I meet the following statement in a code. Can somebody explain it to me, please?
My problem is mostly with the number 0.80. Where do we get it? I know that Math.random generates numbers between 0-0.99.
if (Math.random() > 0.80) { ... }
They are trying to create a if statement that gets executed randomly about 20% of the time.
the 0.80 is just a 'magic number' for their particular application. For example changing it from 0.80 to 0.50 would result in the if statement getting executed about 50% of the time.
Related
I'm trying to find a more efficient and speedier way (if possible) to pull subsets of observations that meet certain criteria from multiple hospital claims datasets in SAS. A simplified but common type of data pull would look like this:
data out.qualifying_patients;
set in.state1_2017
in.state1_2018
in.state1_2019
in.state1_2020
in.state2_2017
in.state2_2018
in.state2_2019
in.state2_2020;
array prcode{*} I10_PR1-I10_PR25;
do i=1 to 25;
if prcode{i} in ("0DTJ0ZZ","0DTJ4ZZ") then cohort=1;
end;
if cohort=1 then output;
run;
Now imagine that instead of 2 states and 4 years we have 18 states and 9 years -- each about 1GB in size. The code above works fine but it takes FOREVER to run on our non-optimized server setup. So I'm looking for alternate methods to perform the same task but hopefully at a faster clip.
I've tried including (KEEP=) or (DROP=) statements for each dataset included the SET statement to limit the variables being scanned, but this really didn't have much of an impact on speed -- and, for non-coding-related reasons, we pretty much need to pull all the variables.
I've also experimented a bit with hash tables but it's too much to store in memory so that didn't seem to solve the issue. This also isn't a MERGE issue which seems to be what hash tables excel at.
Any thoughts on other approaches that might help? Every data pull we do contains customized criteria for a given project, but we do these pulls a lot and it seems really inefficient to constantly be processing thru the same datasets over and over but not benefitting from that. Thanks for any help!
I happend to have a 1GB dataset on my compute, I tried several times, it takes SAS no more than 25 seconds to set the dataset 8 times. I think the set statement is too simple and basic to improve its efficient.
I think the issue may located at the do loop. Your program runs do loop 25 times for each record, may assigns to cohort more than once, which is not necessary. You can change it like:
do i=1 to 25 until(cohort=1);
if prcode{i} in ("0DTJ0ZZ","0DTJ4ZZ") then cohort=1;
end;
This can save a lot of do loops.
First, parallelization will help immensely here. Instead of running 1 job, 1 dataset after the next; run one job per state, or one job per year, or whatever makes sense for your dataset size and CPU count. (You don't want more than 1 job per CPU.). If your server has 32 cores, then you can easily run all the jobs you need here - 1 per state, say - and then after that's done, combine the results together.
Look up SAS MP Connect for one way to do multiprocessing, which basically uses rsubmits to submit code to your own machine. You can also do this by using xcmd to literally launch SAS sessions - add a parameter to the SAS program of state, then run 18 of them, have them output their results to a known location with state name or number, and then have your program collect them.
Second, you can optimize the DO loop more - in addition to the suggestions above, you may be able to optimize using pointers. SAS stores character array variables in memory in adjacent spots (assuming they all come from the same place) - see From Obscurity to Utility:
ADDR, PEEK, POKE as DATA Step Programming Tools from Paul Dorfman for more details here. On page 10, he shows the method I describe here; you PEEKC to get the concatenated values and then use INDEXW to find the thing you want.
data want;
set have;
array prcode{*} $8 I10_PR1-I10_PR25;
found = (^^ indexw (peekc (addr(prcode[1]), 200 ), '0DTJ0ZZ')) or
(^^ indexw (peekc (addr(prcode[1]), 200 ), '0DTJ4ZZ'))
;
run;
Something like that should work. It avoids the loop.
You also could, if you want to keep the loop, exit the loop once you run into an empty procedure code. Usually these things don't go all 25, at least in my experience - they're left-filled, so I10_PR1 is always filled, and then some of them - say, 5 or 10 of them - are filled, then I10_PR11 and on are empty; and if you hit an empty one, you're all done for that round. So not just leaving when you hit what you are looking for, but also leaving when you hit an empty, saves you a lot of processing time.
You probably should consider a hardware upgrade or find someone who can tune your server. This paper suggests tips to improve the processing of large datasets.
Your code is pretty straightforward. The only suggestion is to kill the loop as soon as the criteria is met to avoid wasting unnecessary resources.
do i=1 to 25;
if prcode{i} in ("0DTJ0ZZ","0DTJ4ZZ") then do;
output; * cohort criteria met so output the row;
leave; * exit the loop immediately;
end;
end;
Problem
Howdy guys, so I want to find the run time of a block of code in Ruby, but I am not entirely sure as to how I could do it. I want to run some code, and then output how long it took to run that code because I have a super huge program and the run time changes a lot. I want to make sure it always has a consistent run time (I could do it by sleeping it for a fraction of a second) but that isn't my problem. I want to find out how long the run time actually is so the program can know if it needs to slow things down or speed things up.
My Thoughts
So, I have an idea as to how it could work. I have never used Time in ruby but I have an idea as to how I could use that. I could have a variable equal to the time (in milliseconds) and then another variable that I make at the end of the code block that does it again, and then I just subtract them, but I have (1) never used Time and (2) I don't actually know if that is the best way.
Thanks in advance!
Ruby has the Benchmark module for timing how long things take. I've never used this outside of seeing if a method is taking too long to run, etc. in development, not sure if this is 'recommended' for production code or for keeping things above a minimum runtime (as it sounds like you might be doing), but take a look and see how it feels for your use case.
It also sounds like you might be interested in the Timeout module as well (for making sure things don't take longer than a set amount of time).
If you really have a use case for making sure something takes a minimum amount of time, timing the code (either using a Benchmark method or just Time or another solution) and then sleep the difference is the only thing that comes to mind.
It is simple. Look at your watch (Time.now) and remember the time, run the code, look at your watch again, subtract.
t0 = Time.now
# your block of code
puts Time.now - t0
[http://ruby-doc.org/core-1.9.3/Time.html
You want to to use the Time object. (Time Docs)
For example,
start = Time.now
# code to time
finish = Time.now
diff = finish - start
diff would be in seconds, as a floating point number.
EDIT: end is reserved.
or you can use
require 'benchmark'
def foo
time = Benchmark.measure {
code to test
}
puts time.real #or save it to logs
end
Sample output:
2.2.3 :001 > foo
5.230000 0.020000 5.250000 ( 5.274806)
Values are CPU time, system time, total and real elapsed time.
[http://ruby-doc.org/stdlib-2.0.0/libdoc/benchmark/rdoc/Benchmark.html#method-c-bm
Source: Ruby docs.
Solved:
It turns out to be a mistake in my UDTF. I find out a fix but I don't quite understand why it worked. At the beginning when I was implementing the UDTF, Eclipse suggested that initialize is deprecated. But I got error if I skip it, so I implemented it anyway. I put a variable initialization in that method, guessing init is only to be done once. The jar worked for some simpler scenarios, but if I were to use the UDTF output with a UDF, then use the UDF output to do something, like the cheating cluster by or insert, I got the previously mentioned error. The engineer friend of mine found out that the initialize actually got executed more than once. So I just put the initialization in process, with a if checking if the variable is null, and init it if is. Then everything works fine, my cheat also worked. Still, if someone can give me an explanation, I would be most grateful.
Following is my original question:
I know I'm not supposed to use cluster by after UDTF, so select myudtf("stringValue") cluster by rand() wouldn't work.
But since my udtf outputs 7000+ and growing rows every hour, so I really need to distribute the subsequent processing to all my hadoop cluster slave units.
And I imagine I don't get that without using cluster by rand(), so I tried the following cheat:
First I wrap the result up with an other table, select key from (select myudtf("stringValue") as key) t limit 1; and it gives correct result,
OK
some/key/value/string
Time taken: 0.035 seconds, Fetched: 1 row(s)
Then I add the cluster by part, select key from (select myudtf("stringValue") as key) t cluster by rand() limit 1, then I get error:
WARNING: Hive-on-MR is deprecated in Hive ...
....
Task with the most failures(4):
-----
Task ID:
task_....
URL:
http:....
....
-----
Diagnostic Messages for this Task:
Error: tried to access class sun.security.ssl.SSLSessionContextImpl from class sun.security.ssl.SSLSessionContextImplConstructorAccess
FAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask
MapReduce Jobs Launched:
Stage-Stage-1: Map: 1 Reduce: 1 HDFS Read: 0 HDFS Write: 0 FAIL
Total MapReduce CPU Time Spent: 0 msec
I did this trying to cheat hive to treat the temporary table t as a "normal" table which I can apply cluster by to, hoping that it will distribute the work load to all the hadoop slaves, but unfortunately hive is clever enough to see through my poorly attempted trick.
So, could some one please help me to clarify my mis-conceptions, or give me some hint of the correct way to do this?
FYI I asked help from a highly experienced engineering guy in my company, and he thinks it maybe a deeper system level bug, he tried to trace the problem for 20 something minutes before he left work, he did find some lib version issues but couldn't fix the problem after all. ...And I just guess it must be something I did wrongly.
It turns out to be a mistake in my UDTF. I find out a fix but I don't quite understand why it worked. At the beginning when I was implementing the UDTF, Eclipse suggested that initialize is deprecated. But I got error if I skip it, so I implemented it anyway. I put a variable initialization in that method, guessing init is only to be done once. The jar worked for some simpler scenarios, but if I were to use the UDTF output with a UDF, then use the UDF output to do something, like the cheating cluster by or insert, I got the previously mentioned error. The engineer friend of mine found out that the initialize actually got executed more than once. So I just put the initialization in process, with a if checking if the variable is null, and init it if is. Then everything works fine, my cheat also worked. Still, if someone can give me a more specific explanation, I would be most grateful.
I am about to write a text based adventure game in Prolog, therefore i have tons of writeline statements. I was wondering if i could slow down the output processing of my text. So imagine the following scenario:
I have a Textblock A that gets printed and i want a 2 sec delay afterwards.
So Textblock B gets printed 2 sec later, without the :- sign in Prolog.
My first idea was to write a loop that compares the current time with currenttime + 2 s but i cant get rid of the :- sign.
Unfortunately; I am a newbie in Prolog and Ii don't have any clue about the thread handling.
That statement might be useful but it doesn't work at all:
delayText([H|T]) :-
put_char(H),
flush_output,
sleep(0.1),
delayText(T).
delayText([]).
Neither flush output nor sleep seem to work.
I'm using ProDT in Eclipse.
Thanks in advance,
Chris.
I'm not sure as to how you want to realise the writing for your game, but sleep/1 as used in the example code in your question can be used together with a simple write like so:
delayText([]).
delayText([H|T]) :-
write(H),
sleep(1), % Time in seconds
delayText(T).
While using ruby-prof, printed out in graph-html mode, the report for one method says (with some snipping)
%Total %Self Total Self Wait Child Calls Name Line
52.85% 0.00% 51.22 0.00 0.00 51.22 1 ClassName#method_name 42
51.22 0.00 0.00 51.22 1/3 Hash#each 4200
Obviously, it's not Hash#each that's taking a long time, but the yield block within Hash#each.
Looking at the report for Hash#each is confusing because it reports on all of the code called by anything that uses Hash#each.
Is it possible to ask ruby-prof to put the information on yielded code in ClassName#method_name's report?
Using min_percent or switching to a flat profile doesn't seem to help.
Version 0.9.0 of ruby-prof allows method elimination. For example, to eliminate Integer#times, use
result = RubyProf.stop
result.eliminate_methods!([/Integer#times/])
so that
def method_a
5.times {method_b}
end
will indicate the relationship between method_a and method_b directly.
If you don't mind low-tech, maybe you want to consider this. All you need is to be able to pause the debugger. Guaranteed, it will quickly find anything you can find any other way, and not show you any irrelevant code.