer is that initial values are treated merely as hints, you have to add the fixed=true attribute to force them as in:
output Real x(start=L*cos(PI/4),fixed=true);
If initialized variables are constrained, the fixed attribute should not be used on all initialized variables but on a 'proper' subset, in this case on just one.
The long answer can be found here
Does anyone know of a truly declarative language? The behavior I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself)
The behavior I'm looking for is best shown with this pseudo code:
X = 10 // define and assign two variables
Y = 20;
Z = X + Y // declare a formula that uses these two variables
X = 50 // change one of the input variables
?Z // asking for Z should now give 70 (50 + 20)
I've tried this in a lot of languages like F#, python, matlab etc, but every time I tried this they come up with 30 instead of 70. Which is correct from an imperative point of view, but I'm looking for a more declarative behavior if you know what I mean.
And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically.
The code below would obviously work in C# but it's just so much code for the job, I'm looking for something a bit more to the point without all that 'technical noise'
class BlaBla{
public int X {get;set;} // this used to be even worse before 3.0
public int Y {get;set;}
public int Z {get{return X + Y;}}
}
static void main(){
BlaBla bla = new BlaBla();
bla.X = 10;
bla.Y = 20;
// can't define anything here
bla.X = 50; // bit pointless here but I'll do it anyway.
Console.Writeline(bla.Z);// 70, hurray!
}
This just seems like so much code, curly braces and semicolons that add nothing.
Is there a language/ application (apart from Excel) that does this? Maybe I'm no doing it right in the mentioned languages, or I've completely missed an app that does just this.
I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time.
Any Constraint Programming system will do that for you.
Examples of CP systems that have an associated language are ECLiPSe, SICSTUS Prolog / CP package, Comet, MiniZinc, ...
It looks like you just want to make Z store a function instead of a value. In C#:
var X = 10; // define and assign two variables
var Y = 20;
Func<int> Z = () => X + Y; // declare a formula that uses these two variables
Console.WriteLine(Z());
X = 50; // change one of the input variables
Console.WriteLine(Z());
So the equivalent of your ?-prefix syntax is a ()-suffix, but otherwise it's identical. A lambda is a "formula" in your terminology.
Behind the scenes, the C# compiler builds almost exactly what you presented in your C# conceptual example: it makes X into a field in a compiler-generated class, and allocates an instance of that class when the code block is entered. So congratulations, you have re-discovered lambdas! :)
In Mathematica, you can do this:
x = 10; (* # assign 30 to the variable x *)
y = 20; (* # assign 20 to the variable y *)
z := x + y; (* # assign the expression x+y to the variable z *)
Print[z];
(* # prints 30 *)
x = 50;
Print[z];
(* # prints 70 *)
The operator := (SetDelayed) is different from = (Set). The former binds an unevaluated expression to a variable, the latter binds an evaluated expression.
Wanting to have two definitions of X is inherently imperative. In a truly declarative language you have a single definition of a variable in a single scope. The behavior you want from Excel corresponds to editing the program.
Have you seen Resolver One? It's like Excel with a real programming language behind it.
Here is Daniel's example in Python, since I noticed you said you tried it in Python.
x = 10
y = 10
z = lambda: x + y
# Output: 20
print z()
x = 20
# Output: 30
print z()
Two things you can look at are the cells lisp library, and the Modelica dynamic modelling language, both of which have relation/equation capabilities.
There is a Lisp library with this sort of behaviour:
http://common-lisp.net/project/cells/
JavaFX will do that for you if you use bind instead of = for Z
react is an OCaml frp library. Contrary to naive emulations with closures it will recalculate values only when needed
Objective Caml version 3.11.2
# #use "topfind";;
# #require "react";;
# open React;;
# let (x,setx) = S.create 10;;
val x : int React.signal = <abstr>
val setx : int -> unit = <fun>
# let (y,sety) = S.create 20;;
val y : int React.signal = <abstr>
val sety : int -> unit = <fun>
# let z = S.Int.(+) x y;;
val z : int React.signal = <abstr>
# S.value z;;
- : int = 30
# setx 50;;
- : unit = ()
# S.value z;;
- : int = 70
You can do this in Tcl, somewhat. In tcl you can set a trace on a variable such that whenever it is accessed a procedure can be invoked. That procedure can recalculate the value on the fly.
Following is a working example that does more or less what you ask:
proc main {} {
set x 10
set y 20
define z {$x + $y}
puts "z (x=$x): $z"
set x 50
puts "z (x=$x): $z"
}
proc define {name formula} {
global cache
set cache($name) $formula
uplevel trace add variable $name read compute
}
proc compute {name _ op} {
global cache
upvar $name var
if {[info exists cache($name)]} {
set expr $cache($name)
} else {
set expr $var
}
set var [uplevel expr $expr]
}
main
Groovy and the magic of closures.
def (x, y) = [ 10, 20 ]
def z = { x + y }
assert 30 == z()
x = 50
assert 70 == z()
def f = { n -> n + 1 } // define another closure
def g = { x + f(x) } // ref that closure in another
assert 101 == g() // x=50, x + (x + 1)
f = { n -> n + 5 } // redefine f()
assert 105 == g() // x=50, x + (x + 5)
It's possible to add automagic memoization to functions too but it's a lot more complex than just one or two lines. http://blog.dinkla.net/?p=10
In F#, a little verbosily:
let x = ref 10
let y = ref 20
let z () = !x + !y
z();;
y <- 40
z();;
You can mimic it in Ruby:
x = 10
y = 20
z = lambda { x + y }
z.call # => 30
z = 50
z.call # => 70
Not quite the same as what you want, but pretty close.
not sure how well metapost (1) would work for your application, but it is declarative.
Lua 5.1.4 Copyright (C) 1994-2008 Lua.org, PUC-Rio
x = 10
y = 20
z = function() return x + y; end
x = 50
= z()
70
It's not what you're looking for, but Hardware Description Languages are, by definition, "declarative".
This F# code should do the trick. You can use lazy evaluation (System.Lazy object) to ensure your expression will be evaluated when actually needed, not sooner.
let mutable x = 10;
let y = 20;
let z = lazy (x + y);
x <- 30;
printf "%d" z.Value