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<Chapter><Heading> Parallel Computation - Core Functions</Heading> <Section><Heading> </Heading>
<ManSection> <Func Name="ChildProcess" Arg=""/> <Func Name="ChildProcess" Arg="arg"/> <Description> <P/> This starts a GAP session as a child process and returns a stream to the child process. If no argument is given then the child process is created on the local machine; otherwise the argument should be:<Br/> 1) <M>arg</M>="computer.ac.wales" the address of a remote computer for which ssh has been configured to require no password from the user;<Br/> (2) <M>arg</M>=["-m", "100000M", "-T"] a list of GAP command line options;<Br/> (3) <M>arg</M>="computer.ac.wales", ["-m", "100000M", "-T"] the address of a computer followed by a list of command line options. <P/> (To configure ssh so that the user can login without a password prompt from "thishost" to "remotehost" either consult "man ssh" or <Br/> <Br/> - open a shell on thishost<Br/> - cd .ssh<Br/> - ls<Br/> -> if id_dsa, id_rsa etc exists, skip the next two steps!<Br/> - ssh-keygen -t rsa<Br/> - ssh-keygen -t dsa<Br/> - scp *.pub userremotehost:~/<Br/> - ssh remotehost -l user<Br/> - cat id_rsa.pub >> .ssh/authorized_keys<Br/> - cat id_dsa.pub >> .ssh/authorized_keys<Br/> - rm id_rsa.pub id_dsa.pub<Br/> - exit<Br/> <Br/> You should now be able to connect from "thishost" to "remotehost" without a password prompt.) <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ChildClose" Arg="s"/> <Description> <P/> This closes the stream s to a child GAP process. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ChildCommand" Arg="str,s"/> <Description> <P/> This runs a GAP command <M>str</M>="cmd;" on the child process accessed by the stream s. Here "cmd;" is a string representing the command. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="NextAvailableChild" Arg="L"/> <Description> <P/> Inputs a list <M>L</M> of child processes and returns a child in <M>L</M> which is ready for computation (as soon as such a child is available). <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="IsAvailableChild" Arg="s"/> <Description> <P/> Inputs a child process <M>s</M> and returns true if s is currently available for computations, and false otherwise. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ChildPut" Arg="A,str,s"/> <Description> <P/> This copies a GAP object A on the parent process to an object B=<M>str</M> on the child process s. (The copying relies on the function PrintObj(A); ) <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="ChildGet" Arg="str,s"/> <Description> <P/> This functions copies a GAP object A="str" on the child process s and returns it on the parent process. (The copying relies on the function PrintObj(A); ) <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="HAPPrintTo" Arg="str,R"/> <Description> <P/> Inputs a string <M>str</M>="file" giving the address of a new text file and a HAP object R. It writes the object R to "file". Currently this is only implemented for R equal to a resolution. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection>
<ManSection> <Func Name="HAPRead" Arg="str,R"/> <Description> <P/> Inputs an address <M>str</M>="file" of a file containing a HAP object R and returns the object. Currently this is only implemented for R equal to a resolution. <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>1</LinkText></URL>
</Description> </ManSection> </Section> </Chapter> <Chapter> <Heading> Parallel Computation - Extra Functions</Heading> <Section><Heading> </Heading>
<ManSection> <Func Name="ChildFunction" Arg="str,s"/> <Description> <P/> This runs the GAP function <M>str</M>="function(arg);" on a child process accessed by the stream s. The output from "func;" can be accessed via the stream. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="ChildRead" Arg="s"/> <Description> <P/> This returns, as a string, the output of the last application of <M>ChildFunction("function(arg);",s)</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="ChildReadEval" Arg="s"/> <Description> <P/> This returns, as an evaluated string, the output of the last application of <M>ChildFunction("function(arg);",s)</M>. <P/><B>Examples:</B>
</Description> </ManSection>
<ManSection> <Func Name="ParallelList" Arg="I,fn,L"/> <Description> <P/> Inputs a list <M>I</M>, a function <M>fn</M> such that <M>fn(x)</M> is defined for all <M>x</M> in <M>I</M>, and a list of children <M>L</M>. It uses the children in <M>L</M> to compute <M>List(I,x->fn(x))</M>. (Obviously the function <M>fn</M> must be defined on all child processes in <M>L</M>.) <P/><B>Examples:</B> <URL><Link>../www/SideLinks/About/aboutBogomolov.html</Link><LinkText>1</LinkText></URL> , <URL><Link>../www/SideLinks/About/aboutParallel.html</Link><LinkText>2</LinkText></URL>
</Description> </ManSection> </Section> </Chapter>
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