SRC/ctpttf.f(3)

okay so this page is SRC/ctpttf.f(3), straight out of the Library Functions Manual, and it’s all about the LAPACK subroutine ctpttf. 🫶 It’s giving Fortran, it’s giving packed triangles, and we are gonna read every single detail together, bestie. 💅

✨ NAME ✨

SRC/ctpttf.f — the file-name era, iconic, no extra plot. 🎀

🌸 SYNOPSIS 🌸

🧚 Functions/Subroutines

subroutine ctpttf (transr, uplo, n, ap, arf, info)

CTPTTF copies a triangular matrix from the standard packed format (TP) to the rectangular full packed format (TF). Periodt. 💅

🔥 Function/Subroutine Documentation 🔥

💜 subroutine ctpttf (transr, uplo, n, ap, arf, info)

subroutine ctpttf (character transr, character uplo, integer n, complex, dimension( 0: * ) ap, complex, dimension( 0: * ) arf, integer info)

CTPTTF copies a triangular matrix from the standard packed format (TP) to the rectangular full packed format (TF). Yes bestie, same iconic sentence, now in documentation mode. ✨

🎀 Purpose

CTPTTF copies a triangular matrix A from standard packed format (TP) to rectangular full packed format (TF). That’s the assignment. 📝

🍓 Parameters

• TRANSR — is CHARACTER*1. = 'N': ARF in Normal format is wanted; = 'C': ARF in Conjugate-transpose format is wanted. Choose your format era. 💅
• UPLO — is CHARACTER*1. = 'U': A is upper triangular; = 'L': A is lower triangular. Upper or lower, both valid, pick your vibe. 🦋
• N — is INTEGER. The order of the matrix A. N >= 0. No negative-order nonsense here. 🚫
• AP — is COMPLEX array, dimension ( N*(N+1)/2 ). On entry, the upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. Literally packed with care. 🎁
• ARF — is COMPLEX array, dimension ( N*(N+1)/2 ). On exit, the upper or lower triangular matrix A stored in RFP format. For a further discussion see Notes below. 💖
• INFO — is INTEGER. = 0: successful exit; < 0: if INFO = -i, the i-th argument had an illegal value. Bestie, INFO is always watching. 👀

🌸 Author

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

🔥 Further Details

okay so first we’re doing Standard Packed Format when N is even, and the example is N = 6. ✨

      AP is Upper             AP is Lower

   00 01 02 03 04 05       00
      11 12 13 14 15       10 11
         22 23 24 25       20 21 22
            33 34 35       30 31 32 33
               44 45       40 41 42 43 44
                  55       50 51 52 53 54 55

Let TRANSR = 'N'. RFP holds AP as follows: for UPLO = 'U' the upper trapezoid A(0:5,0:2) consists of the last three columns of AP upper. The lower triangle A(4:6,0:2) consists of conjugate-transpose of the first three columns of AP upper. For UPLO = 'L' the lower trapezoid A(1:6,0:2) consists of the first three columns of AP lower. The upper triangle A(0:2,0:2) consists of conjugate-transpose of the last three columns of AP lower. To denote conjugate we place -- above the element. This covers the case N even and TRANSR = 'N'. 💅

         RFP A                   RFP A

                                -- -- --
        03 04 05                33 43 53
                                   -- --
        13 14 15                00 44 54
                                      --
        23 24 25                10 11 55

        33 34 35                20 21 22
        --
        00 44 45                30 31 32
        -- --
        01 11 55                40 41 42
        -- -- --
        02 12 22                50 51 52

Now let TRANSR = 'C'. RFP A in both UPLO cases is just the conjugate-transpose of RFP A above. One therefore gets: 🦋

           RFP A                   RFP A

     -- -- -- --                -- -- -- -- -- --
     03 13 23 33 00 01 02    33 00 10 20 30 40 50
     -- -- -- -- --                -- -- -- -- --
     04 14 24 34 44 11 12    43 44 11 21 31 41 51
     -- -- -- -- -- --                -- -- -- --
     05 15 25 35 45 55 22    53 54 55 22 32 42 52

Next up: Standard Packed Format when N is odd, example N = 5. 🎀

     AP is Upper                 AP is Lower

   00 01 02 03 04              00
      11 12 13 14              10 11
         22 23 24              20 21 22
            33 34              30 31 32 33
               44              40 41 42 43 44

Let TRANSR = 'N'. RFP holds AP as follows: for UPLO = 'U' the upper trapezoid A(0:4,0:2) consists of the last three columns of AP upper. The lower triangle A(3:4,0:1) consists of conjugate-transpose of the first two columns of AP upper. For UPLO = 'L' the lower trapezoid A(0:4,0:2) consists of the first three columns of AP lower. The upper triangle A(0:1,1:2) consists of conjugate-transpose of the last two columns of AP lower. To denote conjugate we place -- above the element. This covers the case N odd and TRANSR = 'N'. 🌈

         RFP A                   RFP A

                                   -- --
        02 03 04                00 33 43
                                      --
        12 13 14                10 11 44

        22 23 24                20 21 22
        --
        00 33 34                30 31 32
        -- --
        01 11 44                40 41 42

Now let TRANSR = 'C'. RFP A in both UPLO cases is just the conjugate-transpose of RFP A above. One therefore gets: 💖

           RFP A                   RFP A

     -- -- --                   -- -- -- -- -- --
     02 12 22 00 01             00 10 20 30 40 50
     -- -- -- --                   -- -- -- -- --
     03 13 23 33 11             33 11 21 31 41 51
     -- -- -- -- --                   -- -- -- --
     04 14 24 34 44             43 44 22 32 42 52

Definition at line 206 of file ctpttf.f.

👑 Author

Generated automatically by Doxygen for LAPACK from the source code. 🤖

---

okay bestie, that’s the whole page — footer-coded as LAPACK, Version 3.12.0, source SRC/ctpttf.f(3), and there’s no date line to speak of, so we’re not inventing one. 💖✨🎀