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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@6538 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2011-07-18 15:22:14 +00:00
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78
doc/Section_start.html
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@ -341,6 +341,45 @@ Obj_name where it stores the system-specific *.o files.
files created when LAMMPS is built, for either all builds or for a
particular machine.
</P>
<P>(3) Changing the size limits in src/lmptype.h
</P>
<P>If you are running a very large problem (billions of atoms or more)
and get a run-time error about the system being too big, either on a
per-processor basis or in total size, then you may need to change one
or more settings in src/lmptype.h and re-compile LAMMPS.
</P>
<P>As the documentation in that file explains, you have basically
two choices to make:
</P>
<UL><LI>set the data type size of integer atom IDs to 4 or 8 bytes
<LI>set the data type size of integers that store the total system size to 4 or 8 bytes
</UL>
<P>The default for atom IDs is 4-byte integers since there is a memory
and communication cost for 8-byte integers. Non-molecular problems do
not need atom IDs so this does not restrict their size. Molecular
problems (which use IDs to define molecular topology), are limited to
about 2 billion atoms (2^31) with 4-byte IDs. With 8-byte IDs they
are effectively unlimited in size (2^63).
</P>
<P>The default for total system size quantities (like the number of atoms
or timesteps) is 8-byte integers by default which is effectively
unlimited in size (2^63). If your system or MPI implementation does
not support 8-byte integers, an error will be generated, and you will
need to set "bigint" to 4-byte integers. This restricts your total
system size to about 2 billion atoms or timesteps (2^31).
</P>
<P>Note that in src/lmptype.h there are also settings for the MPI data
types associated with the integers that store atom IDs and total
system sizes, which need to be set consistent with the associated C
data types.
</P>
<P>In all cases, the size of problem that can be run on a per-processor
basis is limited by 4-byte integer storage to about 2 billion atoms
per processor (2^31), which should not normally be a restriction since
such a problem would have a huge per-processor memory footprint due to
neighbor lists and would run very slowly in terms of CPU
secs/timestep.
</P>
<HR>
<A NAME = "2_2_6"></A><B><I>Building for a Mac:</I></B>
@ -377,45 +416,6 @@ third includes all standard packages (with the exceptions) and some
user packages. The included user packages are USER-EFF, USER-CG-CMM,
and USER-REAXC. The fourth project includes the USER-AWPMD package.
</P>
<P>(5) Changing the size limits in src/lmptype.h
</P>
<P>If you are running a very large problem (billions of atoms or more)
and get a run-time error about the system being too big, either on a
per-processor basis or in total size, then you may need to change one
or more settings in src/lmptype.h and re-compile LAMMPS.
</P>
<P>As the documentation in that file explains, you have basically
two choices to make:
</P>
<UL><LI>set the data type size of integer atom IDs to 4 or 8 bytes
<LI>set the data type size of integers that store the total system size to 4 or 8 bytes
</UL>
<P>The default for atom IDs is 4-byte integers since there is a memory
and communication cost for 8-byte integers. Non-molecular problems do
not need atom IDs so this does not restrict their size. Molecular
problems (which use IDs to define molecular topology), are limited to
about 2 billion atoms (2^31) with 4-byte IDs. With 8-byte IDs they
are effectively unlimited in size (2^63).
</P>
<P>The default for total system size quantities (like the number of atoms
or timesteps) is 8-byte integers by default which is effectively
unlimited in size (2^63). If your system does not support 8-byte
integers, an error will be generated, and you will need to set
"bigint" to 4-byte integers. This restricts your total system size to
about 2 billion atoms or timesteps (2^31).
</P>
<P>Note that in src/lmptype.h there are also settings for the MPI data
types associated with the integers that store atom IDs and total
system sizes, which need to be set consistent with the associated C
data types.
</P>
<P>In all cases, the size of problem that can be run on a per-processor
basis is limited by 4-byte integer storage to about 2 billion atoms
per processor (2^31), which should not normally be a restriction since
such a problem would have a huge per-processor memory footprint due to
neighbor lists and would run very slowly in terms of CPU
secs/timestep.
</P>
<HR>
<H4><A NAME = "2_3"></A>2.3 Making LAMMPS with optional packages

78
doc/Section_start.txt
View File

@ -336,6 +336,45 @@ Typing "make clean-all" or "make clean-foo" will delete *.o object
files created when LAMMPS is built, for either all builds or for a
particular machine.
(3) Changing the size limits in src/lmptype.h
If you are running a very large problem (billions of atoms or more)
and get a run-time error about the system being too big, either on a
per-processor basis or in total size, then you may need to change one
or more settings in src/lmptype.h and re-compile LAMMPS.
As the documentation in that file explains, you have basically
two choices to make:
set the data type size of integer atom IDs to 4 or 8 bytes
set the data type size of integers that store the total system size to 4 or 8 bytes :ul
The default for atom IDs is 4-byte integers since there is a memory
and communication cost for 8-byte integers. Non-molecular problems do
not need atom IDs so this does not restrict their size. Molecular
problems (which use IDs to define molecular topology), are limited to
about 2 billion atoms (2^31) with 4-byte IDs. With 8-byte IDs they
are effectively unlimited in size (2^63).
The default for total system size quantities (like the number of atoms
or timesteps) is 8-byte integers by default which is effectively
unlimited in size (2^63). If your system or MPI implementation does
not support 8-byte integers, an error will be generated, and you will
need to set "bigint" to 4-byte integers. This restricts your total
system size to about 2 billion atoms or timesteps (2^31).
Note that in src/lmptype.h there are also settings for the MPI data
types associated with the integers that store atom IDs and total
system sizes, which need to be set consistent with the associated C
data types.
In all cases, the size of problem that can be run on a per-processor
basis is limited by 4-byte integer storage to about 2 billion atoms
per processor (2^31), which should not normally be a restriction since
such a problem would have a huge per-processor memory footprint due to
neighbor lists and would run very slowly in terms of CPU
secs/timestep.
:line
[{Building for a Mac:}] :link(2_2_6)
@ -372,45 +411,6 @@ third includes all standard packages (with the exceptions) and some
user packages. The included user packages are USER-EFF, USER-CG-CMM,
and USER-REAXC. The fourth project includes the USER-AWPMD package.
(5) Changing the size limits in src/lmptype.h
If you are running a very large problem (billions of atoms or more)
and get a run-time error about the system being too big, either on a
per-processor basis or in total size, then you may need to change one
or more settings in src/lmptype.h and re-compile LAMMPS.
As the documentation in that file explains, you have basically
two choices to make:
set the data type size of integer atom IDs to 4 or 8 bytes
set the data type size of integers that store the total system size to 4 or 8 bytes :ul
The default for atom IDs is 4-byte integers since there is a memory
and communication cost for 8-byte integers. Non-molecular problems do
not need atom IDs so this does not restrict their size. Molecular
problems (which use IDs to define molecular topology), are limited to
about 2 billion atoms (2^31) with 4-byte IDs. With 8-byte IDs they
are effectively unlimited in size (2^63).
The default for total system size quantities (like the number of atoms
or timesteps) is 8-byte integers by default which is effectively
unlimited in size (2^63). If your system does not support 8-byte
integers, an error will be generated, and you will need to set
"bigint" to 4-byte integers. This restricts your total system size to
about 2 billion atoms or timesteps (2^31).
Note that in src/lmptype.h there are also settings for the MPI data
types associated with the integers that store atom IDs and total
system sizes, which need to be set consistent with the associated C
data types.
In all cases, the size of problem that can be run on a per-processor
basis is limited by 4-byte integer storage to about 2 billion atoms
per processor (2^31), which should not normally be a restriction since
such a problem would have a huge per-processor memory footprint due to
neighbor lists and would run very slowly in terms of CPU
secs/timestep.
:line
2.3 Making LAMMPS with optional packages :h4,link(2_3)