# Re: [Wien] NMATMAX

```   0K ! Now it is clear !
Thank you very much !
All the best,
Luis```
```

2016-07-12 15:35 GMT-03:00 Maciej Polak <maciej.po...@pwr.edu.pl>:

> Everything is OK, that only means that you have a complex calculation, in
> which case the NMATMAX is in addition reduced by sqrt(2), so you have
> 13000*sqrt(36/2)=55154. You should read the users guide, its all there
> (page 213).
> Try 64 cores.
>
> Best regards
>
> Maciej Polak
>
>
>
> On 07/12/2016 08:26 PM, Luis Ogando wrote:
>
> Dear Polak,
>
>    Thank you for your response.
>    In fact, I am using only one k-point with in a 36 processors MPI
> calculation. In this case, I should have the matrix size limited to 13000
> (NMATMAX) x sqrt(36) = 78000, but I am getting "MATRIX SIZE" = 55150. What
> am I still missing ? Is NMATMAX defined in another place ?
>    Thank you again.
>    All the best,
>              Luis
>
>
>
> 2016-07-12 15:11 GMT-03:00 Maciej Polak <maciej.po...@pwr.edu.pl>:
>
>> The NMATMAX you have defined in your param.inc is the maximum size for a
>> non mpi parallel calculation. If you use MPI, then the NMATMAX will be
>> automatically increased by sqrt(nmpi). So if you want to increase your
>> matrix size, the best way is to use mpi parallel execution. Simply
>> increasing NMATMAX and recompiling lapw1 and then running it without mpi
>> may lead to unrealistically high computational time.
>> And yes, the NMATMAX is really limiting the effective the RKmax, as you
>> need more matrix elements to represent a bigger basis set.
>>
>> Best regards
>>
>> Maciej Polak
>>
>>
>> On 07/12/2016 07:53 PM, Luis Ogando wrote:
>>
>> Dear Wien2k community,
>>
>>    I am calculating a compound with H atoms. Due to this, I used RKmax =
>> 3.0 as recommended in the Wien2k homepage.
>>    The calculating run without a problem, but I got :
>>
>> :WARN :      WARNING: RKmax reduced due to NMATMAX
>>
>>    In \$WIENROOT/SRC_lpaw1/param.inc I have NMATMAX=13000 and, to my
>> surprise, I also have :
>>
>> :RKM  : MATRIX SIZE 55150LOs: 295  RKM= 2.38  WEIGHT= 1.00  PGR:
>>
>> when I was expecting MATRIX SIZE <= NMATMAX
>>    I would like to get an effective RKmax=3.0 for testing convergence and
>> to get it I was thinking in changing NMATMAX in
>> \$WIENROOT/SRC_lpaw1/param.inc and recompiling the SRC_lapw1 directory.
>>    Well, as I am not sure if NMATMAX is really limiting the effective
>> RKmax, I would like to know what I misunderstood and what is the correct
>> procedure to increase the effective RKmax.
>>    Thank you for your attention !
>>    All the best,
>>                       Luis
>>
>>
>>
>>
>>
>>
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>
>
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