Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 14:14:23 UTC, Seb wrote: ``` T[] a = slice.ptr[0.. slice.elementsCount]; ``` This would work only for slices with continuous memory representation and positive strides. -- Ilya
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 14:14:23 UTC, Seb wrote: On Wednesday, 15 June 2016 at 13:13:05 UTC, data pulverizer And where can I find more cool tricks like that? Browse the source code and the unittests. Phobos is an amazing resource :) Very true! That's great many thanks!
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 13:13:05 UTC, data pulverizer wrote:
On Wednesday, 15 June 2016 at 12:10:32 UTC, Seb wrote:
As said you can avoid the copy (see below). I also profiled it
a bit and it was interesting to see that 50% of the runtime
are spent on generating the random matrix. On my machine now
both scripts take 1.5s when compiled with
I didn't benchmark the RNG but I did notice it took a lot of
time to generate the matrix but for now I am focused on the
BLAS side of things.
I am puzzled about how your code works:
Firstly:
I didn't know that you could substitute an array for its first
element in D though I am aware that a pointer to an array's
first element is equivalent to passing the array in C.
auto matrix_mult(T)(T[] A, T[] B, Slice!(2, T*) a, Slice!(2,
T*) b){
...
gemm(Order.ColMajor, Transpose.NoTrans, Transpose.NoTrans,
M, N, K, 1., A.ptr, K, B.ptr, N, 0, C.ptr, N);
return C.sliced(M, N);
}
You wrote that too :-)
For more infos see:
https://dlang.org/spec/arrays.html
However that's very dangerous, so use just slices wherever you
can.
Secondly:
I am especially puzzled about using the second element to stand
in for the slice itself. How does that work? And where can I
find more cool tricks like that?
void main()
{
...
auto C = matrix_mult(ta[0], tb[0], ta[1], tb[1]);
sw.stop();
writeln("Time taken: \n\t", sw.peek().msecs, " [ms]");
}
Many thanks!
Btw you don't even need to save tuples, the pointer is already
saved in the slice ;-)
N.b: afaik you need the latest version of mir, because
std.experimental.ndslice in 2.071 doesn't expose the `.ptr` (yet).
// Random matrix
auto rmat(T)(ulong nrow, ulong ncol, T min, T max){
return runif(nrow*ncol, min, max).sliced(nrow, ncol);
}
auto matrix_mult(T)(Slice!(2, T*) a, Slice!(2, T*) b){
int M = to!int(a.shape[0]);
int K = to!int(a.shape[1]);
int N = to!int(b.shape[1]);
int n_el = to!int(a.elementsCount);
T[] C = new T[M*N];
gemm(Order.ColMajor, Transpose.NoTrans, Transpose.NoTrans, M,
N, K, 1., a.ptr, K, b.ptr, N, 0, C.ptr, N);
return C.sliced(M, N);
}
void main()
{
int n = 4000;
auto A = rmat(n, n, 0., 1.);
auto B = rmat(n, n, 0., 1. );
StopWatch sw;
sw.start();
auto C = matrix_mult(A, B);
sw.stop();
writeln("Time taken: \n\t", sw.peek().msecs, " [ms]");
}
If you really want to get the original T[] back, you could use
something like
```
T[] a = slice.ptr[0.. slice.elementsCount];
```
but for most cases `byElement` would be a lot better, because all
transformations etc are of course only applied to your view.
And where can I find more cool tricks like that?
Browse the source code and the unittests. Phobos is an amazing
resource :)
Re: ndslice: convert a sliced object to T[]
Oh, I didn't see that runif now returns a tuple.
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 12:10:32 UTC, Seb wrote:
As said you can avoid the copy (see below). I also profiled it
a bit and it was interesting to see that 50% of the runtime are
spent on generating the random matrix. On my machine now both
scripts take 1.5s when compiled with
I didn't benchmark the RNG but I did notice it took a lot of time
to generate the matrix but for now I am focused on the BLAS side
of things.
I am puzzled about how your code works:
Firstly:
I didn't know that you could substitute an array for its first
element in D though I am aware that a pointer to an array's first
element is equivalent to passing the array in C.
auto matrix_mult(T)(T[] A, T[] B, Slice!(2, T*) a, Slice!(2,
T*) b){
...
gemm(Order.ColMajor, Transpose.NoTrans, Transpose.NoTrans,
M, N, K, 1., A.ptr, K, B.ptr, N, 0, C.ptr, N);
return C.sliced(M, N);
}
Secondly:
I am especially puzzled about using the second element to stand
in for the slice itself. How does that work? And where can I find
more cool tricks like that?
void main()
{
...
auto C = matrix_mult(ta[0], tb[0], ta[1], tb[1]);
sw.stop();
writeln("Time taken: \n\t", sw.peek().msecs, " [ms]");
}
Many thanks!
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 11:19:20 UTC, data pulverizer wrote:
On Wednesday, 15 June 2016 at 09:32:21 UTC, Andrea Fontana
wrote:
Then I think the slice.byElement.array is the right solution.
The problem with that is that it slows down the code. I
compared matrix multiplication between R and D's cblas adaptor
and ndslice.
n = 4000
Matrices: A, B
Sizes: both n by n
Engine: both call openblas
R Elapsed Time: 2.709 s
D's cblas and ndslice: 3.593 s
The R code:
n = 4000; A = matrix(runif(n*n), nr = n); B =
matrix(runif(n*n), nr = n)
system.time(C <- A%*%B)
The D code:
import std.stdio : writeln;
import std.experimental.ndslice;
import std.random : Random, uniform;
import std.conv : to;
import std.array : array;
import cblas;
import std.datetime : StopWatch;
T[] runif(T)(ulong len, T min, T max){
T[] arr = new T[len];
Random gen;
for(ulong i = 0; i < len; ++i)
arr[i] = uniform(min, max, gen);
return arr;
}
// Random matrix
auto rmat(T)(ulong nrow, ulong ncol, T min, T max){
return runif(nrow*ncol, min, max).sliced(nrow, ncol);
}
auto matrix_mult(T)(Slice!(2, T*) a, Slice!(2, T*) b){
int M = to!int(a.shape[0]);
int K = to!int(a.shape[1]);
int N = to!int(b.shape[1]);
int n_el = to!int(a.elementsCount);
T[] A = a.byElement.array;
T[] B = b.byElement.array;
T[] C = new T[M*N];
gemm(Order.ColMajor, Transpose.NoTrans, Transpose.NoTrans, M,
N, K, 1., A.ptr, K, B.ptr, N, 0, C.ptr, N);
return C.sliced(M, N);
}
void main()
{
int n = 4000;
auto A = rmat(n, n, 0., 1.);
auto B = rmat(n, n, 0., 1. );
StopWatch sw;
sw.start();
auto C = matrix_mult(A, B);
sw.stop();
writeln("Time taken: \n\t", sw.peek().msecs, " [ms]");
}
In my system monitor I can see the copy phase in the D process
as as single core process. There should be a way to do go from
ndslice to T[] without copying. Using a foreach loop is even
slower
As said you can avoid the copy (see below). I also profiled it a
bit and it was interesting to see that 50% of the runtime are
spent on generating the random matrix. On my machine now both
scripts take 1.5s when compiled with
DFLAGS="-release -O3 -boundscheck=off" dub foo2.d --compiler=ldc
(`-b release` would also work)
#!/usr/bin/env dub
/+ dub.sdl:
name "matrix_mult"
dependency "cblas" version="~master"
dependency "mir" version="~>0.15"
+/
import std.stdio : writeln;
import mir.ndslice;
import std.random : Random, uniform;
import std.conv : to;
import std.array : array;
import cblas;
import std.datetime : StopWatch;
T[] runif(T)(ulong len, T min, T max){
T[] arr = new T[len];
Random gen;
for(ulong i = 0; i < len; ++i)
arr[i] = uniform(min, max, gen);
return arr;
}
// Random matrix
auto rmat(T)(ulong nrow, ulong ncol, T min, T max){
import std.typecons : tuple;
auto arr = runif(nrow*ncol, min, max);
return tuple(arr, arr.sliced(nrow, ncol));
}
auto matrix_mult(T)(T[] A, T[] B, Slice!(2, T*) a, Slice!(2, T*)
b){
int M = to!int(a.shape[0]);
int K = to!int(a.shape[1]);
int N = to!int(b.shape[1]);
int n_el = to!int(a.elementsCount);
T[] C = new T[M*N];
gemm(Order.ColMajor, Transpose.NoTrans, Transpose.NoTrans, M,
N, K, 1., A.ptr, K, B.ptr, N, 0, C.ptr, N);
return C.sliced(M, N);
}
void main()
{
int n = 4000;
auto ta = rmat(n, n, 0., 1.);
auto tb = rmat(n, n, 0., 1. );
StopWatch sw;
sw.start();
auto C = matrix_mult(ta[0], tb[0], ta[1], tb[1]);
sw.stop();
writeln("Time taken: \n\t", sw.peek().msecs, " [ms]");
}
For performance issues, you should definitely open an issue at
mir (the development library of ndslice):
https://github.com/libmir/mir
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 09:32:21 UTC, Andrea Fontana wrote:
Then I think the slice.byElement.array is the right solution.
The problem with that is that it slows down the code. I compared
matrix multiplication between R and D's cblas adaptor and ndslice.
n = 4000
Matrices: A, B
Sizes: both n by n
Engine: both call openblas
R Elapsed Time: 2.709 s
D's cblas and ndslice: 3.593 s
The R code:
n = 4000; A = matrix(runif(n*n), nr = n); B = matrix(runif(n*n),
nr = n)
system.time(C <- A%*%B)
The D code:
import std.stdio : writeln;
import std.experimental.ndslice;
import std.random : Random, uniform;
import std.conv : to;
import std.array : array;
import cblas;
import std.datetime : StopWatch;
T[] runif(T)(ulong len, T min, T max){
T[] arr = new T[len];
Random gen;
for(ulong i = 0; i < len; ++i)
arr[i] = uniform(min, max, gen);
return arr;
}
// Random matrix
auto rmat(T)(ulong nrow, ulong ncol, T min, T max){
return runif(nrow*ncol, min, max).sliced(nrow, ncol);
}
auto matrix_mult(T)(Slice!(2, T*) a, Slice!(2, T*) b){
int M = to!int(a.shape[0]);
int K = to!int(a.shape[1]);
int N = to!int(b.shape[1]);
int n_el = to!int(a.elementsCount);
T[] A = a.byElement.array;
T[] B = b.byElement.array;
T[] C = new T[M*N];
gemm(Order.ColMajor, Transpose.NoTrans, Transpose.NoTrans, M, N,
K, 1., A.ptr, K, B.ptr, N, 0, C.ptr, N);
return C.sliced(M, N);
}
void main()
{
int n = 4000;
auto A = rmat(n, n, 0., 1.);
auto B = rmat(n, n, 0., 1. );
StopWatch sw;
sw.start();
auto C = matrix_mult(A, B);
sw.stop();
writeln("Time taken: \n\t", sw.peek().msecs, " [ms]");
}
In my system monitor I can see the copy phase in the D process as
as single core process. There should be a way to do go from
ndslice to T[] without copying. Using a foreach loop is even
slower
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 08:56:15 UTC, data pulverizer wrote: On Wednesday, 15 June 2016 at 08:53:22 UTC, Andrea Fontana wrote: On Wednesday, 15 June 2016 at 08:25:35 UTC, data pulverizer wrote: I guess foreach would not copy the elements? for example: foreach(el; slice.byElement) x ~= el; But it feels wrong to be doing work pulling elements that already exists by using foreach. I feel as if I am missing something obvious but can't get it. The question is: why you need to put them inside an array? If you can, leave them in the lazy range and work on it. I need this to work with external libraries that only deal with one dimensional arrays. Then I think the slice.byElement.array is the right solution.
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 08:53:22 UTC, Andrea Fontana wrote: On Wednesday, 15 June 2016 at 08:25:35 UTC, data pulverizer wrote: I guess foreach would not copy the elements? for example: foreach(el; slice.byElement) x ~= el; But it feels wrong to be doing work pulling elements that already exists by using foreach. I feel as if I am missing something obvious but can't get it. The question is: why you need to put them inside an array? If you can, leave them in the lazy range and work on it. I need this to work with external libraries that only deal with one dimensional arrays.
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 08:25:35 UTC, data pulverizer wrote: I guess foreach would not copy the elements? for example: foreach(el; slice.byElement) x ~= el; But it feels wrong to be doing work pulling elements that already exists by using foreach. I feel as if I am missing something obvious but can't get it. The question is: why you need to put them inside an array? If you can, leave them in the lazy range and work on it.
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 07:45:12 UTC, Andrea Fontana wrote: On Wednesday, 15 June 2016 at 07:24:23 UTC, data pulverizer wrote: On Wednesday, 15 June 2016 at 03:17:39 UTC, Seb wrote: On Wednesday, 15 June 2016 at 03:11:23 UTC, data pulverizer wrote: in that case: import std.array : array; int[] x = slice.byElement.array; Are you sure you want to create a _copy_ of your data? In most cases you don't need that ;-) thanks, now I can go to bed! You are welcome. Sleep tight! Thanks, I did. I definitely don't want to create a copy! I thought .byElement would provide a range which I assume is a reference am I forcing it to copy by using .array? Yes. You're forcing it to read all elements and copy them in a new array. I guess foreach would not copy the elements? for example: foreach(el; slice.byElement) x ~= el; But it feels wrong to be doing work pulling elements that already exists by using foreach. I feel as if I am missing something obvious but can't get it.
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 07:24:23 UTC, data pulverizer wrote: On Wednesday, 15 June 2016 at 03:17:39 UTC, Seb wrote: On Wednesday, 15 June 2016 at 03:11:23 UTC, data pulverizer wrote: in that case: import std.array : array; int[] x = slice.byElement.array; Are you sure you want to create a _copy_ of your data? In most cases you don't need that ;-) thanks, now I can go to bed! You are welcome. Sleep tight! Thanks, I did. I definitely don't want to create a copy! I thought .byElement would provide a range which I assume is a reference am I forcing it to copy by using .array? Yes. You're forcing it to read all elements and copy them in a new array.
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 03:17:39 UTC, Seb wrote: On Wednesday, 15 June 2016 at 03:11:23 UTC, data pulverizer wrote: in that case: import std.array : array; int[] x = slice.byElement.array; Are you sure you want to create a _copy_ of your data? In most cases you don't need that ;-) thanks, now I can go to bed! You are welcome. Sleep tight! Thanks, I did. I definitely don't want to create a copy! I thought .byElement would provide a range which I assume is a reference am I forcing it to copy by using .array?
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 03:11:23 UTC, data pulverizer wrote: in that case: import std.array : array; int[] x = slice.byElement.array; Are you sure you want to create a _copy_ of your data? In most cases you don't need that ;-) thanks, now I can go to bed! You are welcome. Sleep tight!
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 02:50:30 UTC, Seb wrote: On Wednesday, 15 June 2016 at 02:43:37 UTC, data pulverizer wrote: How do I unravel a sliced item T[].sliced(...) to an array T[]? For instance: import std.experimental.ndslice; auto slice = new int[12].sliced(3, 4); int[] x = ??; Thanks A slice is just a _view_ on your memory, the easiest way is to save a reference to your array like this: ``` int[] arr = new int[12]; auto slice = arr.sliced(3, 4); slice[1, 1] = 42; arr // [0, 0, 0, 0, 0, 42, 0, 0, 0, 0, 0, 0] ``` For a general case, you should give `byElement` a try: https://dlang.org/phobos/std_experimental_ndslice_selection.html#byElement in that case: import std.array : array; int[] x = slice.byElement.array; thanks, now I can go to bed!
Re: ndslice: convert a sliced object to T[]
On Wednesday, 15 June 2016 at 02:43:37 UTC, data pulverizer wrote: How do I unravel a sliced item T[].sliced(...) to an array T[]? For instance: import std.experimental.ndslice; auto slice = new int[12].sliced(3, 4); int[] x = ??; Thanks A slice is just a _view_ on your memory, the easiest way is to save a reference to your array like this: ``` int[] arr = new int[12]; auto slice = arr.sliced(3, 4); slice[1, 1] = 42; arr // [0, 0, 0, 0, 0, 42, 0, 0, 0, 0, 0, 0] ``` For a general case, you should give `byElement` a try: https://dlang.org/phobos/std_experimental_ndslice_selection.html#byElement
