Questions tagged [packed-arrays]
Tag for questions about packed arrays. Packed Arrays are data structures that can be seen as monolithic blocks containing a single data type, particularly Integers and Reals. Many functions operate very efficient on packed arrays. Questions may deal with packed array generation, conversion, and usage.
74
questions
13
votes
1
answer
299
views
How to convert the ListVector into PackedArray in FunctionCompile
Cross post here
I have a compile function cf to calculate the mean for a ragged list:
...
- 26.1k
0
votes
0
answers
69
views
Packed/Unpacked array - what object/like 0 or 1?/how to check/ [duplicate]
In Mathematica, there is a concept called packed array.
...
- 4,037
2
votes
1
answer
65
views
What circumstances would cause memory to inflate while packing the sublists of a ragged matrix?
I'm working with a ragged matrix of considerable size (ByteCount = 47749114088; Length = 563529128). I had seen a suggestion mentioned in other questions (here on StackExchange), that one might be ...
- 2,104
3
votes
0
answers
68
views
Fixing a step size with a variable causes array to be unpacked?
I would expect the following code to produce a packed 11x11x11 element array of 64 bit integers, but it doesn't:
...
- 455
6
votes
1
answer
74
views
Unexpected unpacking of wrapped PackedArray
I'm confused as to why the following leads to unpacking of a PackedArray:
...
- 3,140
5
votes
1
answer
57
views
Why is extracting values from an Association with 1 level slower than extracting values from a list of depth 1?
I am not looking for a solution or work-around, but an explanation.
Here are six examples of doing a trivial operation on an association and a list.
Initially, I was curious about the cost of calling ...
- 3,916
1
vote
0
answers
82
views
5
votes
2
answers
149
views
Unexpected timing result of Total and Part performance of packed array
Define
a = RandomReal[1., {2, 100, 100, 100}];
then
Total[a, Infinity]; // RepeatedTiming
{0.00183727, Null}
and
...
- 16.9k
2
votes
1
answer
39
views
Compression results in unpacking of integers but not reals
Consider the following;
Pack some integers.
In[287]:= Clear[p5i, p5ic, p5icu, p5r, p5rc, p5rcu]
In[288]:= p5i = ToPackedArray@Range@5
Out[288]= {1, 2, 3, 4, 5}
...
- 790
1
vote
0
answers
36
views
spontaneously quitting kernel, assignment and packed arrays
I am having an issue where the kernel spontaneously quits, deep in a long code that I have used for quite some time without this issue.
I've tracked it down to an assignment of the form:
a[[All, All, ...
- 1,223
4
votes
1
answer
62
views
Can't initialise packed array of rational numbers [closed]
If I evaluate the following code
t = Developer`ToPackedArray[{0, 2/7, -(1/7)}];
Developer`PackedArrayQ[t]
Mathematica returns ...
- 1,460
6
votes
1
answer
137
views
Why Does Subsets[...,{n}] not Output a Packed List, Even Though it Doesn't Unpack?
Assume list is packed.
I expect Subsets[] is a structural operation because it depends on the number of elements, not on what ...
- 1,597
1
vote
1
answer
85
views
Excessive usage of memory while using ArrayFlatten or Flatten
I have 16 NxN matrices, where N can be anywhere between 1000-64000.. Some of them are real and some of them are complex. I want to Reshape then to form a 4Nx4N matrix. When I try to accomplish this ...
- 613
10
votes
0
answers
83
views
Different timing with large array assignment
Consider the following example
n = 10^8;
AbsoluteTiming[
A = ConstantArray[1., n]; // anyFunc;
A[[2 ;; ;; 2]] = -1.;
]
{0.388108, Null}
...
- 6,744
3
votes
1
answer
164
views
Possible speed improvement for numerical linear algebra?
I have a question about further optimising a numerical linear algebra calculation. I've trawled through many useful posts on this site and have ended up with something quite efficient - I was ...
- 109
2
votes
1
answer
157
views
Clarification on how Total[] can be used on multi-dimensional array
I have a rank 5 tensor that ultimately I want to modify so that for the first 3 dimensions, each element is summed together. The result will be a rank 2 tensor whose elements are the summed totals ...
- 51
12
votes
2
answers
299
views
Unexpected behavior of the procedure `Area` on the object 'Polygon'
Bug introduced in 11.3 or earlier and fixed on 12.0.
Sometimes get a results, sometimes left unevaluated.
For instance
...
- 1,760
19
votes
4
answers
638
views
Is it possible to avoid unpacking when merging Association?
For example, if we have
assoc =
AssociationThread[{1, 2, 3} -> RandomReal[1., {3, 10}]];
and
...
- 16.9k
7
votes
1
answer
368
views
Avoiding unpacking an array when altering its dimension
I am trying to flatten a matrix from 3-dimensional to 2-dimensional one.
The original one has dimension for example {10,120,120}:
...
- 683
12
votes
0
answers
126
views
What changed in String handling between 11.0 and 11.3?
I was trying to optimize some String-handling code here using my standard trick of converting it to a list of bytes first and using basic list operations instead of ...
- 46.6k
10
votes
1
answer
135
views
Why can't (partially) packed arrays be used in this example?
Bug introduced in 11.3 or earlier and persisting through 12.1 or later. Fixed in 13.0.0 or earlier
I didn't expect any difference between these:
...
- 1,116
8
votes
1
answer
229
views
How to send packed array from math kernel to 3rd party app via WSTP
Background
I'm developing a small python wrapper PyWSTP. The wrapper is still in very early stage and lacking features. One important feature I'm considering is transferring dense array between math ...
- 684
7
votes
1
answer
359
views
Packing and unpacking of arrays with Map/Table
How can I create function, that will not unpack packed arrays with Map/Table. For example I want read bytes from opened stream (this is my original goal):
...
- 886
3
votes
0
answers
70
views
PackedArray version of Chop
I'm a big fan of Chop. It's fast and useful in pre-rounding transforms and things
Unfortunately it also necessarily unpacks a real ...
- 46.6k
3
votes
1
answer
106
views
Strange unpacking of a packed array with Insert
In Mathematica 11.1.1, when a packed array is stored within another list, it gets unexpectedly unpacked when Inserting something into the outer list.
Create a ...
- 1,253
16
votes
1
answer
171
views
RandomChoice output isn't packed
Why isn't the output of RandomChoice a packed array? For instance:
RandomChoice[{.5, .2, .3} -> {1, 2, 3}, 10]
Developer`PackedArrayQ @ %
{1, 2, 3, 1, 3, 1, ...
- 129k
8
votes
2
answers
158
views
Fast function to do multiple rectangle region checks
Suppose I have a set of "rectangles" and a set of "points":
SeedRandom[5]
rects = RandomReal[10, {5, 2, 2}]
pts = RandomReal[10, {5, 2}]
{{{0.00790584, 0....
- 129k
3
votes
1
answer
134
views
revisit Table unpacking issue
This post is related to my previous post, since that post is ended. I start a new here. Because there is still something I don't understand.
define
...
- 16.9k
1
vote
0
answers
167
views
Is there a way to reduce size of complex number?
I would like to create huge matrices with hundreds of thousands of elements per side and I would like to use complex numbers in it for further processing by Mathematica functions. When I investigate ...
- 33
13
votes
3
answers
253
views
Convert Real packed array of pairs to Complex packed array
I have a Real packed array arr. It may have arbitrary depth but Last@Dimensions[arr] == 2. ...
- 232k
20
votes
2
answers
864
views
How can I determine the type of a packed array?
Packed arrays can be of type Integer, Real or Complex. Knowing that an array ...
- 232k
2
votes
0
answers
298
views
Efficiently create an array of values of a function
I have a function of four arguments, and I would like to have its values on the four-dimensional grid in an array. What is the most efficient way to produce this array, and how do I make it packed?
...
- 450
10
votes
1
answer
124
views
How to efficiently write into PackedArrays that are stored in Associations?
Using Association to generate complicated data types is very comfortable, in particular if one uses those tricks from How to make use of Associations?. However, I ...
- 103k
6
votes
1
answer
93
views
Unexpected result of Clip
A simple question. Here Clip works as documented:
Clip[0.5, {0, 0}, {0,1}]
(* 1 *)
Values larger than 0 are replaced with ...
- 10.1k
5
votes
3
answers
341
views
Efficient way to replace a value in packed array of integers
When working with integer label matrices returned by such functions as MorphologicalComponents, ImageForestingComponents etc. it ...
- 61.3k
2
votes
0
answers
84
views
Memory optimization for exporting "VideoFrames" with many large Array plots
Suppose you have 5 arrays (normalized by the number of arrays - in this case 5):
arrayList = Table[RandomChoice[Developer`ToPackedArray@{-1, 1}, {100, 100}]/5,{5}]
...
- 567
1
vote
1
answer
119
views
Reap unpacks packed arrays
I noticed that Reap unpacks packed arrays. I've looked at previous answers but am still an unsure whether this a serious issue.
E.g. consider Ex 47.3 from EIWL:
...
- 2,762
8
votes
1
answer
167
views
RegionMeasure on packed array crashes Kernel in version 11.1
Bug introduced in 11.1.0 and fixed in 11.1.1
In version 11.1.0, applying RegionMeasure or Area to a region with packed ...
- 61.3k
6
votes
1
answer
166
views
PackedArray and Dot results in undesired unpacking
General problem
I need to work with two vectors (List) of Real numbers that are quite large (each vector containing about $4\...
- 842
0
votes
1
answer
58
views
Using Set without unpacking an array
I'm trying to optimise my code by making us of packed array.
However, it appears that using Set in combination with Part ...
- 31
14
votes
0
answers
128
views
Why does MapAt unpack individual elements?
(In case this is version specific I am using Mathematica 10.1 under Windows.)
While responding to Partition array without unpacking I noticed something about MapAt ...
- 269k
3
votes
2
answers
236
views
Accelerating the construction of a ParallelTable
I wish to calculate a rather dense antisymmetric matrix quite fast based on a random distribution of points (and their radii) in the three dimensional space as follows:
...
- 491
13
votes
1
answer
401
views
Why are these timings for Pick so different?
I construct two lists, to be used in Pick as the second argument. The first one is a -1, 1 list and the second one is identical, but with -1 replaced with 0.
...
- 10.1k
1
vote
0
answers
51
views
Looking for a package for data on (sparse) uniform grids
I have large amounts of sparse 2d and 3d "volumetric" data, i.e. fixed data associated with positions in a uniform (integer coordinate) grid. I think of it as partial function
$$f: \mathbb Z^n \to D.$...
- 5,679
4
votes
3
answers
247
views
Getting directly a packed array of repeated packed arrays
Consider this code:
Needs["Developer`"];
N@Range[5];
PackedArrayQ@%
Table[%%, 5];
PackedArrayQ@%
which prints True, ...
- 1,577
13
votes
3
answers
3k
views
Fast way to export large amount of data in "Table" format
I have about a million 3D points, say
data = Table[{1. x, 1. y, 0.}, {x, 1000}, {y, 10^3}]~Flatten~1;
I want to visualize them, but ...
- 5,679
3
votes
1
answer
86
views
Nested list can not be packed?
Why can't nested list be packed?
In[252]:= ftest = {1., {3.}};
ftest = Developer`ToPackedArray[ftest];
Developer`PackedArrayQ[ftest]
Out[254]= False
- 1,570
13
votes
1
answer
345
views
Why does Outer sometimes return a packed array, and sometimes not?
For example
In[342]:=
test3 = Flatten[Outer[Plus, Range[1000], Range[1000]],
1]; // AbsoluteTiming
Out[342]= {0.0198735, Null}
returns PackedArray (...
- 16.9k
10
votes
1
answer
361
views
Speed up construction of a dense matrix
I wish to find the numerical eigenvalues of a relatively small (100 dimensional) Hermitian matrix. While the eigenvalue calculation itself is fast, the construction of the matrix is taking longer than ...
- 769
6
votes
1
answer
165
views
Why are so many built-in numerical function doesn't check its argument is packed array or not? [closed]
This question is brought by this one.
Outer[Times, RandomReal[1., 1000000], {1., 2.}];
is much slower than
...
- 16.9k