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// =============================================================================
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// === spqr_cpack ==============================================================
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// =============================================================================
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// spqr_cpack copies the C matrix from the frontal matrix F and
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// stores it in packed form. F can be overwritten with C (the pack can occur
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// in-place), but in that case, the R and H matrices are destroyed.
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// In this example, m = 5, n = 6, npiv = 2, and rank = 2 (the number of good
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// pivot columns found; equivalently, the number of rows in the R block). The
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// number of columns in C is cn = n-npiv. The number of rows is
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// cm = MIN (m-rank,cn). In this example, MIN (m-rank,cn) = 3.
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// . . c c c c <- rank = 2
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// In the next example below, m = 8 instead. Note that
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// cm = MIN (m-rank,cn) = 4.
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// . . c c c c <- rank = 2
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template <typename Entry> Int spqr_cpack // returns # of rows in C
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// input, not modified
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Int m, // # of rows in F
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Int n, // # of columns in F
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Int npiv, // number of pivotal columns in F
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Int rank, // the C block starts at F (rank,npiv)
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// input, not modified unless the pack occurs in-place
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Entry *F, // m-by-n frontal matrix in column-major order
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// output, contents not defined on input
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Entry *C // packed columns of C, of size cm-by-cn in upper
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// -------------------------------------------------------------------------
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// -------------------------------------------------------------------------
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ASSERT (m >= 0 && n >= 0 && npiv >= 0 && npiv <= n) ;
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ASSERT (rank >= 0 && rank <= MIN (m,npiv)) ;
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cn = n - npiv ; // number of columns of C
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cm = MIN (m-rank, cn) ; // number of rows of C
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if (cm <= 0 || cn <= 0)
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return (0) ; // nothing to do
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ASSERT (C != NULL && F != NULL) ;
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ASSERT (C <= F // C can be packed in-place, in F
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|| C >= F + m*n) ; // or C must appear after F
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F += INDEX (rank,npiv,m) ; // C starts at F (rank,npiv)
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// -------------------------------------------------------------------------
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// pack the upper triangular part of C
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// -------------------------------------------------------------------------
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for (k = 0 ; k < cm ; k++)
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for (i = 0 ; i <= k ; i++)
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F += m ; // advance to the next column of F
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// -------------------------------------------------------------------------
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// pack the rectangular part of C
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// -------------------------------------------------------------------------
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for (i = 0 ; i < cm ; i++)
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F += m ; // advance to the next column of F
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PR (("Cpack rank %ld cm %ld cn %ld\n", rank, cm, cn)) ;
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return (cm) ; // return # of rows in C
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// =============================================================================
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template Int spqr_cpack <double> // returns # of rows in C
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// input, not modified
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Int m, // # of rows in F
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Int n, // # of columns in F
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Int npiv, // number of pivotal columns in F
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Int rank, // the C block starts at F (rank,npiv)
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// input, not modified unless the pack occurs in-place
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double *F, // m-by-n frontal matrix in column-major order
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// output, contents not defined on input
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double *C // packed columns of C, of size cm-by-cn in upper
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// =============================================================================
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template Int spqr_cpack <Complex> // returns # of rows in C
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// input, not modified
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Int m, // # of rows in F
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Int n, // # of columns in F
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Int npiv, // number of pivotal columns in F
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Int rank, // the C block starts at F (rank,npiv)
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// input, not modified unless the pack occurs in-place
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Complex *F, // m-by-n frontal matrix in column-major order
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// output, contents not defined on input
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Complex *C // packed columns of C, of size cm-by-cn in upper
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SPQR/Source/spqr_cpack.cpp
