[llvm-dev] GSoC Interested student

Sun Mar 22 10:26:30 PDT 2020

I did not. The issues sections on GH was removed.

________________________________________
From: Hamilton Tobon Mosquera <htobonm at eafit.edu.co>
Sent: Sunday, March 22, 2020 12:21
To: llvm-dev at lists.llvm.org
Cc: Doerfert, Johannes
Subject: Re: [llvm-dev] GSoC Interested student

Hi there Johannes!,

I was checking out the issue (about latency hiding when transferring
memory from host to device) you posted about a week ago, but it's not
there anymore. Did you remove it?.

Thanks.

Hamilton.

On 21/03/20 10:04 p. m., Hamilton Tobon Mosquera via llvm-dev wrote:
> Hi there!,
>
> Right now I'm starting with the project proposed by Johannes here:
> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fissues%2F180&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=oOXfSmxJZCwH5BhydZMwaoO5cXe10NKladeSYh%2F8z%2FA%3D&reserved=0.
>
>
> The first task is identifying OpenMP API calls referred to device memory
> allocation. I first understood how the compiler driver orchestrates the
> process of offloading OpenMP regions to devices, and now I'm looking at
> the step of the pipeline that generates LLVM IR for both host and
> device. I wrote a simple C program that uses OpenMP to map a local array
> to the device main memory. Then I'm looking at the device and host LLVM
> IR representation of this program, but I can't find any runtime call
> referred to device memory allocation. In the host IR I see that the
> array is passed to the outlined function and stored in a register inside
> the outlined function, but there's no memory allocation runtime call.
> And in the device IR the array is passed to the main offloading
> function. Any suggestion or documentation on how that memory transfer is
> achieved?, and how to track its API calls. It might be that I'm not
> using the proper omp directive, so here is C code:
>
>
> #include <omp.h>
> #include <stdio.h>
>
> #define size 1000000
> double a[size];
>
> int main() {
>
>   #pragma omp target map(to: a[0:size])
>   #pragma omp teams distribute
>   for (int i = 0; i < size; ++i) {
>     a[i] = a[i]*(i*i)/2;
>   }
>   return 0;
>
> PD: The command to compile is this: clang -v -save-temps
> -I/path/to/llvm/release/9.x/include -fopenmp
> -fopenmp-targets=nvptx64-nvidia-cuda -Xopenmp-target -march=sm_61
> memory_transfer.c -o memory_transfer
>
> Thank you all.
>
> Hamilton.
>
>
> On 18/03/20 9:21 p. m., Doerfert, Johannes wrote:
>> Hi Hamilton,
>>
>> I personally don't believe the effort to make the IR
>> "parallelism-aware" is worth it right now.
>> What I propose is something else, see for example
>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fyoutu.be%2FzfiHaPaoQPc&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=kdpzZgSvhCA40r57l0KUpYf2Au6P8MkZwGOCDhSL7pw%3D&reserved=0
>> and the OpenMPOpt pass.
>> There are multiple bigger tasks towards better offloading, one of
>> which is described here
>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fissues%2F180&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=oOXfSmxJZCwH5BhydZMwaoO5cXe10NKladeSYh%2F8z%2FA%3D&reserved=0
>> It might be interesting to add the transfer functions used for memory
>> transfer to the OMPKinds.def file so they are known in the
>> OpenMPOpt.cpp pass.
>> Another small task would be to eliminate trivially redundant ones,
>> that is if you have copy X from A to B directly followed by copy X
>> from B to A, remove both.
>>
>> Does this make sense?
>>
>> Cheers,
>>    Johannes
>>
>>
>>
>>
>>
>> ---------------------------------------
>> Johannes Doerfert
>> Researcher
>>
>> Argonne National Laboratory
>> Lemont, IL 60439, USA
>>
>> jdoerfert at anl.gov
>>
>> ________________________________________
>> From: Hamilton Tobon Mosquera <htobonm at eafit.edu.co>
>> Sent: Wednesday, March 18, 2020 19:14
>> To: llvm-dev at lists.llvm.org
>> Cc: Doerfert, Johannes
>> Subject: Re: [llvm-dev] GSoC Interested student
>>
>> Hi there!,
>>
>> I think I'm done with this patch: D76058. If that is everything
>> concerning that, could you please assign me another task.
>>
>> I've been reading about Concurrent Control Flow Graphs, which would
>> be awesome for LLVM because it would be kind of a starting point for
>> optimizations for parallel programs in general. The thing is that it
>> seems more complicated than it is presented in the papers, I think
>> that's why it's not implemented in LLVM yet. So, I think I'll try
>> searching for something else. Nevertheless, don't you think that
>> implementing this is worth the effort?. The papers I'm reading are
>> from 1990s, I don't understand why they aren't widely implemented in
>> big compilers xd.
>>
>> I saw this commit from you:
>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Freviews.llvm.org%2FD29250&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=Q3bYQBzETUGpO%2FMPH4TzWomYDbM593pWRSyPOX%2BTgMs%3D&reserved=0.
>> Is there something I can help with concerning this?.
>>
>> I would like to do contribute to the OpenMP target offloading. Is
>> there anything I can help with?.
>>
>> On 11/03/20 8:51 a. m., Hamilton Tobon Mosquera via llvm-dev wrote:
>>
>> Hi there!,
>>
>> As part of my application process to the next GSoC I'm working on the
>> TODO in OpenMPOpt.cpp line 437:
>>
>>      // TODO: We should validate the declaration agains the types we
>> expect.
>>
>>      Link:
>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fblob%2Fmaster%2Fllvm%2Flib%2FTransforms%2FIPO%2FOpenMPOpt.cpp%23L437&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=t3syDmU4YiIkVVN%2FhQR0vXWOHtGcbLWptel5wRgzsi0%3D&reserved=0<https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fllvm%2Fllvm-project%2Fblob%2Fmaster%2Fllvm%2Flib%2FTransforms%2FIPO%2FOpenMPOpt.cpp%23L437&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=t3syDmU4YiIkVVN%2FhQR0vXWOHtGcbLWptel5wRgzsi0%3D&reserved=0>
>>
>> I have a question. When there is a mismatch in the types (return type
>> or argument types) between the function declaration found and the
>> runtime library function, what should I do?. Show an error or a
>> warning?, continuing with the pass or exiting the program?.
>>
>> Thanks.
>>
>>
>> On 10/03/20 7:12 p. m., Stefanos Baziotis wrote:
>> Hi Hamilton,
>>
>> Thanks for your interest in LLVM!
>>
>> IMHO you have a good start. I'll try to help by CC'ing Johannes. Note
>> that it's difficult for LLVM developers
>> (including GSoC mentors and including Johannes) to keep up with every
>> discussion on llvm-dev.
>> So, you can CC them to make their life easier. :)
>>
>> Johannes, I see a lot of people interested in this project. Maybe a
>> list of starting points, patches etc.
>> could help.
>>
>> Best,
>> Stefanos
>>
>> Στις Τρί, 10 Μαρ 2020 στις 1:04 π.μ., ο/η Hamilton Tobon Mosquera via
>> llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
>> έγραψε:
>> Greetings,
>>
>>
>> I'm an LLVM newcomer interested in participating in the next GSoC under
>> the project "Improve parallelism-aware analyses and optimizations". I've
>> already read "Compiler Optimizations for OpenMP" and "Compiler
>> Optimizations for Parallel Programs" both by Doerfert and Finkel. Also,
>> I've watched their two LLVM meeting developers conferences "Representing
>> parallelism within LLVM" and "Optimizing indirections, using
>> abstractions without ...", so I have some background in the problems
>> they are trying to tackle. Also, I'm close to solve one of the bugs
>> posted in bugzilla, which has given me a broader idea of how the OpenMP
>> pragmas are translated. The bus is this:
>> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugs.llvm.org%2Fshow_bug.cgi%3Fid%3D40253&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=6kv5l3Cq1bdyjUx4WO1OTGtAv6AncQbczEpFvm5MOyk%3D&reserved=0<https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugs.llvm.org%2Fshow_bug.cgi%3Fid%3D40253&data=01%7C01%7Chtobonm%40eafit.edu.co%7C2623ce41dabf4613303e08d7ce0570e7%7C99f7b55e9cbe467b8143919782918afb%7C0&sdata=6kv5l3Cq1bdyjUx4WO1OTGtAv6AncQbczEpFvm5MOyk%3D&reserved=0>.
>>
>>
>> I tried contacting you Johannes but with your Argonne email, I suppose
>> that's why you couldn't answer. Could you tell me more about the
>> project?, what variants do you have?, or what can I focus my application
>> on?. Should I start with what you recommended to Emanuel?.
>>
>> Thank you.
>>
>> _______________________________________________
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