Question: I am trying to calculate the eigenspectrum for a number of large matrices using Scalapack, but rather than distribute each matrix across all 32 processes. I'd rather distribute each matrix across 4 processes and calculate 8 matrices in parallel. I know how to subdivide an MPI Grid using MPI\_Comm\_split, but I it seems Scalapack doesn't take custom communicators. Instead it seems to use a BLACS grid rooted in PVM. 

How can I implement this subdivision in Scalapack?

Answer: 
I have an addendum to Justin Gould's answer. With "IF Always" you will break purge requests from Azure. Fortunately, they have a specific User-Agent so you can match on that.

In addition, it will break HTTP → HTTPS redirection if you do that with another rule. Verizon won't let you match on "Request Scheme" to filter out those requests so you have to be sneaky and match on X-Forwarded-Proto.

Instead of "IF" "Always", you'll want to set:

* "IF" → "Request Header Regex" → Name: "User-Agent" → "Does Not Match" → "ECPurge/\*" → Ignore Case: *checked*
* "AND IF" → "Request Header Literal" → Name: "X-Forwarded-Proto" → "Does Not Match" → "http" → Ignore Case: *checked*
* Then, follow the rest of Justin's instructions.

Reference: <https://github.com/Azure/azure-cli/issues/6722>
So it seems like your issue is:

> 
> these requests for files are all failing with a 404 because I guess the rewrite rule is acting on these as well
> 
> 
> 

And if your assumption is correct, it seems like you would need to request files using their relative path instead of the fully qualified one. Have you tried it? 

For example, the resource you are trying to get lives here:

```
 http://example.com/resource/myresource.pdf

```

but when you use this path you get redirected to something like:

```
 http://example.com/resource/index.html/myresource.pdf

```

...so when referencing the resource if you use a relative path it would look something like this

```
<a href="/resource/myresource.pdf">my resource</a>

```

If I misunderstood your question or issue, or this doesnt solve your problem- add the full error you receive in the developer console (F12).. including what the url should be and what its transforming to when you encounter the issue.