[mpich-discuss] Selecting a specific libfabric fabric/domain

[eric at bit32.net]

Thanks Wesley and Hajime. I tested setting FI_SOCKETS_IFACE=eth1, and it 
looks to work as one would hope, causing libfabric to open up the chosen 
interface.

Eric

On 2/19/19 10:34 AM, Fujita, Hajime via discuss wrote:
> As Wesley mentioned there isn't a way to do it in MPICH, but you may try setting FI_SOCKETS_IFACE to control it at the libfabric level.
> https://ofiwg.github.io/libfabric/v1.7.0/man/fi_sockets.7.html
> 
> I haven't tried this personally, so I'm not sure how it actually works though.
> 
> 
> Thanks,
> Hajime
> 
> On 2/19/19, 10:30 AM, "Wesley Bland via discuss" <discuss at mpich.org> wrote:
> 
>      Hi Eric,
>      
>      There isn’t a way of doing that at the moment with MPICH (I’m not sure if any particular OFI providers have support for this through environment variables or something else). It will open whichever one OFI gives you first (assuming all other capability bits are the same).
>      
>      Thanks,
>      Wesley
>      
>      > On Feb 18, 2019, at 1:40 PM, eric--- via discuss <discuss at mpich.org> wrote:
>      >
>      > Hi there,
>      >
>      > I'm using MPICH with ch4:ofi, and I'm wondering how to select which fabric/domain MPICH will open. I can select the provider with MPIR_CVAR_OFI_USE_PROVIDER, but suppose that the provider has two disjoint fabrics with equivalent capabilities. E.g., suppose I have two ethernet NICs connected to private networks:
>      >
>      > provider: sockets
>      >    fabric: 192.168.1.0/24
>      >    domain: eth0
>      >    version: 2.0
>      >    type: FI_EP_RDM
>      >    protocol: FI_PROTO_SOCK_TCP
>      > provider: sockets
>      >    fabric: 10.0.1.0/24
>      >    domain: eth1
>      >    version: 2.0
>      >    type: FI_EP_RDM
>      >    protocol: FI_PROTO_SOCK_TCP
>      >
>      >
>      > Is there a tunable to pick which will be used?
>      >
>      > Thanks,
>      > Eric
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