[petsc-users] HashMap Error when populating AIJCUSPARSE matrix

[Barry Smith]

   It is using the hash map system for inserting values which only inserts on the CPU, not on the GPU. So I don't see that it would be moving any data to the GPU until the mat assembly() is done which it never gets to. Hence I have trouble understanding why the GPU has anything to do with the crash. 

   I guess I need to try to reproduce it on a GPU system.

   Barry




> On Jan 18, 2024, at 4:28 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Thu, Jan 18, 2024 at 4:18 PM Yesypenko, Anna <anna at oden.utexas.edu <mailto:anna at oden.utexas.edu>> wrote:
>> Hi Matt, Barry,
>> 
>> Apologies for the extra dependency on scipy. I can replicate the error by calling setValue (i,j,v) in a loop as well.
>> In roughly half of 10 runs, the following script fails because of an error in hashmapijv – the same as my original post.
>> It successfully runs without error the other times.
>> 
>> Barry is right that it's CUDA specific. The script runs fine on the CPU.
>> Do you have any suggestions or example scripts on assigning entries to a AIJCUSPARSE matrix?
> 
> Oh, you definitely do not want to be doing this. I believe you would rather
> 
> 1) Make the CPU matrix and then convert to AIJCUSPARSE. This is efficient.
> 
> 2) Produce the values on the GPU and call
> 
>   https://petsc.org/main/manualpages/Mat/MatSetPreallocationCOO/
>   https://petsc.org/main/manualpages/Mat/MatSetValuesCOO/
> 
>   This is what most people do who are forming matrices directly on the GPU.
> 
> What you are currently doing is incredibly inefficient, and I think accounts for you running out of memory.
> It talks back and forth between the CPU and GPU.
> 
>   Thanks,
> 
>      Matt
> 
>> Here is a minimum snippet that doesn't depend on scipy.
>> ```
>> from petsc4py import PETSc
>> import numpy as np
>> 
>> n = int(5e5); 
>> nnz = 3 * np.ones(n, dtype=np.int32)
>> nnz[0] = nnz[-1] = 2
>> A = PETSc.Mat(comm=PETSc.COMM_WORLD)
>> A.createAIJ(size=[n,n],comm=PETSc.COMM_WORLD,nnz=nnz)
>> A.setType('aijcusparse')
>> 
>> A.setValue(0, 0, 2)
>> A.setValue(0, 1, -1)
>> A.setValue(n-1, n-2, -1)
>> A.setValue(n-1, n-1, 2)
>> 
>> for index in range(1, n - 1):
>>          A.setValue(index, index - 1, -1)
>>          A.setValue(index, index, 2)
>>          A.setValue(index, index + 1, -1)
>> A.assemble()
>> ```
>> If it means anything to you, when the hash error occurs, it is for index 67283 after filling 201851 nonzero values.
>> 
>> Thank you for your help and suggestions!
>> Anna
>> 
>> From: Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>>
>> Sent: Thursday, January 18, 2024 2:35 PM
>> To: Yesypenko, Anna <anna at oden.utexas.edu <mailto:anna at oden.utexas.edu>>
>> Cc: petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov> <petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>>
>> Subject: Re: [petsc-users] HashMap Error when populating AIJCUSPARSE matrix
>>  
>> 
>>    Do you ever get a problem with 'aij` ?   Can you run in a loop with 'aij' to confirm it doesn't fail then?
>> 
>>    
>> 
>>    Barry
>> 
>> 
>>> On Jan 17, 2024, at 4:51 PM, Yesypenko, Anna <anna at oden.utexas.edu <mailto:anna at oden.utexas.edu>> wrote:
>>> 
>>> Dear Petsc users/developers,
>>> 
>>> I'm experiencing a bug when using petsc4py with GPU support. It may be my mistake in how I set up a AIJCUSPARSE matrix.
>>> For larger matrices, I sometimes encounter a error in assigning matrix values; the error is thrown in PetscHMapIJVQuerySet().
>>> Here is a minimum snippet that populates a sparse tridiagonal matrix. 
>>> 
>>> ```
>>> from petsc4py import PETSc
>>> from scipy.sparse import diags
>>> import numpy as np
>>> 
>>> n = int(5e5); 
>>> 
>>> nnz = 3 * np.ones(n, dtype=np.int32); nnz[0] = nnz[-1] = 2
>>> A = PETSc.Mat(comm=PETSc.COMM_WORLD)
>>> A.createAIJ(size=[n,n],comm=PETSc.COMM_WORLD,nnz=nnz)
>>> A.setType('aijcusparse')
>>> tmp = diags([-1,2,-1],[-1,0,+1],shape=(n,n)).tocsr()
>>> A.setValuesCSR(tmp.indptr,tmp.indices,tmp.data)                            ####### this is the line where the error is thrown.
>>> A.assemble()
>>> ```
>>> 
>>> The error trace is below:
>>> ```
>>> File "petsc4py/PETSc/Mat.pyx", line 2603, in petsc4py.PETSc.Mat.setValuesCSR
>>>   File "petsc4py/PETSc/petscmat.pxi", line 1039, in petsc4py.PETSc.matsetvalues_csr
>>>   File "petsc4py/PETSc/petscmat.pxi", line 1032, in petsc4py.PETSc.matsetvalues_ijv
>>> petsc4py.PETSc.Error: error code 76
>>> [0] MatSetValues() at /work/06368/annayesy/ls6/petsc/src/mat/interface/matrix.c:1497
>>> [0] MatSetValues_Seq_Hash() at /work/06368/annayesy/ls6/petsc/include/../src/mat/impls/aij/seq/seqhashmatsetvalues.h:52
>>> [0] PetscHMapIJVQuerySet() at /work/06368/annayesy/ls6/petsc/include/petsc/private/hashmapijv.h:10
>>> [0] Error in external library
>>> [0] [khash] Assertion: `ret >= 0' failed.
>>> ```
>>> 
>>> If I run the same script a handful of times, it will run without errors eventually.
>>> Does anyone have insight on why it is behaving this way? I'm running on a node with 3x NVIDIA A100 PCIE 40GB.
>>> 
>>> Thank you!
>>> Anna
>> 
> 
> 
> --
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>

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