TESTING/MATGEN/dlatm7.f(3)

🎀 NAME 🎀

okay so bestie, this is the TESTING/MATGEN/dlatm7.f(3) page from the Library Functions Manual. It's all about DLATM7, the subroutine that computes the entries of D for random test matrices. It's giving MATGEN energy and I'm lowkey obsessed. ✨

✨ SYNOPSIS ✨

🫶 Functions/Subroutines

• subroutine dlatm7 (mode, cond, irsign, idist, iseed, d, n, rank, info) — DLATM7

🦋 Function/Subroutine Documentation 🦋

subroutine dlatm7 (integer mode, double precision cond, integer irsign,
    integer idist, integer, dimension( 4 ) iseed, double precision,
    dimension( * ) d, integer n, integer rank, integer info)

DLATM7

🌸 Purpose 🌸

DLATM7 computes the entries of D as specified by MODE, COND, and IRSIGN. IDIST and ISEED determine the generation of random numbers. DLATM7 is called by DLATMT to generate random test matrices. no cap 💅

💖 The Parameters 💖

• MODE — INTEGER. On entry, this describes how D is to be computed:
  • MODE = 0 means do not change D.
  • MODE = 1 sets D(1)=1 and D(2:RANK)=1.0/COND
  • MODE = 2 sets D(1:RANK-1)=1 and D(RANK)=1.0/COND
  • MODE = 3 sets D(I)=COND**(-(I-1)/(RANK-1)) I=1:RANK
  • MODE = 4 sets D(i)=1 - (i-1)/(N-1)*(1 - 1/COND)
  • MODE = 5 sets D to random numbers in the range ( 1/COND , 1 ) such that their logarithms are uniformly distributed.
  • MODE = 6 set D to random numbers from same distribution as the rest of the matrix.
  • MODE < 0 has the same meaning as ABS(MODE), except that the order of the elements of D is reversed.
  • Thus if MODE is positive, D has entries ranging from 1 to 1/COND; if negative, from 1/COND to 1.
  • Not modified.
• COND — DOUBLE PRECISION. On entry, used as described under MODE above. If used, it must be >= 1. Not modified.
• IRSIGN — INTEGER. On entry, if MODE neither -6, 0 nor 6, determines sign of entries of D:
  • 0 => leave entries of D unchanged
  • 1 => multiply each entry of D by 1 or -1 with probability .5
• IDIST — CHARACTER*1. On entry, IDIST specifies the type of distribution to be used to generate a random matrix:
  • 1 => UNIFORM( 0, 1 )
  • 2 => UNIFORM( -1, 1 )
  • 3 => NORMAL( 0, 1 )
  • Not modified.
  • > tiny note, bestie: the original page labels this as CHARACTER*1 here, while the signature line above says integer idist — I'm just reporting both exactly as they appear. 🫶
• ISEED — INTEGER array, dimension ( 4 ). On entry ISEED specifies the seed of the random number generator. The random number generator uses a linear congruential sequence limited to small integers, and so should produce machine independent random numbers. The values of ISEED are changed on exit, and can be used in the next call to DLATM7 to continue the same random number sequence. Changed on exit.
• D — DOUBLE PRECISION array, dimension ( MIN( M , N ) ). Array to be computed according to MODE, COND, and IRSIGN. May be changed on exit if MODE is nonzero.
• N — INTEGER. Number of entries of D. Not modified.
• RANK — INTEGER. The rank of matrix to be generated for modes 1,2,3 only. D( RANK+1:N ) = 0. Not modified.
• INFO — INTEGER:
  • 0 => normal termination
  • -1 => if MODE not in range -6 to 6
  • -2 => if MODE neither -6, 0 nor 6, and IRSIGN neither 0 nor 1
  • -3 => if MODE neither -6, 0 nor 6 and COND less than 1
  • -4 => if MODE equals 6 or -6 and IDIST not in range 1 to 3
  • -7 => if N negative

💖 Author 💖

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

Definition at line 120 of file dlatm7.f.

🎀 Author 🎀

Generated automatically by Doxygen for LAPACK from the source code.

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okay that's the whole page, bestie. This footer is from LAPACK Version 3.12.0, and it points back to TESTING/MATGEN/dlatm7.f(3). There's no date listed in this footer, just the version and the page name — and honestly, it ate. mwah 💋✨