`zsyr2k:`procedure`xSYR2K`performs one of the symmetric rank 2k operations`C := alpha*A*B' + beta*C`or`C := alpha*B'*A + beta*C`.`ALPHA`and`BETA`are scalars,`A`and`B`are`N x K`or`K x N`matrices, and`C`is an`N x N`symmetric matrix.

`zsyr2k:`procedure`xSYR2K`performs one of the symmetric rank 2k operations`C := alpha*A*B' + beta*C`or`C := alpha*B'*A + beta*C`.`ALPHA`and`BETA`are scalars,`A`and`B`are`N x K`or`K x N`matrices, and`C`is an`N x N`symmetric matrix.