Error when using Sparse matrix with Gurobi variables

Answered

Sagnik Basumallik

August 16, 2020 21:10

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Hi,

I have a dense matrix H which I have transformed into a sparse matrix.

from scipy import sparse
sH = sparse.csr_matrix(H)

I have a D matrix which is an identity matrix with Gurobi variables in the diagonal <gurobi.Var z[i,j]>.

I try to multiple the following:

r = np.dot(np.transpose(sH),D)

This is the error I am getting: ( I do not get this error if my matrices are not sparse)

---------------------------------------------------------------------------
TypeError                                 
Traceback (most recent call last)
var.pxi in gurobipy.Var.__rmul__()
TypeError: float() argument must be a string or a number, not 'csc_matrix'
During handling of the above exception, another exception occurred:
TypeError                                 Traceback (most recent call last)
linexpr.pxi in gurobipy.LinExpr.__imul__()
TypeError: float() argument must be a string or a number, not 'csc_matrix'
During handling of the above exception, another exception occurred:
GurobiError                               Traceback (most recent call last)
<ipython-input-74-48094dbb4ef2> in <module>()
----> 1 r = np.dot(np.transpose(sH),D)
<__array_function__ internals> in dot(*args, **kwargs)
var.pxi in gurobipy.Var.__rmul__()
linexpr.pxi in gurobipy.LinExpr.__imul__()
linexpr.pxi in gurobipy.LinExpr.__mul__()
linexpr.pxi in gurobipy.LinExpr._mul()
GurobiError: Invalid argument to LinExpr multiplication

 

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• Official comment

  

  Simranjit Kaur

  • Gurobi Staff

  December 06, 2024 00:42

  This post is more than three years old. Some information may not be up to date. For current information, please check the Gurobi Documentation or Knowledge Base. If you need more help, please create a new post in the community forum. Or why not try our AI Gurobot?.
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  Jaromił Najman

  • Gurobi Staff

  September 02, 2020 07:35

  Hi Sagnik,

  Could you provide a minimal working example producing the error you posted?
  
  In case, you were able to solve the problem, could you provide the solution of how you achieved it?
  
  Best regards,
  Jaromił

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• 

  Brannon King

  November 07, 2023 23:43

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  This question is old, but so as it has an answer: you can't use numpy functions on scipy sparse objects. The transpose should be sH.T and the dot product should be done via the @ operator: sH @ D . 

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