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How can I use Blas to multiply a real matrix with a complex vector ? When I use functions like ccsrgemv() I get type mismatch errors?
error: argument of type "float *" is incompatible with parameter of type "std::complex<float> *"
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In terms of serial complexity, the matrix-vector multiplication is qualified as a quadratic complexity algorithm (or a bilinear complexity algorithm if the matrix is rectangular).
First, multiply Row 1 of the matrix by Column 1 of the vector. Next, multiply Row 2 of the matrix by Column 1 of the vector. Finally multiply Row 3 of the matrix by Column 1 of the vector.
Matrix-vector product So, if A is an m×n matrix (i.e., with n columns), then the product Ax is defined for n×1 column vectors x. If we let Ax=b, then b is an m×1 column vector. In other words, the number of rows in A (which can be anything) determines the number of rows in the product b.
Use two matrix-vector multiplications (A * (x + iy) = A * x + i A * y). More precisely, consider your complex vector as two entangled real vectors with stride 2. BLAS lets you do this.
UPDATE: actually, I did not notice that you were doing Sparse BLAS. For dgemv my trick works, but for csrgemv it doesn't. I'm afraid you have to maintain real and imaginary part separately.
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