Re^2: Getting/handling big files w/ perl

From your description, I doubt that the process could be tremendously improved as it stands: the process is I/O-bound and the I/O capabilities of the machine are lackluster. The process could be realistically (but, perhaps significantly) improved by re-defining it and then, as others suggested, “throwing silicon at” (the re-defined process).

Now to debunk Yet Another of your Inglorious Theories.

This shows a perl program downloading an 11MB file using 1,2,4,8,16 & 32 concurrent streams, on my 4 core CPU, across my relatively tardy 20Mb/s connection:

C:\test>1107326 -T=1 http://************/goldenPath/hg19/chromosomes/c
+hr21.fa.gz
Fetching 11549785 bytes in 1 x 11549786 streams
Received 11549785 bytes
Took 55.765514851 secs

C:\test>1107326 -T=2 http://************/goldenPath/hg19/chromosomes/c
+hr21.fa.gz
Fetching 11549785 bytes in 2 x 5774893 streams
Received 11549785 bytes
Took 27.654243946 secs

C:\test>1107326 -T=4 http://************/goldenPath/hg19/chromosomes/c
+hr21.fa.gz
Fetching 11549785 bytes in 4 x 2887447 streams
Received 11549785 bytes
Took 15.210910082 secs

C:\test>1107326 -T=8 http://************/goldenPath/hg19/chromosomes/c
+hr21.fa.gz
Fetching 11549785 bytes in 8 x 1443724 streams
Received 11549785 bytes
Took 9.515606880 secs

C:\test>1107326 -T=16 http://************/goldenPath/hg19/chromosomes/
+chr21.fa.gz
Fetching 11549785 bytes in 16 x 721862 streams
Received 11549785 bytes
Took 8.902327061 secs

C:\test>1107326 -T=32 http://************/goldenPath/hg19/chromosomes/
+chr21.fa.gz
Fetching 11549785 bytes in 32 x 360931 streams
Received 11549785 bytes
Took 16.386690140 secs
[download]

As you can see, you get diminishing returns from the concurrency, but over provisioning the 4 core CPU to manage 16 concurrent IO-bounds threads results in the best throughput.

And how does that compare to using WGET and a single thread on the same connection and processor:

C:\test>wget  http://************/goldenPath/hg19/chromosomes/chr21.fa
+.gz
--2014-11-17 11:38:37--  http://************/goldenPath/hg19/chromosom
+es/chr21.fa.gz
Resolving ************... 128.114.119.***
Connecting to ************|128.114.119.***|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 11549785 (11M) [application/x-gzip]
Saving to: `chr21.fa.gz'

100%[=================================================================
+===================>] 11,549,785   379K/s   in 32s

2014-11-17 11:39:30 (352 KB/s) - `chr21.fa.gz' saved [11549785/1154978
+5]
[download]

It beats it hands down!

************ server name redacted to discourage the world+dog from hitting them by way of comparison.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

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