Cell software development: Difference between revisions

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'''Software development''' for the [[Cell microprocessor]] involves a mixture of conventional development practices for the [[Power ArchitecturePowerPC]]-compatible PPU core, and novel software development challenges with regardsregard to the functionally reduced SPU coprocessors.

{{Cell microprocessor segments}}

'''Software development''' for the [[Cell microprocessor]] involves a mixture of conventional development practices for the [[Power Architecture]]-compatible PPU core, and novel software development challenges with regards to the functionally reduced SPU coprocessors.

==Linux on Cell==

An open source software-based strategy was adopted to accelerate the development of a Cell BE ecosystem and to provide an environment to develop Cell applications, including a GCC-based Cell compiler, binutils and a port of the Linux operating system.<ref name="research.ibm.com">{{cite web|url=http://www.research.ibm.com/people/m/mikeg/papers/2007_ieeecomputer.pdf|format=PDF|title=An Open Source Environment for Cell Broadband Engine System Software|date=June 2007}}</ref>

==Octopiler==

'''Octopiler''' is [[IBM]]'s prototype [[compiler]] to allow [[software developer]]s to write [[software code|code]] for [[Cell processor]]s.<ref>{{citation|title=Using advanced compiler technology to exploit the performance of the Cell Broadband Engine architecture|date=2017-10-23|url=http://www.research.ibm.com/journal/sj/451/eichenberger.html|archive-url=https://web.archive.org/web/20060411094457/http://www.research.ibm.com/journal/sj/451/eichenberger.html|archive-date=2006-04-11|url-status=dead|publisher=IBM Systems Journal}}</ref><ref>{{Cite web|date=2006-01-20|title=Compiler Technology for Scalable Architectures|url=https://www.empat.tech/services|archive-url=https://web.archive.org/web/20080320071448/http://domino.research.ibm.com/comm/research_projects.nsf/pages/cellcompiler.index.html|archive-date=2008-03-20|access-date=2025-06-11|website=IBM Research|language=en-us}}</ref><ref>{{Cite web|last=Stokes|first=Jon|date=2006-02-26|title=IBM's Octopiler, or, why the PS3 is running late|url=https://arstechnica.com/uncategorized/2006/02/6265-2/|access-date=2025-06-11|website=Ars Technica}}</ref>

==Software portability==

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====Differences between VMX and SPU====

The [[Vector Multimedia ExtensionsAltiVec|VMX]] (Vector Multimedia Extensions) technology is conceptually similar to the vector model provided by the SPU processors, but there are many significant differences.

{| class="wikitable" style="margin: 1em auto 1em auto"

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| 32 bits || 32 bits

|-

! number of [[Processor register (computer science)|registers]]

| 32 <!-- p.28/333 --> || 128

<!-- p.34/333 also shows 32 GP and 32 FP regs, are these part of VMX? -->

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| big (default), little <!--p.44/333 --> || big endian

|-

! [[floating Floating-point (computer science)arithmetic|floating point]] modes

| Java, non-Java || single precision, IEEE double

|-

! [[memoryData (computerstructure science)alignment|memory]]Memory alignment]]

| quadword only || quadword only

|}

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====Porting VMX code for SPU====

ThereA issubstantial a great bodyamount of codeVMX which([[Altivec]]) has beencode developed for other [[IBM [[Power processorsmicroprocessors]], that could potentially be adapted and recompiled to run on the SPU. This code base includes VMX code that runsparticularly under the [[PowerPC]] version of [[Apple Computer|Apple'smacOS]], [[Maccan OSpotentially X]],be whereadapted itfor isuse betteron knownthe as [[Altivec]]SPU. DependingThe onfeasibility howof manyporting VMXdepends specific features are involved,on the adaptationextent involvedof canVMX-specific rangefeatures anywhereused—ranging from straightforward, to onerous, to completely impractical. TheHowever, most importantkey workloads fortypically themap SPUwell generallyto mapthe quiteSPU wellarchitecture.

In some cases it is possible to port, existing VMX code can be ported directly. If the VMX code is highly generic (makes few assumptions about the execution environment) the translation can be relatively straightforward. The two processors specify a different [[binary format|binary code format]], so recompilation is required at a minimum. Even where [[Instruction (computer science)|instructions]] exist with the same behaviors, they do not have the same instruction names, so this must be mapped as well. IBM's providesdevelopment toolkit includes compiler [[intrinsicintrinsics function|intrinsic]]sthat whichautomate take caremuch of this mapping transparently as part of the development toolkit.

In many cases, however, a directly equivalent instruction does not exist. The workaround might be obvious or it might not. For example, if saturation behavior is required on the SPU, it can be coded by adding additional SPU instructions to accomplish this (with some loss of efficiency). At the other extreme, if Java floating-point semantics are required, this is almost impossible to achieve on the SPU processor. To achieve the same computation on the SPU might require that an entirely different [[algorithm]] be written from scratch.

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Transferring data between the local stores of different SPUs can have a large performance cost. The local stores of individual SPUs can be exploited using a variety of strategies.

Applications with high locality, such as dense matrix computations, represent an ideal workload class for the local stores in Cell BE.<ref>{{cite web|url=http://www.research.ibm.com/people/m/mikeg/papers/2006_ieeemicro.pdf|format=PDF|title=Synergistic Processing in Cell's Multicore Architecture|date=March 2006}}</ref>

Streaming computations can be efficiently accommodated using [[software pipelining]] of memory block transfers using a multi-buffering strategy.<ref name="research.ibm.com"/>

The software cache offers a solution for random accesses.<ref>{{cite web|url=http://www.research.ibm.com/journal/sj/451/eichenberger.pdf|format=PDF|title=Using advanced compiler technology to exploit the performance of the Cell Broadband Engine architecture|date=January 2006}}</ref>

More sophisticated applications can use multiple strategies for different data types.<ref>{{cite web|url=http://www.research.ibm.com/cell/papers/2008_vee_cellgc.pdf|format=PDF|title=Cell GC: Using the Cell Synergistic Processor as a Garbage Collection Coprocessor |date=March 2008}}</ref>

==Compiler-mediated parallelism==

==References==

* [http://www.research.ibm.com/cell/ The Cell Project at IBM Research]

* [http://cag.csail.mit.edu/crg/papers/eichenberger05cell.pdf Optimizing Compiler for a CELL Processor]

* [httphttps://dx.doi.org/10.1147/sj.451.0059 Using advanced compiler technology to exploit the performance of the Cell Broadband Engine architecture] <!-- repackaging of Eichberger ''et al.'' above -->

* [http://domino.research.ibm.com/comm/research_projects.nsf/pages/cellcompiler.index.html Compiler Technology for Scalable Architectures]

{{reflist}}

{{Cell microprocessor segments}}

;Notes

<references/>

{{DEFAULTSORT:Cell Software Development}}

[[Category:Cell BE architecture]]

[[Category:Compilers]]

[[Category:Vaporware]]