topic rotg and rot example in IntelĀ® oneAPI Math Kernel Library & IntelĀ® Math Kernel Library
https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/rotg-and-rot-example/m-p/773450#M811
Hello, <BR /><BR />Can anyone point me to examples for using BLAS rotg together with rot? I think I understand rotg but not rot (applying the transformation) so well.<BR /><BR />Basically I have a matrix A and its QR in compact LAPACK form. Now I add a row of ones to A and need to eliminate them. So the R would be e.g. 4x4 -> 5x4<BR /><BR />x x x x<BR />0 x x x<BR />0 0 x x<BR />0 0 0 x<BR />1 1 1 1<BR /><BR />use rotg to rotate x_11 with 1, get r1, z1, c1, s1<BR />use rotg to rotate x_22 with 1, get r2, z2, c2, s2<BR />use rotg to rotate x_33 with 1, get r3, z3, c3, s3<BR />use rotg to rotate x_44 with 1, get r4, z4, c4, s4<BR /><BR />At this point I need to apply the rotation transformation on a new vector c of dimension e.g. 5x1 using rot and this is what is not clear to me. The vector c is in the context of solving an overdetermined linear system Ax=b process where I do:<BR /><BR />1) dormqr apply previously existing QR to b i.e. Q'*b=c<BR />2) apply rotations using rot to c and get H1*H2*H3*H4*c=c' ... how to do this? any way to bundle them all together?<BR />3) do the usual right substitution R*x = c'<BR /><BR />Thanks in advance,<BR />Best regards,<BR />Giovanni<BR /><BR /><BR /><BR />Thu, 12 Apr 2012 15:28:00 GMTAzua_Garcia__Giovann2012-04-12T15:28:00Zrotg and rot example
https://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/rotg-and-rot-example/m-p/773450#M811
Hello, <BR /><BR />Can anyone point me to examples for using BLAS rotg together with rot? I think I understand rotg but not rot (applying the transformation) so well.<BR /><BR />Basically I have a matrix A and its QR in compact LAPACK form. Now I add a row of ones to A and need to eliminate them. So the R would be e.g. 4x4 -> 5x4<BR /><BR />x x x x<BR />0 x x x<BR />0 0 x x<BR />0 0 0 x<BR />1 1 1 1<BR /><BR />use rotg to rotate x_11 with 1, get r1, z1, c1, s1<BR />use rotg to rotate x_22 with 1, get r2, z2, c2, s2<BR />use rotg to rotate x_33 with 1, get r3, z3, c3, s3<BR />use rotg to rotate x_44 with 1, get r4, z4, c4, s4<BR /><BR />At this point I need to apply the rotation transformation on a new vector c of dimension e.g. 5x1 using rot and this is what is not clear to me. The vector c is in the context of solving an overdetermined linear system Ax=b process where I do:<BR /><BR />1) dormqr apply previously existing QR to b i.e. Q'*b=c<BR />2) apply rotations using rot to c and get H1*H2*H3*H4*c=c' ... how to do this? any way to bundle them all together?<BR />3) do the usual right substitution R*x = c'<BR /><BR />Thanks in advance,<BR />Best regards,<BR />Giovanni<BR /><BR /><BR /><BR />Thu, 12 Apr 2012 15:28:00 GMThttps://community.intel.com/t5/Intel-oneAPI-Math-Kernel-Library/rotg-and-rot-example/m-p/773450#M811Azua_Garcia__Giovann2012-04-12T15:28:00Z