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---
:name: dlae2
:md5sum: 6634a79d68e158282cf44e0eded12a8d
:category: :subroutine
:arguments:
- a:
:type: doublereal
:intent: input
- b:
:type: doublereal
:intent: input
- c:
:type: doublereal
:intent: input
- rt1:
:type: doublereal
:intent: output
- rt2:
:type: doublereal
:intent: output
:substitutions: {}
:fortran_help: " SUBROUTINE DLAE2( A, B, C, RT1, RT2 )\n\n\
* Purpose\n\
* =======\n\
*\n\
* DLAE2 computes the eigenvalues of a 2-by-2 symmetric matrix\n\
* [ A B ]\n\
* [ B C ].\n\
* On return, RT1 is the eigenvalue of larger absolute value, and RT2\n\
* is the eigenvalue of smaller absolute value.\n\
*\n\n\
* Arguments\n\
* =========\n\
*\n\
* A (input) DOUBLE PRECISION\n\
* The (1,1) element of the 2-by-2 matrix.\n\
*\n\
* B (input) DOUBLE PRECISION\n\
* The (1,2) and (2,1) elements of the 2-by-2 matrix.\n\
*\n\
* C (input) DOUBLE PRECISION\n\
* The (2,2) element of the 2-by-2 matrix.\n\
*\n\
* RT1 (output) DOUBLE PRECISION\n\
* The eigenvalue of larger absolute value.\n\
*\n\
* RT2 (output) DOUBLE PRECISION\n\
* The eigenvalue of smaller absolute value.\n\
*\n\n\
* Further Details\n\
* ===============\n\
*\n\
* RT1 is accurate to a few ulps barring over/underflow.\n\
*\n\
* RT2 may be inaccurate if there is massive cancellation in the\n\
* determinant A*C-B*B; higher precision or correctly rounded or\n\
* correctly truncated arithmetic would be needed to compute RT2\n\
* accurately in all cases.\n\
*\n\
* Overflow is possible only if RT1 is within a factor of 5 of overflow.\n\
* Underflow is harmless if the input data is 0 or exceeds\n\
* underflow_threshold / macheps.\n\
*\n\
* =====================================================================\n\
*\n"
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