Team:EPF-Lausanne/Modeling/RunSimulation

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=How to run a complete simulation=
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=Theory=
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==Theory==
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The .pdb is generated from X-ray diffraction crystallography. This process requires a crystal of the protein, which occurs only at low temperature (~5°K). Taking this in consideration, we have to go through different steps to bring our protein to lab conditions.
The .pdb is generated from X-ray diffraction crystallography. This process requires a crystal of the protein, which occurs only at low temperature (~5°K). Taking this in consideration, we have to go through different steps to bring our protein to lab conditions.
'''Please refer to the page on [[Team:EPF-Lausanne/Modeling/NamdConf|.conf parameters]] to see how to perform these steps in namd.'''
'''Please refer to the page on [[Team:EPF-Lausanne/Modeling/NamdConf|.conf parameters]] to see how to perform these steps in namd.'''
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===Initial minimization===
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==Initial minimization==
We start with a few minimization rounds, to reach a minimum in the sense of potential energy.
We start with a few minimization rounds, to reach a minimum in the sense of potential energy.
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===Heating===
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==Heating==
When the protein is stable, we have to add heat (kinetic energy) to reach a higher temperature (~300°K). We have to take a special care not to add heat too fast, which would result in protein burst and explosion of our system.
When the protein is stable, we have to add heat (kinetic energy) to reach a higher temperature (~300°K). We have to take a special care not to add heat too fast, which would result in protein burst and explosion of our system.
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===First NPT===
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==First NPT==
This is a relaxation step, with the number of atoms N, the pressure P and the temperature T all kept constant (NPT step). This is a kind of homogenization of the distribution of atoms inside our box.
This is a relaxation step, with the number of atoms N, the pressure P and the temperature T all kept constant (NPT step). This is a kind of homogenization of the distribution of atoms inside our box.
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===NVT===
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==NVT==
This is also a relaxation step, with atom number, volume and temperature constant.
This is also a relaxation step, with atom number, volume and temperature constant.
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===Second NPT===
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==Second NPT==
Now we perform another relaxation NPT to reach lab conditions.
Now we perform another relaxation NPT to reach lab conditions.
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===Final NPT===
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==Final NPT==
This is the final NPT, which last much longer and gives us the ouput of the simulation.
This is the final NPT, which last much longer and gives us the ouput of the simulation.
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==.conf file==
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=Launch the simulation=
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===Simulation parameters===
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==On a single processor==
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Here is a safe command. It will send the output (> outpu...) to a file and be run in the background (&).
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:''namd2 CONFIG_FILE.conf > output/namd_log &''
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For the Constant Pressure Control (so during the variable volume period):
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==On a cluster==
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: useGroupPressure      yes ;   # needed for rigidBonds
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This is performed using a library that will split the process between nodes.
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: useFlexibleCell      no   # no for water box, yes for membrane
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===updalpe1pc9.epfl.ch (UPDALPE1PC9)===
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: useConstantArea      no   # idem
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The path to the binary has to be localized using: ''which namd2''. The option +p4 specifies how many procs we are using (don't ue more than 4 on this cluster!). The rest is similar to single processor launch. We use this computer to visualize or perform small stabilization.
 +
charmrun /usr/local/bin/namd2 +p4 ++local 2v0w_hydr_wb_eq_try.conf > ./output_eq2/namd_log &
 +
===updalpe1linuxsrv1.epfl.ch (master.cluster)===
 +
This is the real cluster.
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===Initial minimization===
 
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This is quite easy to achieve, as NAMD has a specific keyword to run a simulation:
 
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: minimize #number of minimization steps
 
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In more details:
 
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<br>Run one step to get into scripting mode
 
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: minimize 0
 
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Turn off until later
 
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: langevinPiston off
 
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Minimization
 
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: reinitvels          5      #reinitialization of all velocities
 
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: minimize            100    #no need to run
 
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: output min
 
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===Heating===
 
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We tried different protocol, but this one is the best:
 
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: reassignTemp        $temp_step ;      # starting temp
 
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: reassignIncr        $temp_step ;      # temp increment
 
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: reassignHold        300 ;            # final temp
 
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: reassignFreq        100 ;            # num timesteps to temp incr.
 
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For this first step, we wanted a continous growing of temperature, so we used: (here for example from 5 to 30K)
 
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: for {set i 5} {$i < 30} {incr i 5} {
 
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: set temperature $i
 
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: langevinTemp $temperature
 
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: run 30}
 
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: output heat
 

Revision as of 09:48, 14 August 2009



Contents

Theory

The .pdb is generated from X-ray diffraction crystallography. This process requires a crystal of the protein, which occurs only at low temperature (~5°K). Taking this in consideration, we have to go through different steps to bring our protein to lab conditions. Please refer to the page on .conf parameters to see how to perform these steps in namd.

Initial minimization

We start with a few minimization rounds, to reach a minimum in the sense of potential energy.

Heating

When the protein is stable, we have to add heat (kinetic energy) to reach a higher temperature (~300°K). We have to take a special care not to add heat too fast, which would result in protein burst and explosion of our system.

First NPT

This is a relaxation step, with the number of atoms N, the pressure P and the temperature T all kept constant (NPT step). This is a kind of homogenization of the distribution of atoms inside our box.

NVT

This is also a relaxation step, with atom number, volume and temperature constant.

Second NPT

Now we perform another relaxation NPT to reach lab conditions.

Final NPT

This is the final NPT, which last much longer and gives us the ouput of the simulation.

Launch the simulation

On a single processor

Here is a safe command. It will send the output (> outpu...) to a file and be run in the background (&).

namd2 CONFIG_FILE.conf > output/namd_log &

On a cluster

This is performed using a library that will split the process between nodes.

updalpe1pc9.epfl.ch (UPDALPE1PC9)

The path to the binary has to be localized using: which namd2. The option +p4 specifies how many procs we are using (don't ue more than 4 on this cluster!). The rest is similar to single processor launch. We use this computer to visualize or perform small stabilization. charmrun /usr/local/bin/namd2 +p4 ++local 2v0w_hydr_wb_eq_try.conf > ./output_eq2/namd_log &

updalpe1linuxsrv1.epfl.ch (master.cluster)

This is the real cluster.




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