Error in creating a unit diagonal sparse matrix

[binxiangni]

Error occurred when creating a unit diagonal sparse matrix whose size is the same as another sparse matrix's. The error message is:

#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]

using namespace Rcpp;
using namespace arma;

//[[Rcpp::export]]
sp_mat speye_(sp_mat X) {
  // Create a unit diagonal sparse matrix whose size is the same as X's.  
  return speye(size(X)); 
}

/*** R
library(Matrix)
dtT <- new("dtTMatrix", x= c(3,7), i= 0:1, j=3:2, Dim= as.integer(c(4,4)))
speye_(dtT)

dgT <- new("dgTMatrix",
          i = as.integer(c(1,1,0,3,3)),
          j = as.integer(c(2,2,4,0,0)), x=10*1:5, Dim=4:5)
speye_(dgT)

# Output
# > speye_(dtT)
# 4 x 4 sparse Matrix of class "dgCMatrix"
#            
# [1,] 1 . . .
# [2,] . 1 . .
# [3,] . . 1 .
# [4,] . . . 1
# 
# > speye_(dgT)
# 4 x 5 sparse Matrix of class "dgCMatrix"
# Error in validObject(x) : 
#  invalid class “dgCMatrix” object: slot p must be non-decreasing

*/

[thirdwing]

Actually, this has nothing to do with your code in this GSOC. This is a corner case we didn't think about.

Another smaller example to reproduce this error:

#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]
//
using namespace Rcpp;
using namespace arma;

//[[Rcpp::export]]
sp_mat test() {
  return speye(4, 5);
}

/*
> Rcpp::sourceCpp("test.cpp")
> library(Matrix)
> test()
4 x 5 sparse Matrix of class "dgCMatrix"
Error in validObject(x) : 
  invalid class “dgCMatrix” object: slot p must be non-decreasing
*/

[binxiangni]

But after loading the package "Matrix", your error message disappeared while mine came out.

#include <RcppArmadillo.h>
// [[Rcpp::depends(RcppArmadillo)]]
//
using namespace Rcpp;
using namespace arma;

//[[Rcpp::export]]
sp_mat test() {
  return speye(4, 5);
}

/*
> Rcpp::sourceCpp("test.cpp")
> test()
Error in getClass("dgCMatrix") : “dgCMatrix” is not a defined class 
> library(Matrix)
> test()
Error in validObject(x) : 
  invalid class “dgCMatrix” object: slot p must be non-decreasing
*/

Your example might prove there might not be a problem in as<>(), but the problem might exist in wrap().

[thirdwing]

I have updated my error message. The problem is in wrap.

[thirdwing]

I think we met the error because the p slot in dgCMatrix from Matrix pkg is slightly different from the col_ptrs in arma.