Hello all,

I dont know if everyone knows this:

I have a dualcore CPU now and was wondering how to use both cores for compiling for example lazarus.

make -j2 all

uses both cpus and works great with lazarus :)

for a quad-core use option: -j4

hope someone finds this useful

regards
alex

Does it actually works with FPC ?

Ido

http://ik.homelinux.org/

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Hi Ido,

i tested it on fpc-2.2.4 src

It seem that it works partial with FPC. Maybe the problem is that the -j option means that 2 tagets will be processed in parallel, if it is possible.
I think with FPC it is not allways possible. Compiling works but not all CPUs are used all the time.

greetings
alex

On Fri, 13 Nov 2009 17:38:20 +0100, Alexander Kaupp wrote about [Lazarus] make option -j:

This is not wholly dependent on having an SMP hardware configuration.

Even on a uniprocessor system, make can be accelerated by specifying -j2 or -j3 or even higher. This is because it is not the make program exploiting multiple processes but the Linux (or other) kernel having multiple processes to despatch (or "schedule", as UNIX boffins misname this). It doesn't need multiple CPUs, just time-slicing and enough RAM.

Of course, the more processor cores you have on your system, the higher the number that can sensibly follow -j. The rule-of-thumb I use for make is:

1. Let n denote the number of CPUs installed on the system.

2. Try 3*n+2 for the number to follow -j.

3. If that number seems too high, typically by causing paging, then try 2*n+1 instead.

So, for a monadic system, I try -j5 first, then -j3 if the machine pages.

For a dyadic system, I try -j8 first, then -j5 if the machine pages.

For a tetradic system, I try -j14 first, then -j9 if the machine pages.

... And so on.

But that is not a hard and fast rule, just a rule-of-thumb.

Note:
=====
Monadic = 1 CPU
Dyadic = 2 CPUs
Tetradic = 4 CPUs

These terms came into use in the 1960s when mainframes first acquired SMP (or "polyadic") configurations.

My dream is to have a hexadekadic box under my desk!! You should now be able to work out what that means, from the above. ... ;-)

Hi,

you are right :) I am happy to see both cpu/cores doing the compiling :)

greetings
alex

It won't make a big difference. (only making components I think)

All lcl units are compiled by fpc through the allunits.pp "project" (we use this to let fpc figure out the dependencies)
The same counts for the ide.

I hope when specifying -j2 it builds the lcl first and after that the lcl/interfaces. If not, it wont work.

So, you won't gain much.

Marc

On Fri, 13 Nov 2009 23:47:10 +0100, Marc Weustink wrote about Re: [Lazarus] make option -j:

[snip]

The make utility still has to follow the dependency graph of the project. It can only parallelize specific builds within a node of that graph.

So, you won't gain much.

Indeed, this is often the case on fairly small projects.

2009/11/14 David W Noon :

I don't even gain much when compiling fpc with -j 8 on my quad core. It makes a huge difference when compiling the kernel, but I should probably try and compare gcc. Must be a dependency issue as you say, I hope fpmake can fix this somehow.

Henry