[MacPorts] #28512: atlas wont compile

[MacPorts]

#28512: atlas wont compile
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 Reporter:  macports@…              |       Owner:  jameskyle@…           
     Type:  defect                  |      Status:  new                   
 Priority:  Normal                  |   Milestone:                        
Component:  ports                   |     Version:  1.9.99                
 Keywords:                          |        Port:  atlas                 
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Comment(by ryandesign@…):

 Individual ports can't just decide to build for some other architecture.
 There are consequences. MacPorts ''will'' record in the registry that it
 ''has'' built the port for ${build_arch}; if that's not true and the port
 has actually built for some other architecture without telling MacPorts,
 then the registry would contain inaccurate information.

 The registry is used when dealing with dependencies and dependents. If
 atlas is going to build for ppc64, then all of its dependencies -- gcc44,
 bzip2, gzip -- need to be built for ppc64 as well. Furthermore, any port
 that depends on atlas will also need to build ppc64. Basically you'd be
 forcing all G5 users who have atlas installed to set build_arch to ppc64
 and rebuild all ports, which I consider a very drastic thing to make them
 do, especially considering, as I mentioned above, that ppc64 is not the
 default build_arch on any Mac, meaning it has not received much testing
 and there are probably many ports broken under that arch.

 I don't know what the advantages for atlas are for building ppc64. I
 understand that in general ppc64 has few benefits over ppc. Obviously
 there's the ability to deal with more than 4GB of data in a single
 process; the only other noticeable difference I'm aware of is that memory
 addresses take twice as much space to store, so you can fit fewer of them
 in cache, which could actually hurt performance. This is in stark contrast
 to the difference between i386 and x86_64; x86_64 adds additional
 registers and fixes several problems with the legacy i386 architecture,
 thus offering several speed and efficiency benefits over i386 beyond the
 ability to address more memory.

 Feel free to add a ui_msg to atlas that alerts G5 owners who have
 build_arch set to ppc that they might have better performance by switching
 to ppc64. If you insist atlas must build 64-bit on G5s, then you must set
 configure.build_arch to ppc64 on G5s. However, I don't think it's nice to
 impose a manual all-port rebuild of an untested build_arch on G5 owners.

-- 
Ticket URL: <https://trac.macports.org/ticket/28512#comment:65>
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