I can't figure out how to get my recursive call to work in Scratch. Can anyone make any suggestions?
change result by (result * number1) increases result by result * number1. You want to set result directly to result * number1, so use a set ... to ... block instead.
Related
I have a program for doing Fourier series and I wanted to switch to CuArrays to make it faster. The code is as follows (extract):
#Arrays I want to use
coord = CuArray{ComplexF64,1}(complex.(a[:,1],a[:,2]))
t=CuArray{Float64,1}(-L:(2L/(N-1)):L)
#Array of indexes in the form [0,1,-1,2,-2,...]
n=[((-1)^i)div(i,2) for i in 1:grado]
#Array of functions I need for calculations
base= [x -> exp(π * im * i * x / L) / L for i in n]
base[i](1.) #This line is OK
base[i](-1:.1:1) #This line is OK
base[i].(t) #This line gives error!
base[i].(CuArray{Float64,1}(t)) #This line gives error!
And the error is:
GPU broadcast resulted in non-concrete element type Any.
This probably means that the function you are broadcasting contains an error or type instability.
If I change it like this
base= [(x::Float64) -> (exp(π * im * i * x / L) / L)::ComplexF64 for i in n]
the same lines still give error, but the error now is:
UndefVarError: parameters not defined
Any idea how I could fix this?
Thank you in advance!
Package information:
(#v1.6) pkg> st CUDA
Status `C:\Users\marce\.julia\environments\v1.6\Project.toml`
[052768ef] CUDA v2.6.2
P.S.: This other function has the same problem:
function integra(inizio, fine, arr)
N=size(arr,1)
h=(fine-inizio)/N
integrale=sum(arr)
integrale -= (first(arr)+last(arr))/2
integrale *= h
end
L=2
integra(-L,L,coord)
The first and easier problem is that you should take care to declare global variables to be constant so that the compiler can assume a constant type: const L = 2. A mere L = 2 allows you to do something like L = SomeOtherType(), and if that type can be Anything, so must the return type of your functions. On the CPU that's only a performance hit, but it's a no-no for the GPU. If you actually want L to vary in value, pass it in as an argument so the compiler can still infer types within a function.
Your ::ComplexF64 assertion did actually force a concrete return type, though the middle of the function is still type unstable (check with #code_warntype). The second problem you ran into after that patch was probably caused by this recently patched conflict between ExprTools.jl and LLVM.jl. Seems like you just need to update the packages or maybe reinstall them.
I'm not getting the output I want. I don't understand why the result is duplicated. Can someone help me?
for $i in 1 to 2
let $rng:=random-number-generator()
let $rng1:=$rng('permute')(1 to 10)
let $rng:=$rng('next')()
let $rng2:=$rng('permute')(1 to 10)
let $rng:=$rng('next')()
let $rng3:=$rng('permute')(1 to 10)
return (string-join($rng1),string-join($rng2),string-join($rng3),",")
result:
23496815107
31018674529
31017684259
23496815107
31018674529
31017684259
The result is duplicated because of the initial for $i in 1 to 2, and because the variable $i is not actually used anywhere.
I edited the query based on your comment (getting 10 numbers). From what I understand, the difficulty here is to chain the calls (alternating between 'next' and 'permute'). Chaining calls can be done with a tail recursion.
declare function local:multiple-calls(
$rng as function(*),
$number-of-times as xs:integer) as item()* {
if($number-of-times le 0)
then ()
else
let $rng := $rng('next')
return ($rng('permute')(1 to 10),
local:multiple-calls($rng, $number-of-times - 1))
};
local:multiple-calls(random-number-generator(), 10)
Note: I am not sure if (1 to 10) is what needs to actually be passed to the call to $rng('permute'), or if it was an attempt to output ten numbers. In doubt, I haven't changed it.
The specification is here:
http://www.w3.org/TR/xpath-functions-31/#func-random-number-generator
It says:
Both forms of the function are ·deterministic·: calling the function
twice with the same arguments, within a single ·execution scope·,
produces the same results.
If you supply $i as the $seed argument to random-number-generator then the two sequences should be different.
I think I now understand what confuses you in this original query. One could indeed expect the random numbers to be generated differently for each iteration of $i.
However, XQuery is (to put it simply, with a few exceptions) deterministic. This means that the random generator probably gets initialized in each iteration with the same, default seed.
Thus, I have a second potential answer:
If you have a way to pass a different seed to $rng, you could slightly modify your initial query by constructing a seed based on $i and maybe current-dateTime() in each iteration before generating the numbers. But it will still be the same if you execute the query several times unless you involve the current date/time.
I know you can strip units from numbers in SASS when you know the unit before-hand like this:
$number: 16px;
$without-unit: 16px / 1px;
#warn $without-unit; // 16
But is it possible to strip the unit from a number without knowing what the unit is first?
#function strip-unit($number) {
// magic code here...
}
#warn strip-unit(16px); // 16
--
UPDATE: You should never actually need to use this function. Sass math is very smart about units, and I have never seen a use-case in which stripping units was a better option than simply using correct math to get what you need. See the Sass issue thread where this has been discussed at length.
It's a clever function, but if you ever feel like using it, there's probably a problem with your math. Don't fall back on this function. Fix your math instead.
--
You need to divide by 1 of the same unit. If you use unit(), you get a string instead of a number, but if you multiply by zero and add 1, you have what you need:
#function strip-units($number) {
#return $number / ($number * 0 + 1);
}
UPDATE: In the latest versions of Sass, that becomes:
#use 'sass:math';
#function strip-units($number) {
#return math.div($number, ($number * 0 + 1));
}
That works. strip-units(13.48cm) will return 13.48.
I think you'd have to add a custom Ruby function to strip the units (see the documentation on adding custom functions). It would look something like this, I think (warning, untested):
module Sass::Script::Functions
def strip_units(num)
assert_type num, :Number
Sass::Script::Number.new(num.value)
end
end
The only use case for strip units SASS function is when writing unit conversion functions. I've only found it useful for the task of converting PX to EM/REM and vice versa.
You need to divide by 1 of the same unit. If you use unit(), you get a string instead of a number, but if you multiply by zero and add 1, you have what you need - Miriam Suzanne
I believe SASS compiler treats values very similarly to what PHP interpreter does (with a warning though), so I believe the statement above is incorrect. If you divide or multiply a string (which starts with a number e.g. '16px') with a number value (or a string value that starts with a number), the string is converted to number for the compiler to be able to perform the operation.
Same goes for adding a string to number, it converts the number to a string.
The following solution applies this tactic correctly:
#function strip-unit($value) {
#return $value / 1;
}
I am playing around with the idea of CoVectors in Julia and am getting some behaviour I didn't expect from the parser/compiler. I have defined a new CoVector type that is the ctranspose of any vector, and is just a simple decoration:
type CoVector{T<:AbstractVector}
v::T
end
They can be created (and uncreated) with ' using ctranspose:
import Base.ctranspose
function CoVector(T::DataType,d::Integer=0)
return CoVector(Array(T,d))
end
function Base.ctranspose(cv::CoVector)
return cv.v
end
function Base.ctranspose(v::AbstractVector)
return CoVector(v)
end
function Base.ctranspose(v::Vector) # this is already specialized in Base
return CoVector(v)
end
Next I want to define a simple dot product
function *(x::CoVector,y::AbstractVector)
return dot(x.v,y)
end
Which can work fine for:
v = [1,2,3]
cv = v'
cv*v
returns 14, and cv is a CoVector. But if I do
(v') * v
I get something different! In this case it is a single element array containing 14. How come parenthesis doesn't work how I expect?
In the end we see the expression gets expanded to Ac_mul_B which defaults to [dot(A,B)] and it seems that this interpretation is defined at the "operator" level.
Is this expected behaviour? Can Julia completely ignore my bracketing and change the expression as it wants? In Julia I like that I can override things in Base but is it also possible to make self-consistent changes to how operators are applied? I see the expression doesn't have head call but Symbol call... does this change in Julia 0.4? (I read somewhere that call is becoming more universal).
I guess I can fix the problem by redefining Ac_mul_B but I was very surprised that it was called at all, given my above definitions.
I'm trying to make a wrapper for some C-based sparse-matrix-handling code (see previous question). In order to call the workhorse C function, I need to create a structure that looks like this:
struct smat {
long rows;
long cols;
long vals; /* Total non-zero entries. */
long *pointr; /* For each col (plus 1), index of first non-zero entry. */
long *rowind; /* For each nz entry, the row index. */
double *value; /* For each nz entry, the value. */
};
These correspond nicely to the slots in a dgCMatrix sparse matrix. So ideally I'd just point to the internal arrays in the dgCMatrix (after verifying that the C function won't twiddle with the data [which I haven't done yet]).
For *value, it looks like I'll be able to use REALSXP or something to get a double[] as desired. But for *pointr and *rowind, I'm not sure the best way to get at an appropriate array. Will I need to loop through the entries and copy them to new arrays, casting as I go? Or can Rcpp provide some sugar here? This is the first time I've really used Rcpp much and I'm not well-versed in it yet.
Thanks.
Edit: I'm also having some linking trouble that I don't understand:
Error in dyn.load(libLFile) :
unable to load shared object '/var/folders/TL/TL+wXnanH5uhWm4RtUrrjE+++TM/-Tmp-//RtmpAA9upc/file2d4606aa.so':
dlopen(/var/folders/TL/TL+wXnanH5uhWm4RtUrrjE+++TM/-Tmp-//RtmpAA9upc/file2d4606aa.so, 6): Symbol not found: __Z8svdLAS2AP4smatl
Referenced from: /var/folders/TL/TL+wXnanH5uhWm4RtUrrjE+++TM/-Tmp-//RtmpAA9upc/file2d4606aa.so
Expected in: flat namespace
in /var/folders/TL/TL+wXnanH5uhWm4RtUrrjE+++TM/-Tmp-//RtmpAA9upc/file2d4606aa.so
Do I need to be creating my library with some special compilation flags?
Edit 2: it looks like my libargs parameter has no effect, so libsvd symbols never make it into the library. I can find no way to include libraries using cxxfunction() - here's what I'd tried, but the extra parameters (wishful-thinkingly-borrowed from cfunction()) are silently gobbled up:
fn <- cxxfunction(sig=c(nrow="integer", mi="long", mp="long", mx="numeric"),
body=code,
includes="#include <svdlib.h>\n",
cppargs="-I/Users/u0048513/Downloads/SVDLIBC",
libargs="-L/Users/u0048513/Downloads/SVDLIBC -lsvd",
plugin="Rcpp",
verbose=TRUE)
I feel like I'm going about this whole process wrong, since nothing's working. Anyone kick me in the right direction?
I decided to also post a query on the Rcpp-devel mailing list, and got some good advice & help from Dirk and Doug:
http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2011-February/001851.html
I'm still not super-facile with this stuff, but getting there. =)
I've done something similar for a [R]-Smalltalk-interface last year and went about it more generic to be able to pass all data back-and-forth by using byte-arrays:
In C i have:
DLLIMPORT void getLengthOfNextMessage(byte* a);
DLLIMPORT void getNextMessage(byte* a);
In R:
getLengthOfNextMessage <- function() {
tmp1 <- as.raw(rep(0,4))
tmp2<-.C("getLengthOfNextMessage", tmp1)
return(bvToInt(tmp2))
}
receiveMessage <- function() {
#if(getNumberOfMessages()==0) {
# print("error: no messages")
# return();
#}
tmp1<-as.raw(rep(0, getLengthOfNextMessage()+getSizeOfMessages()))
tmp2<-.C("getNextMessage", tmp1)
msg<-as.raw(tmp2[[1]])
print(":::confirm received")
print(bvToInt(msg[13:16]))
# confirmReceived(bvToInt(msg[13:16]))
return(msg)
}
I have commented-out the use of the functions getNumberOfMessages() and confirmReceived() which are specific to the problem i had to solve (multiple back-and-forth communication). Essentially, the code uses the argument byte-array to transfer the information, first the 4-byte-long length-info, then the actual data. This seems less elegant (even to me) than to use structs, but i found it to be more generic and i can hook into any dll, transfering any datatype.