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corrected inverse_exact #444

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corrected inverse_exact #444

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30 changes: 20 additions & 10 deletions ext/nmatrix/math.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -385,10 +385,11 @@ namespace nm {
rb_raise(nm_eNotInvertibleError,
"matrix must have non-zero determinant to be invertible (not getting this error does not mean matrix is invertible if you're dealing with floating points)");
}
DType index= A[0];
B[0] = A[lda+1] / det;
B[1] = -A[1] / det;
B[ldb] = -A[lda] / det;
B[ldb+1] = -A[0] / det;
B[ldb+1] = index/ det;

} else if (M == 3) {
// Calculate the exact determinant.
Expand All @@ -398,16 +399,24 @@ namespace nm {
rb_raise(nm_eNotInvertibleError,
"matrix must have non-zero determinant to be invertible (not getting this error does not mean matrix is invertible if you're dealing with floating points)");
}

DType a1= A[0];
DType b1= A[1];
DType c1= A[2];
DType d1= A[lda];
DType e1= A[lda+1];
DType f1= A[lda+2];
DType g1= A[2*lda];
DType h1= A[2*lda+1];
DType i1= A[2*lda+2];
B[0] = ( A[lda+1] * A[2*lda+2] - A[lda+2] * A[2*lda+1]) / det; // A = ei - fh
B[1] = (- A[1] * A[2*lda+2] + A[2] * A[2*lda+1]) / det; // D = -bi + ch
B[2] = ( A[1] * A[lda+2] - A[2] * A[lda+1]) / det; // G = bf - ce
B[ldb] = (- A[lda] * A[2*lda+2] + A[lda+2] * A[2*lda]) / det; // B = -di + fg
B[ldb+1] = ( A[0] * A[2*lda+2] - A[2] * A[2*lda]) / det; // E = ai - cg
B[ldb+2] = (- A[0] * A[lda+2] + A[2] * A[lda]) / det; // H = -af + cd
B[2*ldb] = ( A[lda] * A[2*lda+1] - A[lda+1] * A[2*lda]) / det; // C = dh - eg
B[2*ldb+1]= ( -A[0] * A[2*lda+1] + A[1] * A[2*lda]) / det; // F = -ah + bg
B[2*ldb+2]= ( A[0] * A[lda+1] - A[1] * A[lda]) / det; // I = ae - bd
B[1] = (- A[1] * i1 + A[2] * h1) / det; // D = -bi + ch
B[2] = ( b1 * f1 - c1 * e1) / det; // G = bf - ce
B[ldb] = (- d1 * i1 + f1 * g1) / det; // B = -di + fg
B[ldb+1] = ( a1 * i1 - c1 * g1) / det; // E = ai - cg
B[ldb+2] = (- a1 * f1 + c1 * d1) / det; // H = -af + cd
B[2*ldb] = ( d1 * h1 - e1 * g1) / det; // C = dh - eg
B[2*ldb+1]= ( -a1 * h1 + b1 * g1) / det; // F = -ah + bg
B[2*ldb+2]= ( a1 * e1 - b1 * d1) / det; // I = ae - bd
} else if (M == 1) {
B[0] = 1 / A[0];
} else {
Expand Down Expand Up @@ -1125,3 +1134,4 @@ void nm_math_transpose_generic(const size_t M, const size_t N, const void* A, co


} // end of extern "C" block

9 changes: 8 additions & 1 deletion lib/nmatrix/math.rb
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Expand Up @@ -80,7 +80,13 @@ def invert!
raise(DataTypeError, "Cannot invert an integer matrix in-place") if self.integer_dtype?

#No internal implementation of getri, so use this other function
__inverse__(self, true)
n= self.shape[0]
if n<4
__inverse_exact__(self, n,n)
else
__inverse__(self,true)

end
end

#
Expand Down Expand Up @@ -1102,3 +1108,4 @@ def dtype_for_floor_or_ceil
end
end
end