High speed emulation of arithmetic operations
AssigneeUnisys Corporation
InventorsDavid Michael Dahm, Michael James Irving
Life of this patent
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Abstract
A method of executing arithmetic operations in a data processing apparatus wherein first and second numbers having a main frame “e-mode format are converted to IEEE double format. Arithmetic operations are then performed using the first and second numbers in IEEE double format to form a result in IEEE double format. The IEEE double format result is then converted back to main frame e-mode format. The conversion of the first and second e-mode numbers to IEEE format includes a step of shifting a mantissa of each e-mode number by a single step of subtracting 2Nexp where Nexp is the exponent of the IEEE double under formation.
Claims24
A method of emulating an arithmetic operation in a main-frame computer using a processor, the method comprising:
- converting a first number in main frame format to a second number in IEEE double format using the processor, each of the first and second numbers including a respective exponent and mantissa, the converting comprising:
- computing the mantissa of the second number by subtracting a quantity from the mantissa of the first number using the processor, the subtraction resulting in a shift of the mantissa of the first number;
- and
- computing the exponent of the second number based on the exponent of the first number using the processor;
- performing the arithmetic operation on the second number using the processor, resulting in a third number in IEEE double format;
- and
- converting the third number to a fourth number in main frame format using the processor.
A method of emulating an arithmetic operation in a main-frame computer using a processor, the method comprising:
- performing the arithmetic operation on a first number in IEEE double format using the processor, resulting in a second number in IEEE double format;
- and
- converting the second number in IEEE double format to a third number in main frame format using the processor, each of the second and third numbers including a respective exponent and mantissa, the converting comprising:
- computing the exponent of the third number by dividing the exponent of the second number by 3 and subtracting 353 from the result;
- and
- computing the mantissa of the third number by shifting the mantissa of the second number by S bits where S=16−Nexp mod 3, where Nexp is the exponent of the second number.
An article of manufacture comprising:
- a computer readable medium;
- and
- computer readable program code embodied in the computer usable medium for converting a number from a main frame format to IEEE double format, each of the main frame format and the IEEE double format including a respective exponent and mantissa, the computer readable program code comprising:
- computer readable program code for computing the mantissa of the IEEE double format number by subtracting a quantity from the mantissa of the main frame format number, the subtraction resulting in a shift of the mantissa of the main frame format number.
An article of manufacture comprising:
- a computer usable medium;
- and
- computer readable program code embodied in the computer usable medium for converting an IEEE double format number to main frame format number, each of the main frame format number and the IEEE double format number including a respective exponent and mantissa, the computer readable program code comprising:
- computer readable program code for computing the exponent of the main frame format number by dividing the exponent of the IEEE double format number by 3 and subtracting 353 from the result;
- and
- computer readable program code for computing the mantissa of the main frame format number by shifting a mantissa of the IEEE double format number by S bits where S=16−Nexp mod3, where Nexp is the exponent of the IEEE double format number.
A storage medium encoded with machine-readable computer program code executable by a computer to perform a method for converting a number from a main frame format to IEEE double format, each of the main frame format and the IEEE double format including a respective exponent and mantissa, the method comprising the step of:
- computing the mantissa of the IEEE double format number by subtracting a quantity from the mantissa of the main frame format number, the subtraction resulting in a shift of the mantissa of the main frame format number.
A storage medium encoded with machine-readable computer program code executable by a computer to perform a method for converting a number from an IEEE double format to a main frame format, the method comprising the steps of:
- computing an exponent of a main frame format number by dividing an exponent of an IEEE double number by 3 and subtracting 353 from the dividend;
- and
- a shifting a mantissa of the main frame format number by S bits where S=16−Nexp mod3, where Nexp is an exponent of the IEEE double number.
Dependencies are inferred from the claim text.