Problems With Data Dependencies
Executing instructions in parallel (i.e. simultaneously) raises problems with data dependencies, meaning that some instructions may be dependent on the results of others, and hence care must be taken to execute in the correct order.
Take for example these sequence of instructions:
r1 = r2 + r3
r7 = r1 + r4
We have a RAW (Read After Write) data dependency here, meaning that we must wait for instruction 1 to finish before executing instruction 2, as we require the correct value of r1 (register 1). Hence these instruction cannot be executed simultaneously.
Read more about this topic: Shelving Buffer
Famous quotes containing the words problems with, problems and/or data:
“The mother’s and father’s attitudes toward the child correspond to the child’s own needs.... Mother has the function of making him secure in life, father has the function of teaching him, guiding him to cope with those problems with which the particular society the child has been born into confronts him.”
—Erich Fromm (1900–1980)
“I rarely speak about God. To God, yes. I protest against Him. I shout at Him. But to open a discourse about the qualities of God, about the problems that God imposes, theodicy, no. And yet He is there, in silence, in filigree.”
—Elie Wiesel (b. 1928)
“To write it, it took three months; to conceive it three minutes; to collect the data in it—all my life.”
—F. Scott Fitzgerald (1896–1940)