From 7f310b42d20952e3cc1f26bf66833b7bf9089ead Mon Sep 17 00:00:00 2001
From: Tim Holy <tim.holy@gmail.com>
Date: Mon, 13 Oct 2025 07:54:08 -0500
Subject: [PATCH] Add working & efficient `fill!(A, 0)`

---
 src/SparseMatrixCSR.jl  | 11 ++++++++---
 test/SparseMatrixCSR.jl |  4 ++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/SparseMatrixCSR.jl b/src/SparseMatrixCSR.jl
index 66a0df4..d145d09 100644
--- a/src/SparseMatrixCSR.jl
+++ b/src/SparseMatrixCSR.jl
@@ -37,7 +37,7 @@ struct SparseMatrixCSR{Bi,Tv,Ti} <: AbstractSparseMatrix{Tv,Ti}
       throw(ArgumentError("$str must be $r, got $k"))
     m < 0 && throwsz("m",">=0",m)
     n < 0 && throwsz("n",">=0", n)
-    length(rowptr) != m+1 && throwsz("lengh(rowptr)",m+1,length(rowptr))
+    length(rowptr) != m+1 && throwsz("length(rowptr)",m+1,length(rowptr))
     rowptr[end]-Bi != length(nzval) && throwsz("rowptr[end]-Bi",rowptr[m+1]-Bi, length(nzval))
     new{Bi,Tv,Ti}(Int(m), Int(n), rowptr, colval, nzval)
   end
@@ -58,14 +58,14 @@ end
 """
     SparseMatrixCSR(a::SparseMatrixCSC}
 
-Build a 1-based `SparseMatrixCSR` from a `SparseMatrixCSC`. 
+Build a 1-based `SparseMatrixCSR` from a `SparseMatrixCSC`.
 """
 SparseMatrixCSR(a::SparseMatrixCSC) = SparseMatrixCSR(transpose(sparse(transpose(a))))
 
 """
     SparseMatrixCSR(a::AbstractMatrix}
 
-Build a 1-based `SparseMatrixCSR` from an `AbstractMatrix`. 
+Build a 1-based `SparseMatrixCSR` from an `AbstractMatrix`.
 """
 SparseMatrixCSR(a::AbstractMatrix) = SparseMatrixCSR(sparse(a))
 
@@ -141,6 +141,11 @@ function LinearAlgebra.fillstored!(a::SparseMatrixCSR,v)
   a
 end
 
+function Base.fill!(a::SparseMatrixCSR,v)
+  iszero(v) && return LinearAlgebra.fillstored!(a,v)
+  invoke(Base.fill!,Tuple{AbstractMatrix,typeof(v)},a,v)
+end
+
 function LinearAlgebra.rmul!(a::SparseMatrixCSR,v::Number)
   rmul!(a.nzval,v)
   a
diff --git a/test/SparseMatrixCSR.jl b/test/SparseMatrixCSR.jl
index 47bad8d..69e9709 100644
--- a/test/SparseMatrixCSR.jl
+++ b/test/SparseMatrixCSR.jl
@@ -118,6 +118,10 @@ function test_csr(Bi,Tv,Ti)
   mul!(z,CSC,x)
   @test y ≈ z
 
+  @test_throws ArgumentError fill!(CSR2,3.33)
+  fill!(CSR2, 0)
+  @test all(iszero, CSR2)
+
   # test constructors
   @test CSR == SparseMatrixCSR(CSC)
   @test CSR == SparseMatrixCSR(Matrix(CSC))