Currently for a task, I am working with input files which give Matrix related test cases (Matrix Multiplication) i.e., example of an input file ->
N M
1 3 5 ... 6 (M columns)
....
5 4 2 ... 1 (N rows)
I was using simple read() to access them till now, but this is not efficient for large files of size > 10^2.
So I wanted to know is there some way to use processes to do this in parallel.
Also I was thinking of using multiple IO readers based on line, so then each process could read different segments of the file but couldn't find any helpful resources.
Thank you.
PS: Current code is using this:
io:fread(IoDev, "", "~d")
Did you consider to use re module? I did not make a performance test, but it may be efficient. In the following example I do not use the first "M N" line. So I did not put it in the matrix.txt file.
matrix file:
1 2 3 4 5 6 7 8 9
11 12 13 14 15 16 17 18 19
21 22 23 24 25 26 27 28 29
31 32 33 34 35 36 37 38 39
I made the conversion in the shell
1> {ok,B} = file:read_file("matrix.txt"). % read the complete file and store it in a binary
{ok,<<"1 2 3 4 5 6 7 8 9\r\n11 12 13 14 15 16 17 18 19\r\n21 22 23 24 25 26 27 28 29\r\n31 32 33 34 35 36 37 38 39">>}
2> {ok,ML} = re:compile("[\r\n]+"). % to split the complete binary in a list a binary, one for each line
{ok,{re_pattern,0,0,0,
<<69,82,67,80,105,0,0,0,0,0,0,0,1,8,0,0,255,255,255,255,
255,255,...>>}}
3> {ok,MN} = re:compile("[ ]+"). % to split the line into binaries one for each integer
{ok,{re_pattern,0,0,0,
<<69,82,67,80,73,0,0,0,0,0,0,0,17,0,0,0,255,255,255,255,
255,255,...>>}}
4> % a function to split a line and convert each chunk into integer
4> F = fun(Line) -> Nums = re:split(Line,MN), [binary_to_integer(N) || N <- Nums] end.
#Fun<erl_eval.7.126501267>
5> Lines = re:split(B,ML). % split the file into lines
[<<"1 2 3 4 5 6 7 8 9">>,<<"11 12 13 14 15 16 17 18 19">>,
<<"21 22 23 24 25 26 27 28 29">>,
<<"31 32 33 34 35 36 37 38 39">>]
6> lists:map(F,Lines). % map the function to each lines
[[1,2,3,4,5,6,7,8,9],
[11,12,13,14,15,16,17,18,19],
[21,22,23,24,25,26,27,28,29],
[31,32,33,34,35,36,37,38,39]]
7>
if you want to check the matrix size, you can replace the last line with:
[[NbRows,NbCols]|Matrix] = lists:map(F,Lines),
case (length(Matrix) == NbRows) andalso
lists:foldl(fun(X,Acc) -> Acc andalso (length(X) == NbCols) end,true,Matrix) of
true -> {ok,Matrix};
_ -> {error_size,Matrix}
end.
is there some way to use processes to do this in parallel.
Of course.
Also I was thinking of using multiple IO readers based on line, so
then each process could read different segments of the file but
couldn't find any helpful resources.
You don't seek to positions in a file by line, rather you seek to byte positions. While a file may look like a bunch of lines, a file is actually just one long sequence of characters. Therefore, you will need to figure out what byte positions you want to seek to in the file.
Check out file:position, file:pread.
I am trying to write awk script that generate 3 natural numbers that sum to 60. I am trying with rand function but I`ve got problem with sum to 60
Here is one way:
awk -v n=60 'BEGIN{srand();a=int(rand()*n);b=int(rand()*(n-a));c=n-a-b;
print a,b,c}'
Idea is:
generate random number a :0=<a<60
generate random number b :0=<b<60-a
c=60-a-b
here, I set a variable n=60, to make it easy if you have other sum.
If we run this one-liner 10 times, we get output:
kent$ awk 'BEGIN{srand();for(i=1;i<=10;i++){a=int(rand()*60);b=int(rand()*(60-a));c=60-a-b;print a,b,c}}'
46 7 7
56 1 3
26 15 19
14 12 34
44 6 10
1 36 23
32 1 27
41 0 19
55 1 4
54 1 5
I've already checked a similarly existing topic (How to read numeric data from a string in FORTRAN), but I'm not being able to do what I want.
I need to open a file and read a numeric value from a string. Bellow there's a section of the file in question. I want to read the integer next to 'ELEMENTS:', but so far I'm not being able to do so.
ELEMENT GROUP 2.4.6
GROUP: 1 ELEMENTS: 187169 MATERIAL: 2 NFLAGS: 1
fluid
0
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
Can someone please help me here?
Ok guys, thanks to your answers the program is working!
For further reference, here's the reading part of the code:
READ(77,'(A)') str
ipos = INDEX(str,"ELEMENTS:",back=.true.) + 9
READ (str(1+ipos:),*) k
PRINT*, k
Thank for the answers.
In man page of SORT, it says you can set a random source like:
$ sort some.txt --random-sort --random-source=/dev/urandom
I want to an standard output text to the source like:
$ sort some.txt --random-sort --random-source=`date +"%m%d%H%M"`
But this only says:
open failed: 11021103: No such file or directory
How can I do this?
Here's a simple python script that takes a seed and outputs random bytes:
> cat rand_bits.py
import random
import sys
if len(sys.argv) > 1:
rng = random.Random(int(sys.argv[-1]))
else:
rng = random.Random(0xBA5EBA11)
try:
while True:
sys.stdout.write(chr(rng.getrandbits(8)))
except (IOError, KeyboardInterrupt):
pass
sys.stdout.close()
You can just feed those bytes straight into sort:
> sort <(seq 25) -R --random-source=<(python rand_bits.py 5)
8
2
4
7
10
19
17
11
3
20
14
18
1
16
25
12
5
21
24
23
22
9
15
13
6
By the way, the input can be any file, but the file better be long enough!
> sort <(seq 25) -R --random-source=<(date +"%m%d%H%M")
sort: /dev/fd/12: end of file
> sort <(seq 25) -R --random-source=/dev/sda1
3
13
24
5
10
16
4
17
12
18
14
2
6
15
23
21
19
11
9
1
20
25
22
8
7
Are there an efficient algorithm to search and dump all common substrings (which length is 3 or longer) between 2 strings?
Example input:
Length : 0 5 10 15 20 25 30
String 1 : ABC-DEF-GHI-JKL-ABC-ABC-STU-MWX-Y
String 2 : ABC-JKL-MNO-ABC-DEF-PQR-DEF-ZWX-Y
Example output:
In string 1 2
---------------------------
ABC-DEF 0 12
ABC-DE 0 12
BC-DEF 1 13
:
-ABC- 15,19 11
-JKL- 11 3
-DEF- 3 15
-JKL 11 3
JKL- 12 4
-DEF 3 15,23
DEF- 4 16
WX-Y 29 29
ABC- 0,16,20 0,12
-ABC 15,19 11
DEF- 4 16,24
DEF 4 16,24
ABC 0,16,20 0,12
JKL 12 4
WX- 29 29
X-Y 30 30
-AB 15,19 11
BC- 1,17,21 1,13
-DE 3 15,23
EF- 5 17,25
-JK 11 3
KL- 13 5
:
In the example, "-D", "-M" is also a common substring but is not required, because it's length is only 2. (There might be some missing outputs in example because there are so many of them...)
You can find all common substrings using a data structure called a Generalized suffix tree
Libstree contains some example code for finding the longest common substring. That example code can be modified to obtain all common substrings.